EMBRYOPSIDA Pirani & Prado
Gametophyte dominant, independent, multicellular, initially ±globular, not motile, branched; showing gravitropism; acquisition of phenylalanine lysase* [PAL], flavonoid synthesis*, microbial terpene synthase-like genes +, triterpenoids produced by CYP716 enzymes, CYP73 and phenylpropanoid metabolism [development of phenolic network], xyloglucans in primary cell wall, side chains charged; plant poikilohydrous [protoplasm dessication tolerant], ectohydrous [free water outside plant physiologically important]; thalloid, leafy, with single-celled apical meristem, tissues little differentiated, rhizoids +, unicellular; chloroplasts several per cell, pyrenoids 0; glycolate metabolism in leaf peroxisomes [glyoxysomes]; centrioles/centrosomes in vegetative cells 0, microtubules with γ-tubulin along their lengths [?here], interphase microtubules form hoop-like system; metaphase spindle anastral, predictive preprophase band + [with microtubules and F-actin; where new cell wall will form], phragmoplast + [cell wall deposition centrifugal, from around the anaphase spindle], plasmodesmata +; antheridia and archegonia +, jacketed*, surficial; mblepharoplast +, centrioles develop de novo, bicentriole pair coaxial, separate at midpoint, centrioles rotate, associated with basal bodies of cilia, multilayered structure + [4 layers: L1, L4, tubules; L2, L3, short vertical lamellae] (0), spline + [tubules from L1 encircling spermatid], basal body 200-250 nm long, associated with amorphous electron-dense material, microtubules in basal end lacking symmetry, stellate array of filaments in transition zone extended, axonemal cap 0 [microtubules disorganized at apex of cilium]; male gametes [spermatozoids] with a left-handed coil, cilia 2, lateral; oogamy; sporophyte +*, multicellular, growth 3-dimensional*, cuticle +*, plane of first cell division transverse [with respect to long axis of archegonium/embryo sac], sporangium and upper part of seta developing from epibasal cell [towards the archegonial neck, exoscopic], with at least transient apical cell [?level], initially surrounded by and dependent on gametophyte, placental transfer cells +, in both sporophyte and gametophyte, wall ingrowths develop early; suspensor/foot +, cells at foot tip somewhat haustorial; sporangium +, single, terminal, dehiscence longitudinal; meiosis sporic, monoplastidic, MTOC [= MicroTubule Organizing Centre] associated with plastid, sporocytes 4-lobed, cytokinesis simultaneous, preceding nuclear division, quadripolar microtubule system +; wall development both centripetal and centrifugal, 1000 spores/sporangium, sporopollenin in the spore wall* laid down in association with trilamellar layers [white-line centred lamellae; tripartite lamellae]; plastid transmission maternal; nuclear genome [1C] <1.4 pg, main telomere sequence motif TTTAGGG, KNOX1 and KNOX2 [duplication] and LEAFY genes present, ethylene involved in cell elongation; chloroplast genome with close association between trnLUAA and trnFGAA genes [precursors for starch synthesis], tufA, minD, minE genes moved to nucleus; mitochondrial trnS(gcu) and trnN(guu) genes +.
Many of the bolded characters in the characterization above are apomorphies of more or less inclusive clades of streptophytes along the lineage leading to the embryophytes, not apomorphies of crown-group embryophytes per se.
All groups below are crown groups, nearly all are extant. Characters mentioned are those of the immediate common ancestor of the group,  contains explanatory material, () features common in clade, exact status unclear.
Sporophyte well developed, branched, branching dichotomous, potentially indeterminate; hydroids +; stomata on stem; sporangia several, terminal; spore walls not multilamellate [?here].
II. TRACHEOPHYTA / VASCULAR PLANTS
Sporophyte long lived, cells polyplastidic, photosynthetic red light response, stomata open in response to blue light; plant homoiohydrous [water content of protoplasm relatively stable]; control of leaf hydration passive; plant endohydrous [physiologically important free water inside plant]; PIN[auxin efflux facilitators]-mediated polar auxin transport; (condensed or nonhydrolyzable tannins/proanthocyanidins +); xyloglucans with side chains uncharged [?level], in secondary walls of vascular and mechanical tissue; lignins +; roots +, often ≤1 mm across, root hairs and root cap +; stem apex multicellular [several apical initials, no tunica], with cytohistochemical zonation, plasmodesmata formation based on cell lineage; vascular development acropetal, tracheids +, in both protoxylem and metaxylem, G- and S-types; sieve cells + [nucleus degenerating]; endodermis +; stomata numerous, involved in gas exchange; leaves +, vascularized, spirally arranged, blades with mean venation density ca 1.8 mm/mm2 [to 5 mm/mm2], all epidermal cells with chloroplasts; sporangia in strobili, sporangia adaxial, columella 0; tapetum glandular; sporophyte-gametophyte junction lacking dead gametophytic cells, mucilage, ?position of transfer cells; MTOCs not associated with plastids, basal body 350-550 nm long, stellate array in transition region initially joining microtubule triplets; archegonia embedded/sunken [only neck protruding]; embryo suspensor +, shoot apex developing away from micropyle/archegonial neck [from hypobasal cell, endoscopic], root lateral with respect to the longitudinal axis of the embryo [plant homorhizic].[MONILOPHYTA + LIGNOPHYTA]
Sporophyte growth ± monopodial, branching spiral; roots endomycorrhizal [with Glomeromycota], lateral roots +, endogenous; G-type tracheids +, with scalariform-bordered pits; leaves with apical/marginal growth, venation development basipetal, growth determinate; sporangium dehiscence by a single longitudinal slit; cells polyplastidic, MTOCs diffuse, perinuclear, migratory; blepharoplasts +, paired, with electron-dense material, centrioles on periphery, male gametes multiciliate; nuclear genome [1C] 7.6-10 pg [mode]; chloroplast long single copy ca 30kb inversion [from psbM to ycf2]; mitochondrion with loss of 4 genes, absence of numerous group II introns; LITTLE ZIPPER proteins.
Sporophyte woody; stem branching lateral, meristems axillary; lateral root origin from the pericycle; cork cambium + [producing cork abaxially], vascular cambium bifacial [producing phloem abaxially and xylem adaxially].
SEED PLANTS† / SPERMATOPHYTA†
Growth of plant bipolar [plumule/stem and radicle/root independent, roots positively geotropic]; plants heterosporous; megasporangium surrounded by cupule [i.e. = unitegmic ovule, cupule = integument]; pollen lands on ovule; megaspore germination endosporic [female gametophyte initially retained on the plant].
EXTANT SEED PLANTS
Plant evergreen; nicotinic acid metabolised to trigonelline, (cyanogenesis via tyrosine pathway); microbial terpene synthase-like genes 0; primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignin chains started by monolignol dimerization [resinols common], particularly with guaiacyl and p-hydroxyphenyl [G + H] units [sinapyl units uncommon, no Maüle reaction]; roots often ≥1 mm across, stele diarch to pentarch, xylem and phloem originating on alternating radii, cork cambium deep seated; stem apical meristem complex [with quiescent centre, etc.], plasmodesma density in SAM 1.6-6.2[mean]/μm2 [interface-specific plasmodesmatal network]; eustele +, protoxylem endarch, endodermis 0; wood homoxylous, tracheids and rays alone, tracheid/tracheid pits circular, bordered; mature sieve tube/cell lacking functioning nucleus, sieve tube plastids with starch grains; phloem fibres +; cork cambium superficial; leaf nodes 1:1, a single trace leaving the vascular sympodium; leaf vascular bundles amphicribral; guard cells the only epidermal cells with chloroplasts, stomatal pore with active opening in response to leaf hydration, control by abscisic acid, metabolic regulation of water use efficiency, etc.; axillary buds +, exogenous; prophylls two, lateral; leaves with petiole and lamina, development basipetal, lamina simple; sporangia borne on sporophylls; spores not dormant; microsporophylls aggregated in indeterminate cones/strobili; grains monosulcate, aperture in ana- position [distal], primexine + [involved in exine pattern formation with deposition of sporopollenin from tapetum there], exine and intine homogeneous, exine alveolar/honeycomb; ovules with parietal tissue [= crassinucellate], megaspore tetrad linear, functional megaspore single, chalazal, sporopollenin 0; gametophyte ± wholly dependent on sporophyte, development initially endosporic [apical cell 0, rhizoids 0, etc.]; male gametophyte with tube developing from distal end of grain, male gametes two, developing after pollination, with cell walls; female gametophyte initially syncytial, walls then surrounding individual nuclei; embryo cellular ab initio, suspensor short-minute, embryonic axis straight [shoot and root at opposite ends], primary root/radicle produces taproot [= allorhizic], cotyledons 2; embryo ± dormant; chloroplast ycf2 gene in inverted repeat, trans splicing of five mitochondrial group II introns, rpl6 gene absent; ??whole nuclear genome duplication [ζ - zeta - duplication], 2C genome size (0.71-)1.99(-5.49) pg, two copies of LEAFY gene, PHY gene duplications [three - [BP [A/N + C/O]] - copies], 5.8S and 5S rDNA in separate clusters.
IID. ANGIOSPERMAE / MAGNOLIOPHYTA
Lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, apigenin and/or luteolin scattered, [cyanogenesis in ANA grade?], lignin also with syringyl units common [G + S lignin, positive Maüle reaction - syringyl:guaiacyl ratio more than 2-2.5:1], hemicelluloses as xyloglucans; root cap meristem closed (open); pith relatively inconspicuous, lateral roots initiated immediately to the side of [when diarch] or opposite xylem poles; epidermis probably originating from inner layer of root cap, trichoblasts [differentiated root hair-forming cells] 0, hypodermis suberised and with Casparian strip [= exodermis]; shoot apex with tunica-corpus construction, tunica 2-layered; starch grains simple; primary cell wall mostly with pectic polysaccharides, poor in mannans; tracheid:tracheid [end wall] plates with scalariform pitting, multiseriate rays +, wood parenchyma +; sieve tubes enucleate, sieve plates with pores (0.1-)0.5-10< µm across, cytoplasm with P-proteins, not occluding pores of plate, companion cell and sieve tube from same mother cell; ?phloem loading/sugar transport; nodes 1:?; dark reversal Pfr → Pr; protoplasm dessication tolerant [plant poikilohydric]; stomata randomly oriented, brachyparacytic [ends of subsidiary cells ± level with ends of guard cells], outer stomatal ledges producing vestibule, reduction in stomatal conductance with increasing CO2 concentration; lamina formed from the primordial leaf apex, margins toothed, development of venation acropetal, overall growth ± diffuse, secondary veins pinnate, fine venation hierarchical-reticulate, (1.7-)4.1(-5.7) mm/mm2, vein endings free; flowers perfect, pedicellate, ± haplomorphic, protogynous; parts free, numbers variable, development centripetal; P = T, petal-like, each with a single trace, outer members not sharply differentiated from the others, not enclosing the floral bud; A many, filament not sharply distinguished from anther, stout, broad, with a single trace, anther introrse, tetrasporangiate, sporangia in two groups of two [dithecal], each theca dehiscing longitudinally by a common slit, ± embedded in the filament, walls with at least outer secondary parietal cells dividing, endothecium +, cells elongated at right angles to long axis of anther; tapetal cells binucleate; microspore mother cells in a block, microsporogenesis successive, walls developing by centripetal furrowing; pollen subspherical, tectum continuous or microperforate, ektexine columellate, endexine lamellate only in the apertural regions, thin, compact, intine in apertural areas thick, orbicules +, pollenkitt +; nectary 0; carpels present, superior, free, several, spiral, ascidiate [postgenital occlusion by secretion], stylulus at most short [shorter than ovary], hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, carinal, dry; suprastylar extragynoecial compitum +; ovules few [?1]/carpel, marginal, anatropous, bitegmic, micropyle endostomal, outer integument 2-3 cells across, often largely subdermal in origin, inner integument 2-3 cells across, often dermal in origin, parietal tissue 1-3 cells across, nucellar cap?; megasporocyte single, hypodermal, functional megaspore lacking cuticle; female gametophyte lacking chlorophyll, four-celled [one module, egg and polar nuclei sisters]; ovule not increasing in size between pollination and fertilization; pollen grains bicellular at dispersal, germinating in less than 3 hours, siphonogamy, pollen tube unbranched, growing towards the ovule, between cells, growth rate (20-)80-20,000 µm/hour, apex of pectins, wall with callose, lumen with callose plugs, penetration of ovules via micropyle [porogamous], whole process takes ca 18 hours, distance to first ovule 1.1-2.1 mm; male gametophytes tricellular, gametes 2, lacking cell walls, ciliae 0, double fertilization +, ovules aborting unless fertilized; fruit indehiscent, P deciduous; mature seed much larger than fertilized ovule, small [<5 mm long], dry [no sarcotesta], exotestal; endosperm +, ?diploid [one polar nucleus + male gamete], cellular, development heteropolar [first division oblique, micropylar end initially with a single large cell, divisions uniseriate, chalazal cell smaller, divisions in several planes], copious, oily and/or proteinaceous, embryo short [<¼ length of seed]; plastid and mitochondrial transmission maternal; Arabidopsis-type telomeres [(TTTAGGG)n]; nuclear genome [2C] (0.57-)1.45(-3.71) [1 pg = 109 base pairs], ??whole nuclear genome duplication [ε/epsilon event]; ndhB gene 21 codons enlarged at the 5' end, single copy of LEAFY and RPB2 gene, knox genes extensively duplicated [A1-A4], AP1/FUL gene, palaeo AP3 and PI genes [paralogous B-class genes] +, with "DEAER" motif, SEP3/LOFSEP and three copies of the PHY gene, [PHYB [PHYA + PHYC]]; chloroplast chlB, -L, -N, trnP-GGG genes 0.
[NYMPHAEALES [AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]]: wood fibres +; axial parenchyma diffuse or diffuse-in-aggregates; pollen monosulcate [anasulcate], tectum reticulate-perforate [here?]; ?genome duplication; "DEAER" motif in AP3 and PI genes lost, gaps in these genes.
[AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: phloem loading passive, via symplast, plasmodesmata numerous; vessel elements with scalariform perforation plates in primary xylem; essential oils in specialized cells [lamina and P ± pellucid-punctate]; tension wood + [reaction wood: with gelatinous fibres, G-fibres, on adaxial side of branch/stem junction]; anther wall with outer secondary parietal cell layer dividing; tectum reticulate; nucellar cap + [character lost where in eudicots?]; 12BP [4 amino acids] deletion in P1 gene.
[[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]] / MESANGIOSPERMAE: benzylisoquinoline alkaloids +; sesquiterpene synthase subfamily a [TPS-a] [?level], polyacetate derived anthraquinones + [?level]; outer epidermal walls of root elongation zone with cellulose fibrils oriented transverse to root axis; P more or less whorled, 3-merous [?here]; pollen tube growth intra-gynoecial; extragynoecial compitum 0; carpels plicate [?here]; embryo sac monosporic [spore chalazal], 8-celled, bipolar [Polygonum type], antipodal cells persisting; endosperm triploid.
[MONOCOTS [CERATOPHYLLALES + EUDICOTS]]: (veins in lamina often 7-17 mm/mm2 or more [mean for eudicots 8.0]); (stamens opposite [two whorls of] P); (pollen tube growth fast).
[CERATOPHYLLALES + EUDICOTS]: ethereal oils 0 [or next node up]; fruit dry [very labile].
EUDICOTS: (Myricetin +), asarone 0 [unknown in some groups, + in some asterids]; root epidermis derived from root cap [?Buxaceae, etc.]; (vessel elements with simple perforation plates in primary xylem); nodes 3:3; stomata anomocytic; flowers (dimerous), cyclic; protandry common; K/outer P members with three traces, ("C" +, with a single trace); A ?, filaments fairly slender, anthers basifixed; microsporogenesis simultaneous, pollen tricolpate, apertures in pairs at six points of the young tetrad [Fischer's rule], cleavage centripetal, wall with endexine; G with complete postgenital fusion, stylulus/style solid [?here]; seed coat?
[PROTEALES [TROCHODENDRALES [BUXALES + CORE EUDICOTS]]]: (axial/receptacular nectary +).
[TROCHODENDRALES [BUXALES + CORE EUDICOTS]]: benzylisoquinoline alkaloids 0; euAP3 + TM6 genes [duplication of paleoAP3 gene: B class], mitochondrial rps2 gene lost.
[BUXALES + CORE EUDICOTS]: mitochondrial rps11 gene lost.
CORE EUDICOTS / GUNNERIDAE: (ellagic and gallic acids +); leaf margins serrate; compitum + [one position]; micropyle?; γ whole nuclear genome duplication [palaeohexaploidy, gamma triplication], x = 21, 2C genome size (0.79-)1.05(-1.41) pg, PI-dB motif +; small deletion in the 18S ribosomal DNA common.
[ROSIDS ET AL. + ASTERIDS ET AL.] / PENTAPETALAE: root apical meristem closed; (cyanogenesis also via [iso]leucine, valine and phenylalanine pathways); flowers rather stereotyped: 5-merous, parts whorled; P = K + C, K enclosing the flower in bud, with three or more traces, C with single trace; A = 2x K/C, in two whorls, internal/adaxial to C, alternating, (numerous, but then usually fasciculate and/or centrifugal); pollen tricolporate; G [(3, 4) 5], whorled, placentation axile, style +, stigma not decurrent, compitum + [another position]; endosperm nuclear; fruit dry, dehiscent, loculicidal [when a capsule]; floral nectaries with CRABSCLAW expression.
[DILLENIALES [SAXIFRAGALES + ROSIDS]]: stipules + [usually apparently inserted on the stem].
[SAXIFRAGALES + ROSIDS] / ROSANAE Takhtajan / SUPERROSIDAE: ??
ROSIDS / ROSIDAE: anthers ± dorsifixed, transition to filament narrow, connective thin.
[ROSID I + ROSID II]: (mucilage cells with thickened inner periclinal walls and distinct cytoplasm); if nectary +, usu. receptacular; embryo long; chloroplast infA gene defunct, mitochondrial coxII.i3 intron 0.
ROSID I / FABIDAE / [ZYGOPHYLLALES [the COM clade + the nitrogen-fixing clade]]: endosperm scanty.
[the COM clade + the nitrogen-fixing clade]: ?
[FABALES [ROSALES [CUCURBITALES + FAGALES]]] / the nitrogen-fixing clade / fabids: (N-fixing by associated root-dwelling bacteria); tension wood +; seed exotestal.
[ROSALES [CUCURBITALES + FAGALES]]: (actinomycete Frankia infection +); styles separate; ovules 1-2/carpel, apical.
Age. This node is estimated to be (110-)105(-100) or (94-)89(-84) Ma (H. Wang et al. 2009); a very different age of around 429-199 Ma is suggested by Jeong et al. (1999), while ages of around 92.2-78.9 Ma are offered by Naumann et al. (2013), of (110-)97(-92) Ma by Bell et al. (2010: c.f. topology), about 106.4Ma by Tank et al. (2015: Table S1), of around 107.4 Ma by Hohmann et al. (2015), of about 113 Ma by Foster et al. (2016a: q.v. for details), and of ca 126 Ma by Z. Wu et al. (2014).
Evolution: Divergence & Distribution. It is difficult to optimize ovule number in this part of the tree; see also D. W. Taylor et al. (2012) for possible apomorphies. The character "fruit indehiscent" could be placed at this node rather than the next one up, but since the gynoecial morphology at the two nodes is likely to be rather different, I did not place the dehiscence feature here.
Ecology & Physiology. Nitrogen fixing in this clade usually involves symbioses with the actinomycete Frankia rather than with rhizobia, and this is discussed further on the Fabales page.
Bacterial/Fungal Associations. Rose (1980) noted that vesicular-arbuscular mycorrhizae co-occurred on all plants with actinorrhizal Frankia nitrogen fixation that she studied - seven families, 7+ origins of the associations, and in four there were also/only associations with ectomycorrhizal fungi.
Phylogeny. For relationships, see above.
ROSALES Perleb - Main Tree.
(Isoflavonoids, dihydroflavonols +); mucilage cells +; roots diarch [lateral roots 4-ranked]; prismatic crystals in ray cells [not Barbeyaceae, Elaeagnaceae]; (sieve tubes with non-dispersive protein bodies, lacking starch or protein inclusions); inflorescence cymose; hypanthium +, nectariferous, K valvate, C clawed; stigma dry; ovule 1/carpel, epitropous, micropyle endostomal; fruit indehiscent, K and/or hypanthium persistent; (polyembryony +); 4bp duplication near 3' end of chloroplast rbcL gene. - 9 families, 263 genera, 8,010 species.
Note: In all node characterizations, boldface denotes a possible apomorphy, (....) denotes a feature the exact status of which in the clade is uncertain, [....] includes explanatory material; other text lists features found pretty much throughout the clade. Note that the particular node to which many characters, particularly the more cryptic ones, should be assigned is unclear. This is partly because homoplasy is very common, in addition, basic information for all too many characters is very incomplete, frequently coming from taxa well embedded in the clade of interest and so making the position of any putative apomorphy uncertain. Then there are the not-so-trivial issues of how character states are delimited and ancestral states are reconstructed (see above).
Age. Wikström et al. (2001) dated crown Rosales at (79-)76(-73) Ma, while other estimates are rather older: (96-)93, 88(-85) Ma (two penalized likelihood dates, Bayesian relaxed clock estimates to 103 My: H. Wang et al. 2009), ca 94 Ma (Magallón & Castillo 2009), (104-)85, 82(-73) Ma (Bell et al. 2010) and ca 97 Ma (Z. Wu et al. 2014). However, the estimate in Xue et al. (2012) is only 40.8 or 31.9 Ma, that in Hohmann et al. (2015) is ca 87.7 Ma, in Tank et al. (2015: Table S2) is ca 89.4 Ma, in Q. Zhang et al. (2018) is (107-)105.5(-102.8) Ma, and in H.-L. Li et al. (2015) it is (112.6-)106.5, 106.1(-100.2) Ma, while that in Jeong et al. (1999) is 367-170 Ma, so take your pick.
Evolution: Divergence & Distribution. Rosales contain ca 1.9% of eudicot diversity (Magallón et al. 1999).
Ronse De Craene (2003, see also 2010) suggested that loss of petals might characterise Rosales, with apparent "petals" occupying the position of stamens and their evolution allowing e.g. Rosaceae to diversify. However, if Rosales are sister to Fabales, as Ronse de Craene (2003) thought, they are not a notably diverse group in terms of species numbers, the more so since almost 4,000 species of Rosales - about half - are in the Ulmaceae-Urticaceae group, which lack petals of any sort. The Ulmaceae-Urticaceae group forms a well-supported clade, and the wind pollination that is so common there cannot be considered basic to Rosales as a whole (c.f. Ronse de Craene 2010). Even with the relationships [Rosales [Cucurbitales + Fagales]] (see above) it seems that no argument connecting petals in Rosales with diversity can be made (see also Ronse de Craene & Brockington 2013).
A granular exine infratectum may be a synapomorphy for the clade (see also Doyle 2009); here it is placed as a synapomorphy for the [Ulmaceae [Cannabaceae [Moraceae + Urticaceae]]] clade, but it is found elsewhere in the order, too.
Ecology & Physiology. For nitrogen fixation by Frankia, see elsewhere.
Plant-Animal Interactions. Quite a number of butterfly larvae - especially caterpillars of "basal" groups and Lycaeninae - feed here (Fiedler 1995; Janz & Nylin 1998).
Bacterial/Fungal Associations. Some taxa in at least Rosaceae, Rhamnaceae, Elaeagnaceae and Ulmaceae are ectomycorrhizal (see Malloch et al. 1980; Rose 1980; S. E. Smith and Read 1997). For a summary of what is known about nitrogen fixation in this clade, see Santi et al. (2013).
Genes & Genomes. The position of the duplication that resulted in two copies of the granule bound starch synthase I (gbss I) nuclear gene is unclear; two copies are found in all Rosaceae, but also in Frangula (Rhamnaceae) (Evans & Campbell 2002).
Soltis et al. (1995b) noted that there was a duplication in the chloroplast rbcL gene; it was absent from the other rosids they examined.
Chemistry, Morphology, etc. Roots are commonly diarch in Rosaceae, but are also tetrarch, etc.; sampling elsewhere is poor, although less so in Ulmaceae and relatives, and diarch roots are found throughout the order. Tracheary members in Rosaceae commonly have pseudotori (thickenings in pit membranes associated with plasmodesmata), while true tori occur in Rosaceae (Cercocarpus) and also Cannabaceae and Ulmaceae (Jansen et al. 2007; Coleman et al. 2004; Dute 2015), although these tori are formed in two different ways (Dute et al. 2010a) and the torus is only weakly lignified. Sieve tube plastids lacking both starch and protein inclusions are quite common in Rosales, although they are rare outside (Behnke 1991a) and the sieve tubes quite often have non-dispersive protein bodies, although not in Rhamnaceae (Behnke 1973). For polyembryony, sporadic here, see G. Dahlgren (1991).
Kubitzki (2004) provides a summary of the order; there is much useful information in Thulin et al. (1998).
Phylogeny. In early molecular studies Rosaceae appeared as sister to the rest of the order (strong support: Savolainen et al. 2000a; Wang et al. 2009), while Ulmaceae and relatives (the old Urticales) and Rhamnaceae and relatives formed two clades (also Thulin et al. 1998; Savolainen et al. 2000b; Richardson et al. 2000b; Sytsma et al. 2002: position of Rosaceae, etc., uncertain; Wang et al. 2009; Soltis et al. 2011), as in the tree below. The position of Elaeagnaceae was sometimes rather labile (Richardson et al. 2000b: successive approximation weighting), even being embedded in Rhamnaceae in a rbcL analysis, and there was quite strong support for a clade [Barbeyaceae + Dirachmaceae]. S.-D. Zhang et al. (2011) looked at variation in twelve genes (10 from the plastids) in 25 taxa of Rosales, and the major relationships within the order are very well supported, although somewhat less so in the subclade that includes Rhamnaceae; the relationships that Zhang et al. (2011) found are followed here.
This grouping is suggested by C. S. Campbell (pers. comm. 2003), Sytsma et al. (2002: support weak) and especially S.-D. Zhang et al. (2011). Rhamnaceae, Barbeyaceae and Dirachmaceae may form a clade (Richardson et al. 2000a). However, this was not confirmed by Zhang et al. (2011), but the maximum parsimony bootstrap values for the relationships there are not strong, nor is the maximum likelihood support for [Elaeagnaceae [Barbeyaceae + Dirachmaceae]], although posterior probabilities are all 1.0. H.-L. Li et al. (2015) and M. Sun et al. (2016) found weak support for the relationships [Dirachmaceae [Rhamnaceae [Barbeuiaceae + Elaeagnaceae]]].
For relationships in the Ulmaceae-Moraceae area, see the phylogenies suggested by Sytsma et al. (2000) and Song et al. (2001), and they place Cannabis within the old Celtidaceae (see also e.g. Ueda et al. 1997b); Cannabaceae is the earliest name for the combined group. They also place Cecropia within Urticaceae, and this set of relationships has been strongly supported by a more comprehensive analysis (Sytsma 2002) and other studies since. See H.-L. Li (2015), M. Sun et al. (2016) and Z.-D. Chen et al. (2016) for quite comprehensive molecular phylogenies of the whole group, Judd et al. (1994) for a morphological phylogeny, and Zavada and Kim (1996) for a molecular phylogeny focussed on the old paraphyletic Ulmaceae s.l..
There is also the issue of the placement of the holoparasitic Cynomoriaceae. Z.-H. Zhang et al. (2009; see also Moore et al. 2011) placed Cynomoriaceae in Rosales and sister to Rosaceae based on analyses of chloroplast inverted repeat sequences; support was strong, but Moraceae were the only other family in the order examined. However, there are problems with this analysis (see Bellot et al. 2016) and Cynomoriaceae are to be included in Saxifragales, q.v. for further details.
Previous Relationships. In the past, Urticales (Urticaceae, Moraceae, etc.) were kept well separate from Rosaceae, largely because their very reduced and usually wind-pollinated flowers suggested relationships to the old Amentiferae.
Includes Barbeyaceae, Cannabaceae, Dirachmaceae, Elaeagnaceae, Moraceae, Rhamnaceae, Rosaceae, Ulmaceae, Urticaceae.
Synonymy: Rhamnineae Shipunov - Amygdalales Link, Artocarpales Martius, Barbeyales Takhtajan & Reveal, Cannabales Döll, Dryadales Link, Elaeagnales Berchtold & J. Presl, Ficales Dumortier, Frangulales Wirtgen, Morales Martius, Rhamnales Link, Sanguisorbales Link, Spiraeales Link, Ulmales Link, Urticales Berchtold & J. Presl - Barbeyanae Reveal & Doweld, Rhamnanae Reveal, Rosanae Takhtajan, Urticanae Reveal - Frangulopsida Endlicher, Rhamnopsida Brongniart, Rosopsida Batsch Urticopsida Bartling - Rosidae Takhtajan
ROSACEAE Jussieu, nom. cons. - Back to Rosales
Triterpenes +, alkaloids 0; cork deep seated; (vessel elements with scalariform perforation plates); (true) and fibre tracheids +; petiole vasculature of arcuate or annular bundles, or annular; leaves spiral (opposite), lamina vernation usu. conduplicate, (secondary veins palmate), stipules often petiolar; inflorescences racemose (determinate); flowers protogynous or condition ± undecided; (C 0); A (1-)15-many [ca 20 common - 10 + 5 + 5, centripetal, in groups], (latrorse); (pollen porate); G free, stigmas punctate to expanded, or decurrent down stylulus, compitum 0; ovules with parietal tissue 2-4 cells across, nucellar cap ca 4 cells across; megaspore mother cells several; fruit aggregate of achenes; exotestal cells periclinally elongated, radial walls thickened, or palisade or tabular, walls with spiral or reticulate thickenings, outer wall often becoming mucilaginous, endotegmic cells slightly thickened, or seed coat undistinguished; chalazal endosperm haustorium +; x = 9; genome size [2C] (0.2-)0.42-3.0 pg, duplication of GBSSI [granule bound starch synthase I] gene.
92 [list]/2,805 [species numbers in particular ± notional]. World-wide, but esp. N. hemisphere, often not deserts or tropical rainforest (map: from Vester 1940 [overly optimistic - or inc. Chrysobalanaceae?]; Hultén 1971; Trop. Afr. Fl. Pl. Ecol. Distr. 2. 2006; FloraBase i.2013; Australia's Virtual Herbarium i.2013). [Photos - Collection, Collection.]
Age. Crown-group Rosaceae are dated to (92.8-)88.3(-84.2) Ma (Chin et al. 2014), around 61.2 Ma (Hohmann et al. 2015), or as little as ca 46 Ma (Murat et al. 2015b); also 76.9 Ma (Dobes & Paul 2010), or as much as 108-93 Ma (Töpel et al. 2012), (103-)92.2(-85.8) Ma (Gehrke et al. 2015) or ca 101.6 Ma (Y. Xiang et al. 2016) - see also S.-D. Zhang et al. (2017) for more dates, and who offer an age of ca 95.1 Ma themselves.
Turonian fossils some 90 Ma old are assignable to Rosaceae (Crepet et al. 2004 for references).
[Dryadoideae + Rosoideae]: ?
Age. Divergence at this node is dated to (96.1-)87.6, 86.1(-63.3) Ma (H.-L. Li et al. 2015) or (94.3-)92.9(-92.1) Ma (S.-D. Zhang et al. 2017).
1. Dryadoideae Juel
Association with N-fixing Frankia, (ectomycorrhizal); sugar alcohol sorbitol [carbohydrate transport], cyanogenic glycosides [dhurrin] +; (torus-margo pits + - Cercocarpus); leaves usu. simple; G 1-many; ovules straight (anatropous, apotropous - Dryas), (with chalazal projection - Cercocarpus); styles persistent, hairy (no styles).
4/19: Cercocarpus (8). W. North America, Dryas circumboreal.
Age. Crown-group Dryadoideae are dated to ca 73 Ma Zanne et al. 2014; see Tedersoo & Brundrett 2017), (83.2-)63.1(-44.7) Ma (Chin et al. 2014), (48.7-)40.7(-39.7) Ma (S.-D. Zhang et al. 2017) or ca 38 Ma (Y. Xiang et al. 2016).
Synonymy: Cercocarpaceae J. Agardh, Dryadaceae Gray
2. Rosoideae Arnott
Herbs to shrubs; 2-pyrone-4,6dicarboxylic acid, ellagic acid +; rays often narrow; cuticle waxes as narrow ribbons and triangular rodlets; leaves usu. compound; (epicalyx +), carpels many; fruits usu. achenes or drupelets; ovule (straight), unitegmic; x = 7; plant with phragmidiaceous rusts.
21/2,187. Especially temperate (to Arctic) areas.
Age. Crown-group Rosoideae (note sampling) are dated to (83.2-)71.1(-64.3) Ma (Chin et al. 2014) or ca 82 Ma (Y. Xiang et al. 2016); other dates are 66.5-50 Ma (Dobes & Paul 2010), (78.1-)75.8(-74.5) Ma (S.-D. Zhang et al. 2017), 95-70 Ma (Topel et al. 2010) and (75.8-)65.5(-55.2) or 43.8-36.5 Ma (Gehrke et al. 2015).
2A. Ulmarieae Lamarck & de Candolle
Plant herbaceous; receptacle enlarged; ovules 2/carpel, superposed.
Synonymy: Ulmariaceae Gray
Rosodeae T. Eriksson, Smedmark, & M. S. Kerr / [Rubeae [Colurieae [Roseae [Potentilleae + Agrimonieae]]]]: ?
Age. This node can be dated to ca 75 Ma (Y. Xiang et al. 2016).
2B. Rubeae Dumortier
Prickly scrambling shrub; receptacle enlarged; ovules 2/carpel, collateral, integument ca 6 cells across; fruit an aggregate of drupelets.
1/±250-800<. ± Worldwide, esp. N. Temperate.
Synonymy: Chamaemoraceae Lilja
[Colurieae [Roseae [Potentilleae + Agrimonieae]]]: ?
2C. Colurieae Rydberg
Ovule apotropous [Geum]; seed coat vascularized [Waldsteinia].
3/42: Geum (40). Temperate, inc. montane tropics, Chile.
[Roseae [Potentilleae + Agrimonieae]]: ?
Age. The age of this clade is (86.2-)73.8(-61.2) Ma (Töpel et al. 2012).
2D. Roseae Lamarck & de Candolle
Prickly arching shrub; hypanthium fleshy, urn-shaped, carpellary vascular supply recurrent; integument ca 8 cells across. - 1/100-150. N. temperate; 1/3 spp. in Europe.
[Potentilleae + Agrimonieae]: ?
Age. The age of this node is ca 62 Ma (Y. Xiang et al. 2016).
2E. Potentilleae Sweet
Herbs, usually perennial, (shrubs); (epicalyx +); receptacle enlarged; (anthers [?pseudo]unithecal); style subapical to gynobasic; integument ca 4 cells across. Potentillineae: (A 1), (extrorse); style often lateral/gynobasic. 5-6/540: Potentilla + Argentina et al. N. temperate to Arctic (montane tropics to S. temperate). [Fragariinae + Alchemillinae]: anther thecae more or less confluent; parietal tissue ca 2 cells across, nucellar cap ca 7 cells across. Fragariinae Torrey & A. Gray: (leaves simple); (G 1); phragmidiaceous rusts 0 (Fragaria +).
Fragariinae: 10/60. Alchemillinae 3/960-1100: Alchemilla (1000+). N. temperate, esp. Europe, tropical mountains (S. temperate).
Age. Crown-group Potentilleae are aged at 50-25 Ma (Gehrke et al. 2015) or (52.4-)44.9(-36.1) Ma (Feng et al. 2017).
Synonymy: Alchemillaceae Martinov, Potentillaceae Berchtold & J. Presl, Tormentillaceae Martynov
2F. Agrimonieae Lamarck & de Candolle
Pollen colpi operculate, surface striate or microverrucate; G 1-5; integument 6-8 cells across; phragmidiaceous rusts 0.
Agrimoniinae J. Presl - 5/20: Agrimonia (15). N. Temperate, Africa; Sanguisorbineae Torrey & A. Gray - 7/360: Cliffortia (115), Acaena (100). ± Worldwide, few Indo-Malesia or tropical America.
Synonymy: Agrimoniaceae Gray, Fragariaceae Nestler, Poteriaceae Rafinesque, Sanguisorbaceae Berchtold & J. Presl
3. Amygdaloideae Arnott
Plant woody, (ectomycorrhizal); sugar alcohol sorbitol [carbohydrate transport], cyanogenic glycosides, flavones +, ellagic acid 0; cuticle waxes as tubules or platelets; leaves simple (compound); G <5, opposite petals or sepals, 2 ovules/carpel, papillate funicular obturator +, stigma usu. wet; fruit a follicle.
57/1,540. Mostly North Temperate..
Age. Crown-group Amygdaloideae are (91-)90.2(-89.4) Ma (S.-D. Zhang et al. 2017) or (91.8-)87.0(-82.8) Ma (Chin et al. 2014), a similar age is suggested by Töpel et al. (2012), and, somewhere around about this node, ages of (51-)47-46(-42) Ma (Wikström et al. 2001) or (59-)44, 40(-27) Ma (Bell et al. 2010) have been suggested.
3A. Niellieae Maximowicz
Cyanogenic glycosides?; leaf teeth colleter-like; pollen surface smooth, perforate, orbicules +; ovule apical, apotropous (-5, pleurotropous); seeds hard, shiny; endosperm copious; n = 9.
2/24: Niellia (14). E. and W. North America, northeast Asia.
Synonymy: Neilliaceae Miquel
[Spiraeeae [Lyonothamneae + Amygdaleae]] [[Sorbarieae [Osmaronieae + Kerrieae]] [Gillenieae + Maleae]]]: ?
3B. Spiraeeae Candolle
Vestured pits +; nodes 1:1 [?all]; stipules 0; pollen surface striate, perforate, orbicules +/0; ovules 6-8/carpel, unitegmic; (fruit an achene - Holodiscus).
8/106: Spiraea (80-100). N. temperate, to Columbia, (S. and) E. Africa, West Malesia.
Age. The age of this clade is estimated to be around (62.9-)59.2(-56.0) Ma (Chin et al. 2014).
Synonymy: Spiraeaceae Bertuch
[[Lyonothamneae + Amygdaleae] [[Sorbarieae [Osmaronieae + Kerrieae]] [Gillenieae + Maleae]]]: ovules 2/carpel, collateral.
Age. Crown-group Prunus + The Rest are dated to 36.1-34.3 Ma (Naumann et al. (2013: too young), (72.4-)67.8(-63.7) Ma (Chin et al. 2014) and about 49.6 Ma (Hohmann et al. 2015).
[Lyonothamneae + Amygdaleae]: ?
3C. Lyonothamneae A. Gray
Cyanogenic glycosides 0; leaves opposite, compound, stipules deciduous; G seminferior, placentation apical; ovules 4-6/carpel.
1/1: Lyonothamnus floribundus. California Islands (off S. California).
3D. Amygdaleae Jussieu
Tree to shrub, (deciduous); (ectomycorrhizal); cork superficial; true tracheids 0; lamina vernation laterally or vertically conduplicate, extrafloral nectaries +, on petiole/lamina margin towards base/abaxial surface, leaf teeth colleter-like; (plant dioecious); inflorescence racemose/corymbose/flowers single, from axil of ?prophyll; (K, C, similar, ± sepal-like); G 1, stigma bilobed; outer integument 6-8 cells across, inner integument 3-6 cells across, nucellar cap 2-3 cells across, (integument 1, ca 12 cells across), parietal tissue ca 8 cells across, obturator from ovary wall; fruit a drupelet, (stones 2), (outer pericarp [= hull] dry, dehiscent), endocarp and inner mesocarp lignified; seed coat mostly pachychalazal; n = 8(-8x), nuclear genome [1C] 0.28-3.65 pg.
1 [Prunus]/ca 275. Temperate and tropical montane.
Age. The beginning of diversification within Prunus has been dated to (67.4-)62.4, 60.7(-55) Ma (Chin et al. 2014), the species sampled by Y. Xiang et al. (2016) started diverging ca 30 Ma, while L. Zhao et al. (2016c: p. 17) dated "the first formation of the racemose group", basal, paraphyletic) at (66.3-)55.4(-45.1) Ma.
There are well-preserved ca 49.5 Ma fossil flowers of Prunus from Washington State (Benedict et al. 2011).
Synonymy: Amygdalaceae Marquand, Prunaceae Martinov
[[Sorbarieae [Osmaronieae + Kerrieae]] [Gillenieae + Maleae]]: ?
Age. The age of this split is ca 92 Ma (Y. Xiang et al. 2016).
[Sorbarieae [Osmaronieae + Kerrieae]]: ?
3E. Sorbarieae Rydberg
Petiole bundle deeply U-shaped (with wing bundles)/± annular/bundles 3, arcuate; leaves compound (simple: Adenostoma); pollen surface striate, otherwise perforate, microechinate, etc., orbicules +; (G 1, Adenostoma), placentation apical; (fruit an achene: Adenostoma).
4/8: Sorbaria (4). Central to East Asia, W. North America
[Osmaronieae + Kerrieae] / Kerriodae D. Potter, S. H. Oh, & K. R. Robertson: phragmidiaceous rusts 0; non-cyanogenic nitrile glucosides +.
3F. Osmaronieae Rydberg
Cork superficial; pith chambered; stipules deciduous; styles lateral; obturator from ovary wall; fruit a drupe, or septicidal capsule, the carpels also opening adaxially [Exochorda]; seed coat vascularized [Exochorda, Oemleria]; n = 8.
3/9: also Prinsepia. Central to East Asia, W. North America.
Age. Well-preserved fossil flowers of Osmaronia from ca 49.5 Ma are known frrom northeastern Washington State, U.S.A. (Benedict et al. 2011).
3G. Kerrieae Focke
Wart-like projections on lamina; G 1-5; ovule ?obturator; fruit an aggregate, nut-like units, (achenes: Neviusia); n = ?
4/4. East Asia, W. North America, Alabama.
Synonymy: Coleogynaceae J. Agardh, Rhodotypaceae J. Agardh
[Gillenieae + Maleae] / Pyrodeae C. S. Campbell, R. C. Evans, D. R. Morgan, & T. A. Dickinson
Flavone C-glycosides +; cork superficial [?Gillenia]; rays often narrow; colleters + [probably elsewhere]; G ± connate, adnate to base of hypanthium, opposite K or odd member abaxial, gynoecial ring primordium +; ovules two/carpel, ± apotropous, (micropyle bistomal), funicular obturator +; exotesta ± thickened, often mucilaginous, mesotesta thick, sclerotic; Gymnosporangium rust common.
Age. The split of the two tribes below can be dated to (67.1-)60.6(-55) Ma (Chin et al. 2014) or ca 54 Ma (Y. Xiang et al. 2016; see also S.-D.Zhang et al. 2017).
3H. Gillenieae Maximowicz
1/2. E. North America.
N = 17; four copies of GBSSI gene.
33/1,010. Northern Hemisphere, few S. South America; ± temperate.
Age. The crown-group age is (54.4-)50.1(-49.4) Ma (S.-D. Zhang et al. 2017).
3I. Lindleyinae Reveal
(Plant dioecious); 4-many pleurotropous ovules/carpel; (ovules with with chalazal projection - Kageneckia); Gymnosporangium rust 0.
2/5. Mexico, Peru, Chile. [Kageneckia Flower, Fruit.]
Synonymy: Lindleyaceae J. Agardh
Vauquelinia + Malinae]: ?
Age. Stem-group Malinae are (64-)58, 53(-43) Myo (Lo & Donoghue 2012).
3J. Vauquelinia Bonpland
Tannin-containing cells pervasive; fruit septicidal, carpels opening adaxially (and partially abaxially as well); ovules with chalazal projection; n = 15.
1/3. S.W. North America.
3K. Malinae Reveal
(Plant ectomycorrhizal); (phloem stratified [± sclereidal] - Malus); crystals in axial parenchyma; (leaves compound), stipules deciduous; G at least half inferior, (carpels laterally free); outer integument 5-14 cells across, inner integument 3-6 cells across, nucellar cap ca 4 cells across; hypanthium fleshy in fruit [= "pome"], (endocarp +), nuclear genome [1C] 1.35-2.25 pg.
28(-45 - Rushforth 2018)/1,000: Crataegus (260, inc. Mespilus), Cotoneaster (260), Aria (97), Sorbus (92), Pyrus (73), Photinia (65), Malus (47) - see Robertson et al. (1991). Largely north Temperate.[Photo - Flower]
Synonymy: Cydoniaceae Schnizlein, Malaceae Small, nom. cons., Mespilaceae Schultz-Schultzenstein, Pyraceae Vest, Sorbaceae Brenner
Floral formula: * ⚥ K 5; C 5; A (10-)15<; N; G (1-)10< / [3-5].
Evolution: Divergence & Distribution. See S.-D. Zhang et al. (2017) for additional ages for tribes and groups of tribes, and Dobeš and Paule (2010), Gehrke et al. (2015) and Feng et al. (2017) for some ages within Rosoideae. Prunus endocarps have been found in the early Eocene of China ca 55 Ma, and there was considerable diversification of the family in the Eocene (Wehr & Hopkins 1994; DeVore & Pigg 2007; Benedict et al. 2011; Q.-Y. Li et al. 2011 and references).
Töpel et al. (2012) looked at diversification in a clade of North American Potentilla s.l. (Rosoideae) in the context of changing climate since the late Oligocene ca 23 Ma. Nearly all the >120 species of the shrubby Cliffortia (Agrimonieae) are to be found in the Cape Floristic Region of South Africa (Linder 2003).
All but two of the tribes of Amygdaloideae diverged between 96-88 Ma, and then nothing much seems to have happened for the next over 20 Ma, and in Amygdaleae, nothing for almost 60 Ma (Y. Xiang et al. 2016). The inferior-ovaried Malinae may represent a rapid but ancient radiation (Campbell et al. 2007; c.f. in part Xiang et al. 2016) perhaps associated with a whole genome duplication in the stem lineage (there was another in the stem lineage of Maleae) and also with the climatic changes that occurred at the end of the Palaeocene to the beginning of the Oligocene (Xiang et al. 2016). Lo and Donoghue (2012) dated stem group Malinae to late Palaeocene, with subsequent divergence in the Eocene and Oligocene, a substantial amount of movement around the northern hemisphere, probably via the Beringian land bridge, and much heterogeneity in clade size that is independent of age. Aldasoro et al. (2005) also suggest biogeographic relationships in this group. Rosa minutiflora, from Baja California and the Asian R. berberifolia diverged ca 24.3 Ma (Fougère-Danezan et al. 2015).
Hybriidization, polyploidy and apomixis are common in Rosaceae (see also below). For the relationship between polyploidy and diversification - perhaps direct - see Vamosi and Dickinson (2006). Here, as elsewhere in angiosperms, this relationship is probably not because speciation is faster in polyploids (the reverse may be more likely), rather, it is more likely to be the result of a ratchet mechanism since polyploidy is irreversible (Scarpino et al. 2014). Within Fragaria itself, the only taxon known to have one of the parental genomes of the South American F. magellanica grows in eastern Japan (Rousseau-Gueutin et al. 2009). Within Crataegus clades are linked with geography, but parents of genomes may have very disparate geographic origins (Lo et al. 2009). Full-sized trees are restricted to Amygdaleae and Maleae where they are associated with the acquisition of fleshy disseminules (Xiang et al. 2016). There may a connection between genome duplication, habit, disseminule type and diversity (Xiang et al. 2016), but as these authors noted, although Rosoideae have fleshy fruits and are even more speciose than Maleae, they are mostly herbs to shrubs and there is not the same association with genome duplications.
There are about 34 species of Lachemilla (= Alchemilla, Potentilleae), herbs of various kinds to small shrubs, and they grow in the páramo of South America, the group being a very important component of the vegetation there (Gehrke et al. 2008; Sklenár et al. 2011; Morales-Briones et al. 2018a). The shrubby habit has evolved (and been lost) in Alchemilla growing in alpine regions on African mountains (Gehrke et al. 2015).
Koski and Ashman (2016a, b) have carried out extensive studies on floral UV absorbtion patterning in Potentilla s.l. and also flower size, linking variation in the former to environmental factors (high UV, petals "black", UV absorbtion), and variation in the latter to reproductive character displacement.
Optimisation of characters on the tree presents problems. Potter et al. (2007) used DELTRAN, and so being host to Gymnosporangium rusts is not an apomorphy of Pyrodeae; using ACCTRAN (as here) it is. They divided up the presence of sorbitol (see e.g. Waalart 1980; Rennie & Turgeon 2009) into two states; it might be present in only small amounts (Dryadoideae), or it was more abundant (Amygdaloideae); presence of at least some sorbitol could be used to characterize the larger clade. However, given the relationships suggested by Y. Xiang et al. (2016) and followed here, I have placed the aquisition of sorbitol as features of both subfamilies, but both it, and the presence of cyanogenic glucosides, could characterize the family and be lost in Rosoideae.
Ecology & Physiology. Some, but not all, Dryadoideae, are N-fixers, but the widespread Dryas integrifolia appears to be unable to fix nitrogen (Markham 2009). Nodules and association with Frankia have also been reported from other Rosaceae, e.g. from Rubus ellipticus (Markham 2009). Species of the N-fixing Cowania (Dryadoideae) and the non N-fixing Fallugia (Rosoideae-Colurieae) can be successfully intergrafted; when Fallugia is the stock the combination will not fix nitrogen (Kyle et al. 1986).
Dryas is ectomycorrhizal and is one of the eight major biomass accumulators in tundra vegetation. Four other species of these eight are also ectomycorrhizal, and the apparently endomycorrhizal Rubus is also on this list (Chapin & Körner 1995; Gardes & Dahlberg 1996). For literature on mycorrhizae, see Brundrett (2017a) and for their ages, etc., see Tedersoo and Brundrett (2017) and Tedersoo (2017b).
Potentilla arguta has glandular hairs and may be protocarnivorous, being able to digest proteins (?source of enzymes) and take up at least some of the products (Spomer 1999); the ability of plants with such hairs to digest at least some proteins is quite widespread in flowering plants.
Rubus in particular is an effective invader of natural areas (Daehler 1997).
Pollination Biology & Seed Dispersal. There is a period of about 19 days between pollination and fertilization in Prunus persica (Herrera & Arbeloa 1989).
For apomixis, common in Rosaceae, see below.
Y. Xiang et al. (2016) discuss the evolution of fruit type in the family in some detail (see above).
Plant-Animal Interactions. Galls caused by cecidomyid midges are quite common in North American Rosaceae (Gagné 1989). Cynipid gall wasps of the tribe Diplolepidini are notably common on Rosa, Diplolepis rosae forming the well-known robin's pincushion or bedeguar gall (Csoka et al. 2005; Redfern 2011).
Caterpillars of a variety of groups of ditrysian Yponomeutoidea moths are recorded as eating Rosaceae (Sohn et al. 2013).
There are prominent basal nectary glands on the lamina of fossils identified as Prunus from the Okanogan Highlands formation of western North America ca 49.5 Ma (DeVore & Pigg 2007; Benedict et al. 2011), apparently the earliest example of foliar extrafloral nectaries.
For literature on the evolution of the dipteran tephritid Rhagoletis as it moved from Crataegus to introduced Malus, see Forbes et al. (2017).
Bacterial/Fungal Associations. At least some Dryadoideae and Amygdaloideae are ectomycorrhizal (ECM) plants. 154 ECM OTUs have been recorded from Dryas integrifolia alone in a Low to High Arctic transect, many of these also being widely distributed outside the Arctic (Gardes & Dahlberg 1996; Timling & Taylor 2012), however, Bjorbækmo et al. (2010) found considerable geographical partitioning in the ECM fungi of D. octopetala. In southern Oregon Geopora sp. (Pezizales, a hypogeous ascomycete) forms ECM associations with Cercocarpus ledifolia (Amygdaloideae) in particular, and other generalist ECM species from the same habitat associated with C. ledifolia also form associations with Quercus garryana (Fagaceae) and Arctostaphylos spp. (Ericaceae) (McDonald et al. 2010), the result being a complex mycorrhizal network. Ascomycetes are also associated with other ECM Rosaceae, including Purshia (McDonald et al. 2010). Rose (1980) recorded vesicular-arbuscular mycorrhizae on Purshia and Cercocarpus.
Savile (1979b; see also Jackson 2004b: possible codivergence) discusses the distribution of phragmidiaceous rusts within Rosaceae-Rosoideae; they are found on no other Rosaceae, and only rarely on plants from other families. Most of these rusts are autoecious, that is, their entire life cycle occurs on the one species. Gymnosporangium rusts, found scattered on Amygdaloideae-Pyrodeae, are heteroecious. Here the telial stage (the teliospore is a thick-walled resting spore that germinates to produce basidiospores) is common on some Cupressaceae, the aecial stage, which produces thinner-walled binucleate aeciospores, is found on Pyrodeae (Lo & Donoghue 2012 for "gains" and "losses" of infestation). Fruits of Amygdaloideae can be seriously damaged by Monilinia (polyphyletic - ascomycete-Sclerotiniaceae), also found on Ericaceae (Holst-Jensen et al. 1997). Interestingly, Rosaceae rarely produce phytoalexins, protective compounds induced by e.g. fungal infection (Harborne 1999).
Vegetative Variation. Chin et al. (2013) surveyed nectaries and nectary-like structures on the leaves of Prunus and optimized them on a phylogenetic tree. Interestingly, leaf teeth in several species of the genus, as well as in Niellia and Physocarpus, are colleter-like both in terms of their structure and what they secrete (mucilage); other species of Amygdaloideae, at least, should be surveyed for such teeth.
Genes & Genomes. The basic chromosome number of the family may be x = 7 (Shulaev et al. 2010) or x = 9 (Murat et al. 2015b), with subsequent rearrangements. See Kajewski (1957) for classic cytological work on Geum.
It has long been suspected that Pyreae were of wide hybrid origin, as their chromosome number might imply (n = 9 [Rosoideae] x n = 7 [Spiraeaoideae] → n = 16 [some Maloideae]) (Evans et al. 1998). However, Evans and Campbell (2002) suggest that polyploidisation with subsequent aneuploidy (9 x 2 → 18, 18 - 1 → 17) within the diploid Gillenia clade (herbaceous, with compound leaves) or something similar is more likely. Gillenia is sister to Pyreae (Potter et al. 2002; Evans & Dickinson 2002) and is host to the same rusts that are found on other Pyrodeae, but it has only two copies of the GBSSI gene, as in the rest of the family; other Pyrodeae have four copies of this gene. Genome sizes in Rosaceae as a whole are rather low, although in Pyreae they are rather higher (Dickson et al. 1992). There may have been a genome duplication in Malus and Pyrus somewhere around (21.3-)19.9, 18.3(-16.4) Ma, yet the oldest fossils assigned to these genera are about 2½ times as old (Vanneste et al. 20104a) while Landis et al. (2018) date the MADOα event involving all three clades in J. Sun et al. (2018: see below) to ca 9.4 Ma; Lachemilla and immediately related genera may also share a genome duplication (Morales-Briones et al. 2018b), and a duplication in Rosoideae-Colurieae on up (see above, the ROPAα event, has been dated at 60.2 Ma (Landis et al. 2018).
Hybridization and polyploidy are common in Rosaceae, and there is "intergeneric" hybridization in Rosoideae (e.g. Smedmark et al. 2003; Töpel et al. 2011). Allopolyploidy in Fragariinae and its taxonomic implications were studied by Lundberg et al. (2009). Within Fragaria itself, the only taxon known to have one of the parental genomes of the South American F. magellanica grows in eastern Japan (Rousseau-Gueutin et al. 2009). Deep hybridization within Prunus has been invoked to explain contrasting phylogenies obtained when using nuclear and plastid data, and it also fits with chromosome numbers (Chin et al. 2014), and from the analysis of L. Zhao et al. (2016c) there appear to be four hybrid clades/subgenera at the base of the tree that are allopolyploids (and have racemose inflorescences). Further complicating the issue of hybridization is the frequency of apomixis, the two often being associated.
Indeed, apomixis, unequal partitioning of the chromosomes at meiosis, and hybridization, are common here, as in taxa like Rubus (e.g. Sochor et al. 2015), Potentilla and Alchemilla (e.g. Dobeš et al. 2015), all Rosoideae, and Amelanchia, Sorbus, Cotoneaster and Crataegus, all Amygdaloideae-Pyrodeae (Dickinson et al. 2007; see also Asker & Jerling 1992; Hörandl et al. 2007; Talent & Dickinson 2007; Coughlan et al. 2017; Majeský et al. 2017; Dickison 2018 and other papers in Taxon 67(6)). In Crataegus the hybrids have various ploidy levels (there are also autotriploids). There were ca 17 North American species of Crataegus in 1896, while 30 years later there were over 1000 species, and at least some are triploid apomictic hybrids; C. S. Sargent described over 700 of these ("I know Crataegus is in a mess - I put it there" - ?apocryphal). In general, the evolution of apomixis seems to have preceded hybridisation (Dickinson et al. 2007). In pentaploid Rosa unequal division occurs at meoisis, and as a result megaspores have 4/5th of the genome and microspores 1/5th (Wissemann & Ritz 2007 and references). There are ca 755 species of European brambles, of which 6 are diploid (two of these may be extinct), although there are four more diploids in surrounding areas, as well as others in North America, etc. (Sochor et al. 2015). In Europe crosses between sexual (series Glandulosi: female) and apomictic (Discolores: pollen) species generate novel apomicts (series Radula: Sarbanová et al. 2017). In Amelanchier the diploid taxa behave as species according to several definitions of the term, however, polyploid apomicts break down the relative simplicity of the variation patterns at the diploid level (Burgess et al. 2015).
For sex chromosomes in North American octoploid Fragaria, see Tennessen et al. (2018). Here a sex-determining region, a gene cassette, is found in female individuals alone - but on different chromosomes in different taxa. This the result of sequential translocations of the one casette, which picks up some of sequences from the adjacent part of the host chromosome each time it moves (Tennessen et al. 2018).
Economic Importance. The codling moth, the tortricid Cydia pomonella and relatives, are major pests of apples and their relatives.
Chemistry, Morphology, etc. For general chemistry, see Hegnauer (1973, 1990), and for 2-pyrone-4,6dicarboxylic acid distribution, see Wilkes and Glasl (2001). Okuda et al. (1992) discuss tannin distribution in the family; chlorogenic acid was found in nearly all taxa examined. For cyanogenesis, see also Thodberg et al. (2018); non-cyanogenic glucosides are apparently restricted to Kerriodae (Lechtenberg et al. 1996).
A polyderm is common, although perhaps not in Pyreae (Mylius 1913); Evert (1963) notes a distinctive stratified phloem in Malus. 1:1 nodes occur in Spiraea, which also lacks stipules, although normally Rosaceae have stipulate leaves and 3:3 nodes (see e.g. Sinnott & Bailey 1914). There are extensive data on cuticle waxes in the family (Fehrenbach & Barthlott 1988), but they are recorded only as summaries in the context of conventional subfamilies; Barthlott (pers. comm.) kindly provided a more detailed breakdown.
The epicalyx in some Rosaceae seems to represent stipules associated with the calyx members. For hypanthium development, see Rauh and Reznik (1951). Ronse de Craene (2007) wondered whether the petals were modified staminodes. There are often five traces to each carpel. Rosa setigera is reported to have a synstigma like that of Ficus (Teixeira et al. 2018), but a synstigma involve stigmas of different flowers - here the styles are free and no fusion of the stigmas of the two whorls of separate carpels is mentioned, although they are close to each other (Kemp et al. 1993), so even the existence of an extragynoecial compitum is unclear. Even in taxa with inferior ovaries, there is great variation in whether or not the carpels are connate, or what parts are connate, and in whether or not the carpels are adnate to the axial tissue enveloping the carpels/hypanthium. Thus Cotoneaster has an inferior ovary in which the carpels are more or less separate from each other although adnate to the hypanthium, c.f. also Pyracantha. The odd genus Dichotomanthes, also included in Pyreae, has a single carpel that is superior in position (Rohrer et al. 1994); this must represent a reversal. In general, the styles of the separate carpels are somewhat off-centre, and a gynobasic style is but an extreme form of this asymmetry. The single, basal ovule of Chamaebatia (Dryadoideae) lacks an obturator (Evans & Dickinson 2002), while ovules of Rhodotypos have a protruding nucellus (c.f. Rhamnaceae). Prunus may have one or two integuments, in the latter case, these may be free only above the micropyle (Lora et al. 2015). The lignified exotesta common in the family can be found even in the seeds of the drupaceous Prunus.
Some general information is taken from Decaisne (1874), Robertson (1974), Hess and Henrickson (1987: Vauquelinia), Kalkman (2004), Judd et al. (2002), and especially Potter et al. (2007). There is information on cork initiation and bark anatomy in Lotova and Timonin (e.g. 1998, 1999, 2002) and Weiss (1890), on wood anatomy in S.-Y. Zhang (1992), on petiole vasculature in Morvillez (1917) and Song and Hong (2018: the "nodes" mentioned are not nodes), on inflorescence morphology and development in Weberling (1989) and Bull-Hereñu and Claßen-Bockhoff (2011b), and on floral morphology in Kania (1973) and Evans and Dickinson (1999a, 1999b, 2005); androecial diversity is discussed in Murbeck (1941: also vasculature, Neurada etc. "basal") and Lindenhofer and Weber (2000 and references), pollen morphology in Chung et al. (2010: Sanguisorbeae [= Agrimonieae], Song et al. (2016: Sorbarieae, 2017a: Neillieae, 2017 b: Spiraeeae), carpel orientation and general morphology in Focke (1888), Schäppi (1951: peltate and plicate carpels), Schäppi and Steindl (1950), Sterling (1966, 1969 and references), van Heel (1981, 1983: development), and Smedmark and Eriksson (2006: stylar hook), ovule morphology in Péchoutre (1902: quite comprehensive, also seeds), Juel (1918: see comments on Péchoutre; orientation of carpels) and Schäppi and Steindl (1950: Rosoideae), and exotesta in Frohne and Jensen (1992).
Phylogeny. Initially Rosoideae and a number of clades within it, Amygdaloideae, Amygdaloideae minus Lyonothamnus, [Pyrodeae + Sorbarieae] and Pyrodeae were all well-supported, but little could be said of other larger patterns of relationship (e.g. Morgan et al. 1994; Potter et al. 2002; Potter 2003; Potter et al. 2007a). The position of Dryadoideae was uncertain, other than being a rather basal branch in the tree (Potter et al. 2002: Evans et al. 2002), hence perhaps its lack of obturators. Potter (2003: several genes) found that Dryadoideae were fairly well supported as sister to other Rosaceae, but their position was not secure in Potter et al. (2007a), although a sister group relationship with Spiraeaoideae (= Amgydaloideae) was perhaps most likely (see also Töpel et al. 2012; Z.-D. Chen et al. 2016). However, Chin et al. (2014), H.-L. Li et al. (2015, 2016), M. Sun et al. (2016) and S.-D. Zhang et al. (2017: analysis of whole chloroplast genomes, position not stable) all suggested that Dryadoideae and Rosoideae formed a clade, and this suggestion is followed above. However, Y. Xiang et al. (2016) found that Dryadoideae were sister to the rest of the family, and they thought that other positions were unlikely.
Within Dryadoideae, Dryas is sister to the rest of the subfamily (e.g. H.-L. Li et al. 2015; M. Sun et al. 2016; S.-D. Zhang et al. 2017).
Eriksson et al. (2003) provide a phylogeny of Rosoideae; see also Y. Xiang et al. (2016) and S.-D. Zhang et al. (2017) for a phylogeny of the subfamily; the relationships of the tribes above may vary, thus Zhang et al. (2017) suggest the grouping [Ulmarieae [Colurieae [Rubeae [Agrimonieae [Roseae + Potentilleae]]]]], however, Filipendula (Ulmarieae) is generally found to be sister to other Rosoideae. Rubeae: The current infrageneric classification of Rubus does not reflect relationships there (Alice & Campbell 1999) and it is paraphyletic in Z.-D. Chen et al. (2016: weak support). Agrimonieae: For relationships, see S.-D. Zhang et al. (2017). Roseae: For Rosa, see Bruneau et al. (2007), Wissemann and Cox (2007) and Koopman et al. (2008); relationships here are not easy to disentangle. There is still rather little support in the quite comprehensive analysis of Fougère-Danezan et al. (2015), again, hybridization complicates the issue; see also M. Sun et al. (2016). Potentilleae: Alchemilla, Fragaria, and other genera form a well-supported clade outside Potentilla and relatives (see also Dobeš & Paule 2010). Potentilla (including a few segregate genera) is sister to a small clade including Argentina (= Potentilla sect. Anserina), the two forming a clade sister to the other Potentilleae (all relationships with strong support: Dobeš & Paule 2010; see also Eriksson et al. 2003). Eriksson et al. (2015) and Feng et al. (2017) noted the polyphyly (five or more separate clades!) of the small genus Sibbaldia while Töpel et al. (2011) and Koski and Ashman (2016a) discussed relationships within Potentilla s.l. - Fragariinae are sister to Alchemillinae. For relationships within Alchemilla s.l., which have a strong geographic signal, see Gehrke et al. (2008). Andean Lachemilla, often placed in Alchemilla, includes some 61 species all told, and there has been extensive hybridization, one clade, which includes species with orbiculate leaves, probably being of hybrid origin (Morales-Briones et al. 2018a, b).
Within Amygdaloideae, Exochorda forms a small clade along with Oemleria and Prinsepia (Evans & Dickinson 1999a for information); they have been placed near Prunus (Potter et al. 2002, see also Lee & Wen 2001) to which they do show some morphological similarity; Lyonothamnus, Niellieae, and Amygdaleae were basal in the subfamily. Although the coverage of genera in Amygdaloideae was quite extensive in Töpel et al. (2012), the sequence of clades differed, Niellieae and Amygdaleae in particular moving higher into the tree, while S.-D. Zhang et al. (2017) preferred the relationships [Lyonothamneae [Niellieae [[Exochordeae + Kerrieae] [Amygdaleae [Sorbarieae [Spiraeeae [Gillenieae + Maleae]]]]]]; see also Chin et al. (2014), H.-L. Li (2015), M. Sun et al. (2016) and Z.-D. Chen et al. (2016: relationships again rather different from those above) for phylogenies. Y. Xiang et al. (2016) found the relationships above which for the most part were well supported. Spiraeeae in particular had moved basally in the tree, which is rather less pectinate than earlier suggestions, and the position of the tribe is also not stable in the analysis of S.-D. Zhang et al. (2017); S.-X. Yu discused relationships within Spiraea, and they found previously-recognized infrageneric taxa to be unsupported.
Amygdaleae. For phylogenies of Prunus s. l., see Lee and Wen (2001), Bortiri et al. 2001 (ITS and trnL-trnF together produced some structure), Wen et al. (2008: some conflict between ITS and ndhF), Chin et al. (2013), Yazbek and Oh (2013: subgenus Amygdalus), and L. Zhao et al. (2018: Malesian section Mesopygeum). Shi et al. (2013) had fairly good sampling, some 84 species, concatenated data, and recovered three major clades (subgenera), Chin et al. (2014) recovered two main clades, one with racemose inflorescences, while the analyses of L. Zhao et al. (2016c) suggested that there were four clades of hybridogenous origin at the base of the tree that had racemose inflorescences, and species like P. africana were particularly peripatetic. The distribution and nature of calcium oxalate crystals correlate quite well with relationships here (see Lersten & Horner 2000); Maddenia (dioecious, apetalous) is also to be included in Prunus (Potter et al. 2007a). Maleae. Malineae (Pyrinae) include the bulk of the tribe and many taxa that are ornmentals or have edible fruit. Aldasoro et al. (2005) suggest relationships based on an analysis of morphological and anatomical data. Generic limits remain difficult, since there is little molecular divergence between many of them but considerable divergence within them (Dickinson et al. 2007; Q.-Y. Li et al. 2012: little support for most relationships discussed). Recent work including over 330 species and large amounts of data has provided substantial resolution of relationships, although support along the backbone could still be improved (Lo & Donoghue 2012). S.-D. Zhang et al. (2017) found largely similar results with four main groups, but they, too, noted incongruence between their results and those using nuclear markers - hybridization.... Relationships immediately outside the inferior-ovaried Malinae in J. Sun et al. (2018: 15 chloroplast genes) are the same as those above, inside that group they found three main clades, Crataegus-Amelanchier, Sorbus-Cotoneaster and Malus-Aria, although support generally was weak except for relationships in the first group. Lo et al. (2007, 2009) and Zarrei et al. (2014, 2015) focussed on Crataegus s.l. where hybridization also greatly confuses the issue, F. Li et al. (2014) looked at relationships within Cotoneaster, where nuclear and chloroplast genes tended to suggest different relationships, again perhaps because of past hybridization, while M. Li et al. (2017) examined relationships with Sorbus s. str.. Interestingly, Cotoneaster forms grafts with Crataegus.
Classification. The old Spiraeoideae (= Amygdaloideae; changed iii.2014), characterised by follicular fruits, are strongly paraphyletic, and include both Prunoideae/Amygdaloideae and Maloideae, however, tribes in Spiraeoideae may represent clades (see especially Evans et al. 2002; Potter et al. 2007a). The classification here follows that of Potter et al. (2007a); Prunus is circumscribed broadly.
Generic limits in Malinae may reflect the European origin of taxonomy and the fact that the group is common in Europe (e.g. Walters 1961). However, there is now support for many of the main clades in Malinae and one can perhaps aspire to a stable taxonomy; Sorbus and some other genera have turned out to be polyphyletic (Lo & Donoghue 2012), although it does not make deciding on generic limits any easier (Gehrke in Kadereit et al. 2016), thus Robertson et al. (1991) recognised 28 genera in Maloideae (= Malinae), Rushforth (2018) 45 genera (and counting). Generic limits in Potentilleae are becoming clearer (Dobes & Paule 2010; c.f. Soják 2008 for an alternative); Alchemilla is to include Aphanes and Lachemilla (Gehrke et al. 2008). Shi et al. (2013) produced an infrageneric classification of Prunus, but it does not agree that well with the relationships suggested by L. Zhao et al. (2016c).
Fruit types are certainly not as good indicators of relationships within Rosaceae as was for a long time thought. Thus the old Spiraeoideae used to be considered a very natural group (e.g. Kalkman 1988) characterised by follicular fruits, are strongly paraphyletic, and include both Prunoideae/Amygdaloideae and Maloideae; Prunoideae were characterized by their drupaceous fruits and Maloideae by their pomes (a pretty useless term). However, chemistry, chromosomes, and fungi all support the realignments suggested by molecular data (especially Morgan et al. 1994), as does developmental work by Evans and Dickinson (1999a, b, 2002).
Previous Relationships. Rosaceae as circumscribed above are holding together very well despite their morphological heterogeneity, but there have been departures. Chrysobalanaceae, often associated with Rosaceae in the past, are well embedded within Malpighiales, Quillaja rather unexpectedly is an isolated clade within Fabales, while the poorly-known Guamatela is correspondingly isolated in Crossosomatales (Oh & Potter 2006).
Botanical Trivia. Trees of Polylepis tarapacana grow at some 5,100 m in Bolivia, the highest altitude for any tree (Hoch & Körner 2005).
[[Rhamnaceae [Elaeagnaceae [Barbeyaceae + Dirachmaceae]]] [Ulmaceae [Cannabaceae [Moraceae + Urticaceae]]]]: styles branched; ovules apotropous, trans-spliced intron in nad1 gene [cis-spicing elsewhere].
Age. The age for this node is some (70-)67, 65(-62) Ma (Wikström et al. 2001), (86-)76, 73(-65) Ma (Bell et al. 2010), ca 68.4 Ma (Naumann et al. 2013), or ca 78.1 Ma (Tank et al. 2015: Table S2).
Evolution: Genes & Genomes. For nad1 intron splicing, see Qiu et al. (1998).
[Rhamnaceae [Elaeagnaceae [Barbeyaceae + Dirachmaceae]]]: petiole bundle arcuate; stamens = and opposite C/alternate with P; capsule septicidal; ovule basal, parietal tissue 5-6 cells across; coat multiplicative, exotesta palisade, thick-walled; cotyledons large.
Age. Estimates of the age of this node are (67-)64-62(-59) Ma (Wikström et al. 2001), or (81-)71, 69(-60) Ma (Bell et al. 2010).
Evolution: Divergence & Distribution. Note that most of the apomorphies mentioned above are those of the [Dirachmaceae + Rhamnaceae + Elaeagnaceae] clade for the pre vi.2011 version of the site; they must now reverse - or be uncertain - in the poorly-known Barbeyaceae if it is embedded in that group... Dense, curly hairs on the abaxial surface of the leaf blade could be an apomorphy here (Sytsma et al. 2002), but Qiu et al. (1998) put this feature at a higher node. For changes in infratectum morphology on the tree, see also Doyle (2009).
Chemistry, Morphology, etc. The wood anatomy of Dirachmaceae is particularly similar to that of Rhamnaceae (Baas et al. 2001).
A granular layer below the tectum is more or less developed in both Rhamnaceae and Dirachmaceae. The flattened seed with an antiraphal vascular bundle of Dirachmaceae is similar to seeds in Rhamnaceae (Boesewinkel & Bouman 1997); the distribution of testal and tegmic epidermal cells with sinuous anticlinal walls could be interesting.
Phylogeny. Relationships in this group are discussed above.
RHAMNACEAE Jussieu, nom. cons. - Back to Rosales
Shrubs to trees; chelidonic acid +; saponins, biflavonyls, benzylisoquinoline alkaloids +, myricetin, ellagic acid 0; (vessel elements with scalariform perforation plates); libriform fibres +; sieve tubes lacking non-dispersive protein bodies, plastids with starch grains only; lysigenous mucilage cavities +; leaves opposite or spiral, lamina vernation conduplicate(-plicate) or involute, (margins entire), (stipules 0), colleters +; (plant dioecious); flowers small, 4-5(-6)-merous; K (connate), with a longitudinal median ridge adaxially, C cucullate, enfolding A (0); A adnate to base of C; tapetal cells multinucleate; exine infratectum granulate-intermediate, nectary as disc on ovary, revolute and annular or undistinguished on hypanthium; G [2-3(-5)], opposite K or odd member adaxial, style + or styles separate, with canals as many as carpels (one; 0), stigma papillate; ovules (2/carpel), (median), (apotropous), exostomal (bistomal), outer integument 4-10 cells across, inner integument 3-4 cells across, nucellus conical, parietal tissue 4-7 cells across, nucellar cap to 6 cells across, nucellus ± protruding through micropyle, hypostase +, funicular obturator +; often several megaspore mother cells, (embryo sac bisporic, 8-nucleate - Allium type), antipodals degenerate; fruit with raised annular rim at base [= deciduous hypanthium]; seeds often laterally flattened, (arillate); testa with median integumentary antiraphe bundle +/0, (mesotesta with a few sclerotic cells), endotegmen of cuboid cells, with scalariform thickenings (slightly lignified); endosperm +, (starchy), (perisperm +?), polyembryony common, embryo chlorophyllous.
52 [list: to tribes]/1055 - three main groups below. World-wide, especially tropics and warm temperate regions (map: see van Steenis & van Balgooy 1966; Meusel et al. 1978; Frankenberg & Klaus 1980; Richardson et al. 2003; Australia's Virtual Herbarium xii.2012; Trop. Afr. Fl. Pl. Ecol. Distr. 5. 2010: C. Asia?). [Photo - Flower, Dry fruit, Fleshy fruit.]
Age. Bell et al. (2010) estimated crown Rhamnaceae to be (73-)62, 59(-46) Ma, Richardson et al. (2004), 49.5-43.6 Ma, while at (100.6-)92.6, 91.4(-84.1) Ma the age in Onstein et al. (2015) is more compatible with the fossil record.
Fossils from the Cretaceous-Cenomanian, some 94 Ma, have been identified as Rhamnaceae (Crepet et al. 2004 for references). Calvillo-Canadell and Cevallos-Ferriz (2007) placed Mexican fossils from the late Campanian (ca 73 My) onwards in Rhamnaceae; those from the late Campanian itself have tiny spathulate petals ca 0.7 mm long. Apparent rhamnaceous fossils with puzzling fruits and leaves from the Cretaceous-Maastrichtian of Colombia that are dated to some 68 Ma are also in serious conflict with dates of diversification within the family if assigned to tribes, but not if they are placed incertae sedis in the family (Correa et al. 2010). Fossils assigned to Paliurus are known from ca 66 Ma deposits in the Deccan Traps (Manchester & Kapgate 2014); see also Friis et al. (2011) and Jud et al. (2017) for early fossils.
1. Rhamnoideae Eaton
Ovary inferior; fruit indehiscent; nuclear genome [1C] ca 1.33 pg.
Tropical, north temperate.
1. Ventilagineae Bentham & J. D. Hooker
Lianes, ± twining; leaves 2-ranked; inflorescence fasciculate to cymose; G , semi-inferior; fruits (?dehiscent), ± winged, wing apical; endosperm 0; n = 12.
2/51: Ventilago (40). Esp. Indo Malesia to the Pacific and Australia, 2 spp. Africa and Madagascar (map: see Hauenschild et al. 2018b).
1. Rhamneae Horaninow
(Thorns), (climber); C (0); fruit a drupe; (endosperm 0); n = 6, 10, 12, 13.
15/306: Rhamnus (103), Berchemia (47). World-wide, especially tropics and warm temperate; not southern South America (map: see Hauenschild et al. 2018b).
Age. Crown group Rhamneae are some (31.2-)28.5, 27.6(-24.9) Ma (Richardson et al. 2004), ca 48.5/46.4 Ma (Onstein et al. 2015) or (69.7-)55.6(-40.5) Ma (Y. Yang et al. 2019).
Synonymy: Frangulaceae de Candolle
1. Maesopsideae Engler & Weberbauer
leaves (opposite), lamina strongly glandular-toothed; fruit a drupe, 1-seeded, style lateral; endosperm copious n = 9.
1/1: Maesopsis eminii. Tropical Africa.
[Ampeloziziphoids + Ziziphoideae]: ?
Age. The age of this clade is estimated to be ca 66 Ma (Jud et al. 2017).
Flowers of Notiantha grandensis, from Patagonia and dated to just after the K/P boundary (there are also rhamnaceous leaves in the sediments), have been associated with this node (Jud et al. 2017).
(Lianes); lamina with secondary venation palmate; inflorescence dichasial or fasciculate; (G inferior); fruit a drupe/septicidal capsule [Bathiorhamnus]; n = ?
3/10. Cuba, Brasil, Madagascar (map: see Hauenschild et al. 2018b).
3. Ziziphoideae Luersson
lamina (with secondary venation palmate)); nectary position variable; G semi-inferior to inferior; (embryo sac bisporic, eight celled [Allium type]).
Pantropical, warm temperate.
Age. This clade has been dated to ca 121 Ma (Y.-S. Chen et al. 2017: [Sarcomphalus + Zizyphus]) and (93.2-)89.8(-74.6) Ma (Hauenschild et al. 2018b).
[Pomaderreae + Colletieae]: ?
3. Pomaderreae Endlicher
Plant ectomycorrhizal; hairs stellate; leaves (opposite); flowers (solitary); fruit a ?loculicidal capsule; seeds arillate; n = 12, 18.
12/232: Pomaderris (70), Cryptandra (55), Spyridium (40). Australia: see map in Hauenschild et al. (2018b).
Age. Crown group ages are ca 41 Ma (34.4, 32.3?: Onstein et al. 2015), ca 30 Ma (Zanne et al. 2015: see Tedersoo & Brundrett 2017) and (28.4-)21.8(-16.8) Ma (Hauenschild et al. 2018b).
3. Colletieae Endlicher
Plant thorny, stems green; roots with N-fixing Frankia; serial buds +; leaves opposite, (much reduced), stipules also petiolar [Colletia]; (hypanthium long and tubular); G (superior); fruit (fleshy), (capsular); aril +, often separating from seed; n = 11.
7/22. Most South America, also North America and the Antipodes (map in Hauenschild et al. (2018b).
Age. This clade is some (24.6-)10.3(-8.6) Ma (Hauenschild et al. 2018b).
[Phylicieae [Gouanieae + Paliureae]]: ?
3. Phylicieae Endlicher
Ericoid shrubs; lamina revolute, underside tomentose, (stipules 0 - nearly all Phylicia); inflorescences very variable, inc. capitate/flowers axillary/terminal; fruit a ?loculicidal capsule; seeds arillate; n = ?
4/135: Phylicia (132). Southern and Eastern Africa, especially the Cape of South Africa scattered on islands from St Helena to New Amsetrdam and Réunion (map: see Hauenschild et al. 2018b).
Age. Crown group ages are (41.7-)31.1, 27.5(-22.7) (Onstein et al. 2015), 36.5-10.3 (Onstein et al. 2014), 26.7-19.8 (Richardson et al. 2004: check) or (32-)20.3(-14.7) Ma (Hauenschild et al. 2018b).
Synonymy: Phylicaceae J. Agardh
Ceanothus (53). roots with N-fixing Frankia. North America (map: see Hauenschild et al. (2018b).
Age. Crown group ages range from (34.7-)24.4, 23(-0.3) Ma (Tedersoo & Brundrett 2017; Onstein et al. 2015) to (15.7-)12.5(-12.9) Ma (Hauenschild et al. 2018a).
[Gouanieae + Paliureae]: ?
Age. The age for this node may be around (89.5-)77.8(-70.6) Ma (Hauenschild et al. 2018b).
3. Gouanieae Reichenbach
(Lianes, stem tendrils), (herbs - Crumenaria): G inferior; fruit longitudinally winged, K persistent; fruit loculicidal; n = 11.
Age. Crown-group Gouanieae are (56.3-)46.9(-21.5) Ma (Hauenschild et al. 2018b).
7/75: Gouania (60). Pantropical, some subtropical (map: see Hauenschild et al. 2018b).
Synonymy: Gouaniaceae Rafinesque
3. Paliureae Endlicher
Plant (thorny); ectomycorrhizae +; lamina venation palmate; inflorescence cymose; G (superior); fruit dry/fleshy; (endosperm 0); n = 6, 12, 13, 18, 20...
3/108: Ziziphus (100). ± Pantropical to warm temperate (Europe to East Asia) (map: see Hauenschild et al. 2018b).
Age. Crown-group Paliureae date back to (34.7-)31.6, 30.6(-27.5) Ma (Richardson et al. 2004) or even (82.6-)75.8(-68.4) Ma (Hauenschild et al. 2018b).
Synonymy: Ziziphaceae Adanson
3. Alphitonia Endlicher
4/23: Alphitonia (15). Malesia, Australia (not the S. and S.E.), Pacific Islands to New Caledonia and Hawaii.
Age. The age of Alphitonia s.l. is some (40.8-)29.9(-18.1) Ma (Hauenschild et al. 2018b).
Floral formula: * ⚥ K 5; C 5; A 5 opp. C; N; G  / .
The capsules of Rhamnaceae are rather similar to those of Euphorbiaceae, Phyllanthaceae and Picrodendraceae; in all, there are 1-2 seeds per loculus and the capsule falls to bits as it dehisces. Tthe fruit wall often separates into two layers; the inner layer, woody, twists as dehiscence occurs so helping to eject the seed. However, since the seeds are basal in Rhamnaceae there is no columella as is so typical of these other families, and the latter lack a hypanthium. Phyllanthaceae and Picrodendraceae have two seeds per carpel, Euphorbiaceae have one seed per carpel.
Evolution: Divergence & Distribution. Millan and Crepet (2014) discuss a Solanaceous fossil from the Eocene that they confidently assign to Rhamnaceae. On the other hand, the 99 Ma Rose Creek flower, previously thought to be close to Rhamnaceae, has been described as Dakotanthus cordiformis and with ten stamens is certainly not near Rhamnaceae (Manchester et al. 2018a); see Friis et al. (2011) for other Caenozoic fossils. For more dates, see Hauenschild et al. (2018b).
Richardson et al. (2004, see also Richardson et al. 2001a) discuss the evolution and historical biogeography of the family, noting i.a. the rapid diversification of the speciose Phylica within the last ca 8 My; nearly all the species of Phylicieae as a whole are to be found in the Cape Floristic Region of South Africa (Linder 2003). However, how Phylica gets around is unclear; some 8,000 km separates P. arborea on Gough - midway between South America and the southern tip of Africa - and Amsterdam - midway between Australia and the southern tip of Africa - islands (Richardson et al. 2003). Y.-S. Chen et al. (2017) suggest that Paliurus was on Cretaceous India as it rafted north, being known fossil from all three northern continents in the Caenozoic (Eocene and younger). Hauenschild et al. (2018a, esp. b) looked at the biogeography of Ziziphoideae and suggested that vicariance might be involved in the distribution of some taxa that are now widespread, including Paliureae, Pomaderreae, and Alphitonia s.l., rather than others like Gouanieae and Phylicieae that seemed to have nice Gondwanan distributions, but were young; long distance dispersal was involved in the achieving the ranges of the latter. Alphitonia and relatives probably started in Australia (Hauenschild et al. 2018a).
Ecology & Physiology. There seem to have been three origins of the climbing habit in the family (Richardson et al. 2000a), and in two of these the plants have winged fruits; for twining stem climbers in the faily, see Sousa-Baena et al. (2008b).
Rhamnaceae are quite conspicuous in Mediterranean ecosystems. Onstein et al. (2015) estimate that about 112 species in five groups are found there, Phyliceae in the Cape, Ceanothus in California, Pomaderreae in western Australian, Colletieae in Chile, and Rhamneae in the Mediterranean (Ceanothus is a reseeder - the others?), with another 187 species found in those areas and also elsewhere. Colonization of and diversification in these Mediterranean ecosystems was, they thought, not simultaneous, furthermore, Rhamnaceae were in all these areas well before the onset of the winter rainfall regime, indeed, their diversification rates seem unaffected by the timing of this onset. Thus most diversification within Ceanothus has been within the last ca 6 Ma, before the origin of the Mediterranean-type vegetation the genus now favours, although proto-Mediterranean climates developed in the Californian region ca 15 Ma (Burge et al. 2011; Onstein et al. 2015). In the Cape and Western Australia there seem to have been very low extinction rates, and Phyliceae and Pomaderreae there are xeromorphic, a connection being the nutrient-poor soils in both areas on which the plants grow (Onstein & Linder 2016). For Mediterranean ecosystems in general, see Rundel et al. (2016).
Origins of N-fixing in Rhamnaceae are quite recent compared to those in other families - late Eocene to Oligocene are the dates suggested (H.-L. Li et al. 2015: support for sister-group relationships low).
Pollination Biology & Seed Dispersal. Nectary position is particlarly variable in Colletieae, members of which have a long hypanthial tube, sometimes with a ligule; the nectary can be on the inside of the tube or on the underside of the ligule (Medan & Aagesen 1995; see also Gotelli et al. 2016b for nectaries).
Perhaps a third of the family, all in the Zizyphoideae, has myrmecochorous seeds (Lengyel et al. 2010).
Bacterial/Fungal Associations. The North American Ceanothus has N-fixing actinomycetes, as do many Colletieae; N-fixing genera may form a monophyletic group, although there is no strong evidence for this yet (Richardson et al. 2000b).
Ectomycorrhizae have been reported from Rhamnus and Pomaderris (Malloch et al. 1980; Tedersoo et al. 2008), while Rose (1980) recorded vesicular-arbuscular mycorrhizae on the N-fixing Ceanothus.
For the complex ansmycin maytasinoids found in Colubrina and - the precursors, at least - probably synthesized by a bacterium, see references in Cassady et al. (2004).
Genes & Genomes. cox1 introns are common in Rhamnaceae (Sanchez-Puerta et al. 2008).
Chemistry, Morphology, etc. The lamina of New World species of Gouania has glands at the base while that of Karwinskia has pellucid dots.
Stamens and petals develop from a common primordium, and the petals are initially much smaller than the stamens (Bennek 1958). For pollen tube growth in the hollow styles of Colletieae, which is sometimes through the cells, see Gotelli et al. (2012); hollow styles have been reported elsewhere (Medan 1985: list; Medan & Hilger 1992: Colubrina) and may be an apomorphy for all or part of the family, but they may also be single, or even absent. Is there some kind of chalazal haustorium (see Srinivasachar 1940)? The outer epidermis of the outer integument of the ovule can have rather large cells (Juel 1929). The parietal tissue is ca 13 cell layers across in Colletia, although this may include a nucellar cap (Laguna & Cocucci 1971).
General information is taken from Brizicky (1964), Richardson et al. (2000a) and Medan and Schirarend (2004); Hegnauer (1973, 1990) summarized chemistry, Cremers (1973, 1974) growth of lianescent taxa, Bennek (1958) and Nair and Sarma (1961), floral morphology and anatomy, Schirarend and Köhler (1993a, b) and Gotelli et al. (2016a), pollen morphology, Medan (1985, 1988) discussed gynoecial development, Medan and Aagesen (1995), Vikhireva (1952: not read) and Medan and Hilger (1992) comparative floral and fruit morphology, Juel (1929) and Arora (1953) ovules and Gama-Arachchige et al. (2013) seed coat anatomy, esp. the water gap.
Phylogeny. There are three main clades in the family. Richardson et al. (2000b) found weak support for the basic relationships [rhamnoids [ziziphoids + ampeloziziphoids]], and relationships between the major clades in the ziziphoid group in particular were poorly understood. Basic relationships were better supported in Hauenschild et al. (2016a), and although there was some resolution of relationships in the rhamnoid and ziziphoid groups, the former had one major polytomy and the latter two. H.-L. Li et al. (2015) found the relationships [ziziphoids [rhamnoids + ampeloziziphoids]], and Schistocarpaea was sister to the zizyphoids examined; see also M. Sun et al. (2016). Ziziphus is wildly para/polyphyletic, species occurring in all the three main groups above (Islam & Simmons 2006; Hauenschild et al. 2016a; Z.-D. Chen et al. 2016: Hovenia similar).
For relationships in Pomaderreae, see Kellermann et al. (2005) and Kellermann and Udovicic (2008), for the phylogeny and morphology of Colletieae, see Aagesen (1999: 63 characters, morphological analyses) and Aagesen et al. (2005), and for Rhamnus and relatives, see Hauenschild et al. (2016b) and Y. Yang et al. (2019), although support for many relationships in the latter is weak.
Classification. For a phylogeny-based classification of the family, see Richardson et al. (2000a). The rhamnoids include three tribes, [Ventilagineae [Maesopsideae + Rhamneae]]. The ziziphoids are made up of five tribes, Phyliceae, Pomaderrieae, Gouanieae, Colletieae, and Paliureae, as well as unplaced genera like Ceanothus and Alphitonia, and include most of the rest of the family. The ampeloziziphoids include three tribes, three genera, and four species (Richardson et al. 2000b), which seems a trifle redundant. Hauenschild et al. (2016a) adopt the same classification.
[Elaeagnaceae [Barbeyaceae + Dirachmaceae]]: ?
Age. Bell et al. (2010) estimated this node to be (77-)65, 62(-51) Ma old.
ELAEAGNACEAE Jussieu, nom. cons. - Back to Rosales
Trees or shrubs; roots with N-fixing Frankia; dihydroflavonols?, 0-methyl flavonoids, ellagic acid +, myricetin 0; cambium storied; phloem stratified; true and fibre tracheids +, vestured pits + [not all], fibre pits bordered; wood with broad rays; sieve tube plastids lacking both starch and protein inclusions; nodes 1:1; petiole bundles arcuate or annular; no mucilage cells in leaves; hairs lepidote or stellate; leaves spiral or opposite, lamina vernation conduplicate-flat, margins entire, stipules 0; (plant dioecious - Hippophae); inflorescence a raceme, or flowers axillary; flowers (2-)4(-6)-merous; hypanthium long to short; P +, uniseriate, ± petal-like; A also 2 x P, borne in throat of tube; pollen 3-nucleate; G 1, stylulus long, stigma decurrent or capitate; compitum necessarily 0; ovule epitropous, micropyle?, outer integument 5-16 cells across, inner integument 3-4 cells across, funicular obturator +; megaspore mother cells several; hypanthium accrescent, fleshy, closely investing fruit; pericarp thin [Hippophae]; testa very thick, exotesta with sinuous anticlinal walls at least in part, (not palisade), mesotesta ± thick-walled; endosperm with chalazal haustorium, (starchy), cotyledons usu. unequal; n = 6, 10, 11, 13, 14, nuclear genome [1C] ca 0.58 pg.
3 [list]/45 (60): Elaeagnus (20-45). North Temperate, warm tropical; Malesia and Australia - also quite widely cultivated and/or escaped (map: from Meusel et al. 1978; Hultén & Fries 1986; Australia's Virtual Herbarium ix.2014). [Photos - Collection, Shepherdia Fruit © R. Kowal.]
Age. Bell et al. (2010) estimated that the age of the clade [Shepherdia + Elaeagnus] was (30-)20(-10) Ma.
Floral formula: * ⚥ P (5); A 5 alt. P, 10; N; G 1.
Ecology & Physiology. All genera are associated with N-fixing Frankia, and cluster roots have been reported from Hippophae (Shane & Lambers 2005); carboxylate exudation may help in phosphorus acquisition (Lambers et al. 2012b). The maximum age for the acquisition of this feature is (101.8-)91.1, 82.8(-64.5) Ma (H.-L. Li et al. 2015: support for sister-group relationship to Barbeya low)
Bacterial/Fungal Associations. Both ecto- and arbuscular mycorrhizal associations have been reported from Elaeagnaceae (e.g. Rose 1980). For the host preferences of rusts, see Savile (1979).
Chemistry, Morphology, etc. The androecium is obdiplostemonous according to Huber (1963). When stamens are equal in number to the perianth, they alternate with the lobes; this is consistent with an interpretation of P = K, with antepetalous stamens... Seed anatomy is rather like that of Rhamnaceae (Corner 1976).
For general information, see Bartish and Swenson (2004), for wood anatomy, see Jansen et al. (2000b) and for fruit and seed anatomy of Hippophae, see Harrison & Beveridge (2002).
Phylogeny. Elaeagnus is sister to the rest of the family (M. Sun et al. 2016).
Previous Relationships. Elaeagnaceae have been difficult to place. They were included in Proteales by Cronquist (1981) because of superficial floral similarities, and in Elaeagnales-Rhamnanae, next to Proteanae, in Rosidae, by Takhtajan (1997).
Synonymy: Hippophaeaceae G. Meyer
[Barbeyaceae + Dirachmaceae]: anther connective produced; ovules apotropous, outer integument 3-5 cells across, parietal tissue 5-6 cells across.
Evolution: Divergence & Distribution. Diversification here seems to have slowed down (Magallón et al. 2018).
Chemistry, Morphology, etc. In both families the embryo sac is quite deep seated, and in Dirachma socotrana in particular the suprachalazal nucellar tissue is very well developed.
BARBEYACEAE Rendle, nom. cons. - Back to Rosales
Trees; ellagic acid +; libriform fibres +; sieve tubes with compound perforations, sieve tube plastids with starch grains only; nodes 1:1; no mucilage cells in leaves; stomata laterocytic; hairs unicellular, spirally twisted; leaves opposite, lamina vernation supervolute-curved, margins entire, stipules 0; plant dioecious; inflorescence fasciculate, bracts and bracteoles 0; hypanthium 0; P +, uniseriate, sepal-like, 3-4; A (6-)9-12; pollen exine infratectum granulate-intermediate; nectary 0; G 1-2(-3), ± separate, styluli long, stigma long-clavate, decurrent, ?type; ovule subapical, micropyle long-endostomal, inner integument 5-6 cells across, nucellar cap ca 5 cells across, hypostase +; fruit a nutlet, P accrescent, wing-like; seed coat undistinguished, exotesta perforated, not palisade, anticlinal walls sinuous, endotegmen tanniniferous, anticlinal walls sinuous; n = ?
1 [list]/1: Barbeya oleoides. N.E. Africa, Arabia (map: from Aubréville 1974; Trop. Afr. Fl. Pl. Ecol. Distr. 5. 2010).
Floral formula: * [♂] [♀] P 3-4; A 9-12. /// P 3-4; G 1-2(-3).
Chemistry, Morphology, etc. The sieve tubes have compound perforations, unlike Ulmaceae and its immediate relatives and other Rosales.
The perforated seed coat is rather like that common in the Ulmaceae group (Bouman & Boesewinkel 1997).
Additional information is taken from Friis (1993: general), Dickison and Sweitzer (1970: morphology), Tobe and Takahashi (1990: hairs and pollen), and Bouman and Boesewinkel (1997: ovule and seed); Hegnauer (1990) has a little information on chemistry.
Previous Relationships. The monotypic Barbeyaceae were placed in Hamamelididae-Urticales by Cronquist (1981) and in Hamamelididae-Barbeyanae by Takhtajan (1997).
DIRACHMACEAE Hutchinson - Back to Rosales
Shrub; stalked glands +/0; chemistry?; phloem stratified; sieve tube ?plastids, ?non-dispersive protein bodies; nodes ?lacunar; mucilage cells in leaves; leaves spiral, stipules subulate, persistent; flowers single, terminal; epicalyx of 4-8 lobes (in middle of "pedicel"); flowers 5-8-merous; hypanthium short, (K-C tube +), K basally connate, C contorted, vasculature fan-shaped; nectaries on/near base of C, lacking stomata; androecium obdiplostemonous, anthers extrorse, long, opening from apex; G , deeply longitudinally ridged, opposite the K, style +, stigma clavate or elongated; ?ovule orientation, micropyle zig-zag, inner integument ca 2 cells across, nucellar cap 0, hypostase ?+; fruit beaked, segments opening from the base, wooly inside, columella +, K deciduous above the hypanthium; seeds laterally flattened, integumentary antiraphe bundle +, exotesta with anticlinal walls thickened, tegmen ?multiplicative, endotegmen tanniniferous; endosperm slight, embryo colour?; n = ?
1 [list]/2. Socotra, Somalia (map: from Link 1991b).
Floral formula: * ⚥ K (5-8); C 5-8; N; A 5-8 opp. C; G .
Chemistry, Morphology, etc. The single flowers may represent a reduced, cymose inflorescence, the epicalyx consisting of bracts and bracteoles (Ronse De Craene & Miller 2004: Dirachma socotrana). A hypanthium is described as involving just the sepals and petals but perhaps also the stamens (Ronse De Craene & Miller 2004: pp. 117, 123); it is unclear that there is much of a conventional hypanthium. Petal initiation is later than that of the stamens, as is common is rosids, and until quite late in development they are very much shorter than the stamens. There is a lot of starch in the pollen grains (Boesewinkel & Bouman 1997). The presence of an antiraphal vascular bundle means that the outer integument is very thick (6-9 cells or more) when viewed in the abaxial median plane; integument measurements are taken from the sides of the ovule (see Boesewinkel & Bouman 1997). There is a structure on the seed described as a small, funicular aril, perhaps similar to that found in some Rhamnaceae (Ronse De Craene & Miller 2004).
For additional information, see Link (1991b [c.f. 1990], 1994) and Bayer (2004), all general, Baas et al. (2001: wood anatomy), Ronse De Craene and Miller (2004: floral morphology), and Boesewinkel and Bouman (1997: ovule and seed).
Previous Relationships. The exotestal seeds with straight embryos suggest that Dirachma is not close to Geraniaceae (Geraniales), with which Dirachma had been linked, as by Cronquist (1981) - see e.g. Boesewinkel (1985) and Boesewinkel and Bouman (1997). Takhtajan (1997) included Dirachmaceae in his Malvales because of its similarity in gross morphology.below
[Ulmaceae [Cannabaceae [Moraceae + Urticaceae]]]: flavonols and their glycosides, myricetin [some Ulmaceae, Cannabaceae] +, ellagic acid 0; plant with ± watery exudate; hairs unicellular and multicellular-glandular; cambium ± storied; libriform fibres +; phloem stratified; cystoliths common, epidermal and hair cell wall silicification and calcification common; at least one prominent prophyllar bud; lamina with secondary veins proceeding straight to non-glandular teeth and higher-order veins convergent on those teeth [urticoid], stipules cauline; flowers small [7> mm across], usu. protogynous, often imperfect; hypanthium?, P +, uniseriate, sepal-like, imbricate; A equal and opposite P; staminate flowers: pistillode +; pollen porate, exine infratectum granular, intine thickening at the apertures [= oncus]; nectary 0; G , abaxial only fertile, stigma/styles spreading, receptive area extending down adaxial surface and ± confluent basally; ovule apical, pendulous; fruit a drupe; testa thin, vascularized, perforated [rarely in Ulmaceae]; x = 14.
Age. This node may be (61-)57-55(-51) Ma (Wikström et al. 2001), (76-)66, 64(-55) Ma (Bell et al. 2010), ca 70.9 Ma (Tank et al. 2015: Table S2) or ca 90 Ma (Manchester 1989b).
Evolution: Divergence & Distribution. The copious information (but there is less about embryology) on the four families awaits synthesis. Sytsma et al. (2002) should be consulted for details of character evolution; they note that inflexed stamens and their dehiscence, fruit type, and laticifers need detailed study (for the latter, see also Marinho & Teixeira 2018); hypanthium presence and other characters can be added to this list. Two-ranked leaves may be an additional synapomorphy (or pegged at a still higher level), as well as urticoid teeth. For the evolution of fruits, see Tiffney (1986a).
Dottori (1994) discussed the features separating the two parts of the old Ulmaceae, Ulmaceae s. str and Cannabaceae (Celtidaceae).
Pollination Biology & Seed Dispersal. For discussion of flowers and inflorescences, the insects that may breed in them, and pollination, see Berg (1990).
Ecology & Physiology. 12/42 of the commoner species in west Amazonian rainforests are members of this clade (as Urticales: Pitman et al. 2001).
Plant-Animal Interactions. Some Nymphalinae-Nymphalini butterflies and other nymphalids like Apaturinae, Libytheinae, Pseudoergolinae, etc., have larvae that eat members of these families (see also under Urticaceae) - but also on the immediately unrelated Euphorbiaceae (Malpighiales: see Ehrlich & Raven 1964). Similarly, aterpillars of Acraea (Acraeinae, also Nymphalidae) are quite common on Urticaceae (including Cecropia), and also on Moraceae, etc.; this particular genus is also commonly found on Passifloraceae and their relatives. The ancestor of Nymphalinae may have fed on Urticaceae and relatives (Nylin & Wahlberg 2008; Wahlberg et al. 2009; Nylin et al. 2014), and some members of the clade shifted to Lamiales around the K/P boundary (Nylin & Wahlberg 2008).
Chemistry, Morphology, etc. Raffinose and stachyose are common oligosaccharides in phloem exudate in Ulmaceae, Moraceae and Cannabaceae sampled (Zimmermann & Ziegler 1975). The group has homogeneous wood anatomy: Rays are relatively broad, pits are simple, intervessel pitting is alternate, fibres are septate, and parenchyma is paratracheal (Baas et al. 2000). For torus-margo pits, see above. Minerals of various kinds are deposited in the leaves. and phytoliths are common in this clade (Piperno 2006; see Satake 1931 for spodograms). Globose to elongated cystoliths are common, and they are amorphous CaCO3 concretions with a stalk and/or centre part made up of silica (Pierantoni et al. 2018 for cystoliths and other kinds of foliar mineralizations in Ficus).
Because of the well-developed prophyllar bud(s), the inflorescences are often paired, with a bud between them (Berg 1989), and/or the branches may have a bud on one or both sides at the base. Ulmus does not appear to show this arrangement, and it is tentatively placed as an apomorphy at the [Cannabaceae [Urticaceae + Moraceae]] node below. The "stipular buds" of Cannabis (Miller 1970 and references) are really prophyllar buds.
It is not clear which taxa have a hypanthium; at least some species of Ulmus and Pilea do, but other species of Ulmus, Zelkova, Ampelocera and Trema show no obvious signs of one (see also Bechtel 1921; Leme et al. 2018). Staedler (1923) discussed the absence of an anther epidermis, although it is present in Ficus (other Rosales?); there is no obvious link with dehiscence mechanism. Starchy pollen is common, but apparently not in Urticaceae. Bechtel (1921) and Eckardt (1937) described gynoecial morphology in considerable detail. Taxa with a perforated testa are quite common, although this feature may have arisen more than once (Kravtsova & Oskolski 2007; Yang et al. 2013).
Note that older literature on Urticales refers to this whole clade and that on Ulmaceae may also include information about Cannabaceae (esp. Celtis and relatives). For further information, see Berg (1989: general), Tippo (1938) and Sweitzer (1971), both anatomy, Giannasi (1978, 1986: chemistry), Terabayashi (1991: vernation), Hennig et al. (1994: cuticle waxes), Tobe and Takaso (1996) and Behnke and Barthlott (1983), both hairs, Berg (1990: inflorescences and pollination),Punt and Malotaux (1984: pollen), Omori and Terabayashi (1993: gynoecial vascular anatomy), Mohan Ram and Nath (1964) and Dottori (1994), both embryology, Kravtsova and Wilmot-Dear (2013: fruit anatomy) and Takaso and Tobe (1990: testa).
Phylogeny. Relationships in this group are discussed above.
ULMACEAE Mirbel, nom. cons. - Back to Rosales
Trees, (deciduous); (growth sympodial, apex of innovation aborts); (ectomycorrhizae +); lignans +; (wood fluoresces); unicellular hairs smooth; torus-margo pits +; cystoliths usu. pegless; terminal bud of innovation aborts; leaves two-ranked, lamina vernation laterally (vertically) conduplicate-plicate, secondary veins going into teeth, (margin entire), stipules extrapetiolar; flowers perfect and mixed; 4-5(-8)-merous; P spiral, (connate); A (3-)5-8(-16), extrorse; tapetal cells 2-3-nucleate; endothecial thickenings U-shaped; pollen 4-7-porate, exine rugulose; at least one stigma/style with 3(-5) vascular bundles; ovule (with bistomal micropyle), outer integument 4(-6 - Holoptelea) cells across, inner integument ca 4 cells across, (integument 1, 7-10 cells across, Phyllostylon), parietal tissue ca 5 cells across, nucellar cap ca 2 cells across; (embryo sac tetrasporic, Drusa/Adoxa types - Ulmus, Zelkova); fruit also a (asymmetric) samara; seeds flattened, coat undistinguished, exotestal cells elongated, unthickened; chalazal endosperm haustorium +, (polyembryony +), (embryo curved - Zelkova); genome [1C] ca 1.08 pg; often terminal/subterminal diffuse-complex centromeres; 69bp ndhF deletion; (germination cryptocotylar - Phyllostylon).
6 [list]/35-45: Ulmus (20-30, species limits uncertain), Ampelocera (12). Mostly N. Temperate, esp. Asian, few species tropical, not in Australia and the Pacific (map: from Soepadmo 1977; Hultén & Fries 1986; Fl. N. Am. 3. 1997; Todzia 1989, 1992: Trop. Afr. Fl. Pl. Ecol. Distr. 5. 2010). [Photos - Collection.]
Age. Ulmus is known as leaves and fruits from Early Eocene deposits of northeastern China some 50 Ma old (Wang et al. 2010; see also Friis et al. 2011 for Caenozoic fossils), the age of the genus in Manchester (1989a) was around 57 Ma. This suggests an appreciably greater age for crown-group Ulmaceae as a whole.
Evolution: Divergence & Distribution. For a review of the fossil history of Ulmaceae, see Manchester (1989b), and for Cedrelospermum, crown-group Ulmaceae, around 48 Ma and widely distributed in the Northern Hemisphere, see Manchester (1989a) and Jia et al. (2018).
The family has two main clades. One, including Ampelocera, Phyllostylon and Holoptelea, is largely tropical, and the other is north temperate (Neubig et al. 2012b).
Pollination Biology & Seed Dispersal. Breeding systems in the family are variable, but at least some flowers are perfect. Seeds seem to remain viable for ca 1 year only (Dottori 1994).
Chemistry, Morphology, etc. There are distinctive fatty acids in the seeds of some Ulmaceae, but not in those of Cannabaceae or Moraceae (Badami & Patil 1981: sampling). The terminal buds of the innovations abort (Berg 1989). Ulmus lacks well-developed prophyllar buds and has one of the two stipules intrapetiolar, they are both intrapetiolar in seedlings of some species, and the leaves may also be opposite, as in seedlings. Hemiptelea has pegged cystoliths.
For the literature on embryo sac morphology in Ulmus and Zelkova, see Dottori (1991); Nawaschin (1895) suggested that chalazogamy occurred in Ulmus. Holoptelea has a thick-walled exotesta.
For general information, see Todzia (1993), for floral morphology, see Leme et al. (2018: Ampelocera), for embryology, see Dottori (1991, 1994), for gynoecial morphology, see Okamoto et al. (1992), and for a summary of fruit morphology, see Herrera et al. (2014).
Phylogeny. The poorly-known Ampelocera is to be included here (see Ueda et al. 1997b; also Wiegrefe et al. 1998); although its hairs are smooth, its leaves have ascending veins. A clade including [Ampelocera [Phyllostylon + Holoptelea] is sister to [Hemiptelea [Zelkova + Ulmus]] (Sytsma et al. 2002; Neubig et al. 2012b; see also M. Sun et al. 2016).
[Cannabaceae [Moraceae + Urticaceae]]: C-glycoflavones also +; (sieve tube plastids with starch grains); unicellular hairs usu. micropapillate; secondary veins palmate, stipules cauline-intrapetiolar; plant monoecious; (inflorescences paired at nodes) [?level]; staminate flowers: P = A, filaments incurved in bud [explosively straightening]; carpellate flowers: stigma/styles with single vascular bundle; fruits not or barely flattened; embryo curved.
Age. The age for this clade has been estimated at (52-)49, 42(-39) Ma (Wikström et al. 2001: c.f. topology), (65-)56, 54(-45) Ma (Bell et al. 2010), or around 59.2 Ma (Tank et al. 2015: Table S2).
Evolution: Pollination and Seed Dispersal. Pedersoli et al. (2019: see also references) give details of explosive pollen release in taxa of all three families. Among other aspects of this process, they emphasize the occurrence of mucilage-producing cells (these may be in different parts of the flower), the mucilage perhaps causing the pollen grains to aggregate and so to get thrown further when the filaments abruptly straighten. The adaxial cells of the incurved filaments are turgid, and get thrown into deep folds, these disappearing on the straightening of the filaments. Furthermore, the pistillode is often an integral part of the dehiscence mechanism, being hollow and/or with an apical cavity, and the pistillode often deflates during the explosion process. The perianth members are rigid (and basally connate in Moraceae and Urticaceae) and stop the movement of the filament as it straightens, causing the anthers to invert and throw out the pollen. Interestingly, the stamnens explode sequentially (Pedersoli et al. 2019).
Members of all three families are quite often dispersed by bats in the New World (Lobova et al. 2009). Trema, Ficus and Cecropia are all important food sources for frugivorous birds (Snow 1981).
CANNABACEAE Martynov, nom. cons. - Back to Rosales
Trees (twining lianes), (± herbaceous); (plant ectomycorrhizal); (flavonoids), sesquiterpene lactones +, (flavonols 0); (torus-margo pits + - Celtis), true tracheids +; (sieve tubes lacking non-dispersive protein bodies); cystoliths usu. with pegs [distribution?]; leaves (spiral; opposite), lamina vernation (laterally) conduplicate-plicate (conduplicate; supervolute); (lamina strongly palmately lobed or compound, veins proceeding to the apex of lobes - Cannabis, Humulus), stipules connate or not; P (2 - carpellate flowers Cannabis, Humulus), (valvate); tapetal cells 2-4-nucleate; endothecial thickenings U-shaped/annular/spiral; pollen 3(-2) porate, exine scabrate to verrucate; micropyle bistomal/zigzag, outer integument 2-4(-8) cells across, (elaborate - Celtis), inner integument 2-3 cells across, parietal tissue 4-6 cells across, nucellar cap 2-6 cells across; embryo sac haustorium +; fruit (achene, samara); exotestal cells tangentially elongated, with arms, unthickened; (polyembryony +), embryo also coiled; n = (8-11, 13-15), centromeres medial/submedial (not Gironniera), simple.
11 [list]/170 (100): Celtis (ca 100). Worldwide, but not Arctic, distribution of Humulus lupulus in Asia is unclear (map: from Wickens 1976; Soepadmo 1977; Hultén & Fries 1986; Fl. Austral. 3. 1989; Fl. N. Am. III 1997; Trop. Afr. Fl. Pl. Ecol. Distr. 5. 2010). [Photos - Collection, Celtis Flower.]
Age. The age of the clade excluding the three basal genera mentioned below is estimated to be (47-)37, 36(-26) Ma (Bell et al. 2010).
Evolution: Divergence & Distribution. For a review of the fossil history of Cannabaceae, see Manchester (1989b: as Ulmaceae); fossil pollen from the Turonian some 90 Ma is placed in this family, and the first fossils attributed to an extant genus belong to Gironniera that were found in European Maastrichtian deposits of some 48 Ma. Note that Boutain (2016) suggested a late Cretaceous age for Cannabaceae s. str., i.e. the [Cannabis + Humulus] clade. The Caenozoic fossil history of Cannabaceae that are now East Asian endemics is discussed by Manchester et al. (2009); see also the general summary in Friis et al. (2011).
For the optimization of a number of characters on this part of the tree, see Yang et al. (2013).
Ecology & Physiology. The liane, Celtis iguanea, is a reliable keystone food resource in Cocha Cashu, Peru, along with two species of Ficus, not so reliable, and a few other species (Diaz-Martin et al. 2014).
Pollination and Seed Dispersal. For details of explosive pollination, see above, also Cuéllar (1967). Note that Todzia (1993) noted that the stamens were straight, as did Kubitzki (1993), although the latter was reporting on Cannabaceae s. str..
Fruits of Trema are favoured by frugivorous birds of all sort, both specialists and generalists (Snow 1981).
Plant-Animal Interactions. Caterpillars of most Apaturinae (Nymphalidae) are found on Cannabaceae, although those of Hestinalis eat Urticaceae, Sephisa, Fagaceae, while Apatura, the spectacular purple emperor, has moved on to salicin-containing Salicaceae (Salix and Populus: Ohshima et al. 2010).
Bacterial/Fungal Associations. Parasponia andersonii (= Trema) is the only non-legume nitrogen fixer that is associated with other than actinomycetes, and its rhizobia - a variety of taxa are involved - remain in infection threads like those of some Fabaceae, especially basal Caesalpinioideae. Unlike Fabaceae, lipochitooligosaccharide recognition leading to nodule formation as well as arbuscular mycorrhizal symbioses are controlled by the same receptor kinase enzyme; infection of the plant is by entry through cracks in the epidermis. The nodules are modified lateral roots and have central vascular tissue, the bacteria being in the cortex; this is unlike the nodules of Fabaceae but like Frankia-induced nodules elsewhere in the N-fixing clade (Streng et al. 2011; Behm et al. 2014 for literature). However, a set of some 290 symbiosis genes are involved in N-fixation in both P. andersonii and legumes (Medicago), while NFP2, NIN and RPG genes, all essential for the establishment of N-fixing nodules, are found as pseudogenes in at least half of the six non N-fixing members of Rosales outside Cannabaceae that were examined (van Velzen et al. 2018). The haemoglobins involved in oxygen transport in this system seem to have evolved independently of haemoglobins with similar role in other N-fixing systems (Sturms et al. 2010). Van Velzen et al. (2018) suggest that there may have been a change in symbiont from Frankia to rhizobium in a recent ancestor of P. andersonii in addition to repeated losses of the ability to fix N in other Rosales, not independent acquisitions of N-fixation via Rhizobium here and in Fabaceae as if some underlying tendency were involved (e.g. Soltis et al. 1995b; Werner et al. 2014).
Gironniera is reported to be ectomycorrhizal (Smits 1994).
Genes & Genomes. Cannabis and Humulus have an X-autosome balance system determining the 'sex' of the plant [ref.]. n = 10 is common in Cannabaceae.
Economic Importance. For the biology of Cannabis sativa, see Small (2015), it provides oil, grain, high-quality fibres (hemp) and hallucinogens (marijuana). Cannabidiolic acid (CBDA) is favoured over delta-9-tetrahydrocannabinolic acid (THCA) in medications, but CBDA is produced in only "modest" quantities by hemp, very little THCA being produced, but the latter, and cannabinoids in general, are produced in large quantities by marijuana plants. Recent interest in CBDA has led to the development of cultivars in which some of the hemp genome containing genes involved in the synthesis of CBDA have been introgressed into the marijuana genome (Grassa et al. 2018).
Chemistry, Morphology, etc. Only the "basal" Aphananthe and Gironniera have flavonols. Whether the laticifers of Cannabis etc., really are similar to those of Urticaceae and Moraceae must be confirmed; there is no milky exudate and they occur throughout the plant, and given the derived position of Cannabis, they may have evolved independently. Humulus, with its opposite leaves, has split laterals/a commissural vascular bundle (Colomb 1887). The "distinctive" camptodromous (to semicraspedodromus) venation of Celtidaceae s. str. is disturbed by the inclusion of Cannabis, etc., in this clade, however, strictly craspedodromous venation is reported from Palaeocene Celtis itself (Manchester et al. 2002).
The anticlinal walls of the testa of Humulus are sinuous and its embryo is green. Little seems to be known about the embryology of Cannabaceae, but there are reports of e.g. chalazogamy in Celtis occidentalis, an antipodal haustorium in the embryo sac of of Cannabis, etc. (see e.g. Modilewski 1908).
For general information, see Grudzinskaya (1967), Todzia (1993: as Ulmaceae), and Kubitzki (1993b: as Cannabaceae), for chemistry, see Hegnauer (1973, 1990, as Ulmaceae; also 1964, 1989), also Mohan Ram and Nath (1964: Cannabis ovules and seeds), Leins and Orth (1979: Cannabis flowers), Modilewski (1908) and Dottori (1991, 1994), all embryology, and Kravtsova and Wilmot-Dear (2013: fruit anatomy).
Phylogeny. Pteroceltis, Humulus, and Cannabis are close, and they and some other members of this clade have sieve tube plastids with starch grains (Behnke 1989). Studies suggested that Lozanella was sister to Aphananthe or sister to the rest of the family (Wiegrefe et al. 1998; Soltis et al. 2002), but Yang et al. (2013; see also van Velzen et al. 2006; H.-L. Li et al. 2015; M. Sun et al. 2016) found that Aphananthe was well supported as sister to the rest of the family, with either Lozanella and/or Gironniera sister to the remainder, while in a plastome analysis H. Zhang et al. (2018: plastome analyses) found the well-supported relationships [Aphananthe [[Lozanella + Gironniera] [the remainder]]]. Trema is paraphyletic, the N-fixing Parasponia being embedded in it (Sytsma et al. 2002; van Velzen et al. 2006; Yang et al. 2013; van Welzen et al. 2018), while the position of Celtis was only weakly supported in the study by H. Zhang et al. (2018).
Synonymy: Celtidaceae Link, Humulaceae Berchtold & J. Presl, Lupulaceae Link
[Moraceae + Urticaceae]: latex system + [± throughout the plant]; (calcium carbonate crystals); P valvate (imbricate), basally connate or not; staminate flowers: pollen 2- or 5-porate; pistillode +; seed coat undistinguished.
Age. Zerega et al. (2005) suggested that the age of this node was at least 89 Ma, while around 58.8 or 55.3 Ma are ages in Tank et al. (2015: Table S1, S2), (73.4-)70.9(-68.5) Ma in Magallón et al. (2018) and (93.3-)87.5(-81.7) Ma in Q. Zhang et al. (2018).
Evolution: Divergence & Distribution. There may be an uptick in the diversification rate at this node some (73.4-)70.9(-68.5) Ma (Magallón et al. 2018).
There is a group of genera of Moraceae with explosive pollen dispersaland they were included in the paraphyletic Moreae that was part of a basal polytomy within Moraceae in early phylogenetic reconstructions of the family. For dioecy, see Datwyler and Weiblen (2004).
Genes & Genomes. Rates of molecular evolution are likely to have increased at least twice in this clade, e.g. in most Urticaceae and also in Dorstenia, the increase being associated with the adoption of the herbaceous habit (Smith & Donoghue 2008).
Chemistry, Morphology, etc. Marinho and Teixeira (2018) discuss the anatomy of the latex system and its distribution in various parts of the flower, finding that in some Urticaceae laticifers occur both in the perianth and inflorescence axis, not just in the bark, as was previously thought, moreover, they note that lipids are common in the latex of Moraceae, phenolics in that of Urticaceae. Laticifers are less branched in Urticaceae. Details of the distribution of laticifers may also be interesting: they are absent from the flowers of Urticaceae-Cecropieae studied, they are generally present at least in the carpellate flowers in Moraceae, but they were absent from the flowers of the one species of Ficus studied (Marinho & Teixeira 2018).
Scattered in the group are taxa in which the tepals are persistent (e.g. Pilea) or accrescent (e.g. Morus), and in the latter the fruits are anthocarps in the strict sense. For inflorescence development, which can be very similar in genera in the two families, see Bernbeck (1932).
Phylogeny. For a morphological phylogeny focussing on Urticaceae s.l., i.e. Moraceae and Urticaceae here, see Kravtsova and Oskolski (2007).
Classification. The two families have much in common, and Corner (1952) even included Moraceae in Urticaceae. One might go further - Lozanella, with its opposite leaves and boxy venation, looks rather like Urticaceae, but it is a member of Cannabaceae...
MORACEAE Gaudichaud, nom. cons. - Back to Rosales
Largely woody; (isoflavonoids +); (cork in outer cortex); latex milky; (stomata aniso- and cyclocytic); leaves spiral, lamina vernation variable; inflorescences congested, often ± spicate [staminate] or ± globose [carpellate]; flowers 4-merous, (P 0-10); staminate flowers: bracts peltate; P free; carpellate flowers: P connate; (G inferior), styles 1 or 2, often unequal; ovule (subapical; campylotropous), outer integument 3-4 cells across, inner integument ca 3 cells across, nucellar cap ca 5 cells across [nucellar beak]; infructescence/fruit various; exotesta ± tanniniferous; (n = 12 upwards, esp. 13, 14), chromosomes 0.5-2.7 µm long, both terminal and median centromeres.
39 [list: to tribes]/1,125 - seven groups below. Mostly tropical to warm temperate (map: from Jalas & Suominen 1976; Wickens 1976; Frankenberg & Klaus 1980; Fl. Austral. 3. 1989; Fl. N. Am. 3. 1997; Wilmott-Dear & Brummit 2007: Asia and South America only approximate).
Age. Zerega et al. (2005) dated crown-group Moraceae to (110-)89.1(-72.6) Ma, while (100.6-)93.1(-85.9) Ma is the age in Gardner et al. (2017) and (84.7-)79(-73.2) Ma that in Q. Zhang et al. 92018) . However, given that Misiewicz and Zerega (2012) date crown-group Dorstenia to (132.0-)112.3(-84.8) Ma, the sky might be the limit.
[Maclureae [Artocarpeae + Moreae]]: ?
1. Maclureae Clement & Weiblen
Trees to shrubs (lianes), axillary thorns +; stipules often small; plant dioecious; inflorescence globose, with golden dye, globose; staminate flowers: bracts not peltate, (filaments straight); carpellate flower: (bracts peltate) stigmas unequal (1); "fruit": perianth fleshy, adnate to G or not, fruit (a drupe).
1/11. Tropical, 1 species to temperate North America. [Photo - Inflorescence].
Age. The age of crown group Maclureae is (73.4-)61(-49.1) Ma (Gardner et al. 2017), ca 50 Ma (Zerega et al. 2005) or as little as (41.1-)24.7(-8.9) Ma (Q. Zhang et al. 2018).
[Artocarpeae + Moreae]: carpellate flowers: "fruit": P accrescent.
Age. This clade has been estimated to be (92.7-)83.8(-74.8) Ma (Williams et al. 2017) or ca 84 Ma (Gardner et al. 2017).
2. Artocarpeae Lamarck & de Candolle
(Lianes); lamina (with glandular spots with a waxy surface), (stipules ensheathing stem [amplexicaul]); (P connate, that of adjacent flowers adnate in the middle portion [completely]); staminate flowers: 2 merous; A 1(-3), filaments straight, ?pistillode; (exotesta several thickened layers - Prainea s. str.); "fruit": infructescence axis fleshy; germination hypogeal.
3/76: Artocarpus (ca 70). Indo-Malesia (Artocarpus) and Central and South America. Photo: Fruit].
Age. Crown-group Artocarpeae are (65-)59.7(-55.2) Ma (Williams et al. 2017), (78.5-)69.6(-61.4) Ma (Gardner et al. 2017), (80.6-)65.1(-52.2) Ma (Zerega et al. 2005), or (68.6-)65.6(-64) Ma (Q. Zhang et al. 2018).
Synonymy: Artocarpaceae Berchtold & J. Presl
3. Moreae Dumortier
Plant (with thorns), (herbaceous - Fatoua); lamina venation (palmate), vernation conduplicate-plicate; plant dioecious (monoecious); inflorescence spicate to globose; staminate flowers: (bracts not peltate); (filaments straight); (pistillode 0); carpellate flowers: style (1); "fruit": perianth fleshy, fruit dehiscent drupe/drupe/berry, (endosperm +).
7/56: Streblus (23). Tropical, especially Asia to Australia, some temperate.
Age. This clade has been estimated to be (77.3-)67.1(-57) Ma (Gardner et al. 2017), (75.2-)58.6(-44.2) Ma (Zerega et al. 2005) or only (46.8-)40.3(-34.9) Ma (Q. Zhang et al. 2018) .
[Parartocarpeae [Dorstenieae [Ficeae + Castilleae]]]: ?
4. Parartocarpeae Zerega & E. M. Gardner
Lamina (margin entire); plant monoecious; inflorescences globose, unisexual, involucre uniseriate; bracts ?0; flowers ?sunk in receptacular tissue, P ?0; staminate flowers: A (1-)2(-3), filaments straight, anthers extrorse, pistillode 0; "fruit": ; germination epigeal.
2/4. Peninsular Myanmar and Peninsular Thailand, Malesia, Solomon Islands.
Age. The age of this clade is (45.4-)30.2(-17.1) Ma (Gardner et al. 2017).
[Dorstenieae [Ficeae + Castilleae]]: radial latex tubes +; plant monoecious, inflorescence bisexual; inflorescence axis expanded; pistillode conical.
5. Dorstenieae Dumortier
(Herbs, rhizomatous/tuberous), (stem ± swollen); lamina (palmately compound), (peltate), (stipules 0 - Fatoua); plant monoecious (dioecious/andromonoecious); inflorescence axis disciform to globose; staminate flowers: (3-merous), (P connate); filaments (straight)/(curved, not explosive - Dorstenia), pistillode 0; (pollen pantoporate); carpellate flowers: (2-merous), (embedded in receptacle); ovule apotropous, campylotropous, (with massive swelling on one side [see below]), parietal tissue 4-10 cells across; antipodals 8-25; "fruit": P adnate to fruit, fruit a dehiscent drupe; (endosperm + - Dorstenia); n = 12-16, etc..
13/145: Dorstenia (105). Pantropical. Photo: Fruit.
Age. Crown Dorstenieae are ca 71 Ma (Zerega et al. 2005), (72.5-)61.5(-50.6) Ma (Gardner et al. 2017), or (70.2-)60.5(-51.4) Ma (Q. Zhang et al. 2018).
Synonymy: Dorsteniaceae Chevallier
[Ficeae + Castilleae]: insect pollination +; involucre pluriseriate, bracts imbricate; staminate flowers: filaments straight, pistillode often 0 or rudimentary; carpellate flowers: bracts not peltate [inc. Maclureae, etc.?]; P free.
Age. The age of this clade is estimated to be (88.2-)72(-59.6) Ma (Zerega et al. 2005), (68.6-)62.2(-56) Ma (Q. Zhang et al. 2018), (65.8-)57.8(-50.1) Ma (Gardner et al. 2017) or (66.2-)59.3(-52.7) Ma (Pederneiras et al. 2018).
6. Ficeae Dumortier
Also hemiepiphytes, lianes, stranglers, etc.; (phenanthroindolizidine alkaloids +), (cysteine proteases +), (latex 0); (leaves opposite), with petiolar or laminar gland [?= nectary]; lamina (venation ± palmate), (vernation conduplicate-plicate), glandular spots with a waxy surface, stipules ensheathing stem [amplexicaul], open in leaf axil; (plant dioecious); inflorescence axis hollow-spherical, flowers enclosed; staminate flowers: aggregated around ostiole (not); bracts not peltate; P 2-4, connate or not; A 1-2, (unithecate); pistillode 0/+; carpellate flowers: P 3-5, connate or not; staminodes 0; style branches unequal or not, stigma (tubular/infundibular), dry; "fruit": infructescence axis fleshy [= a syconium], fruit an achene.
1/800. Pantropical. Photo: Fruit.
Age. Estimates of the age of crown-group Ficus range from around 86.7 to (92.6-)69.9(-60) to (80.8-)63.4(-47.8) Ma (L. Xu et al. 2011, Chantarasuwan et al. 2016, and Machado et al. 2018 respectively), (51-)43.3(-40.1) Ma (Zerega et al. 2005) and (42.8-)28.7(-15.8) Ma (Gardner et al. 2017); Cruaud et al. (2012b) suggest an age of (101.9-)74.9(-60.0) Ma, while (50.4-)42.8(-34.5) Ma is the estimate in Pederneiras et al. (2018) and (55.9-)48.5(-40.6) Ma that in Q. Zhang et al. (2018).
Synonymy: Ficaceae Berchtold & J. Presl
7. Castilleae C. C. Berg
(Branches spreading), cladoptosis + (- Poulsenia, Antiaropsis); (cystoliths 0); stipules ensheathing stem [amplexicaul]/not; plant dioecious; inflorescence involucrate, unisexual, axis disciform to hollow-spherical, flowers enclosed; P connate (free - Antiaropsis); ; staminate flower: bracts 0/trilobed; pistillode 0; carpellate flowers: (bracts 0); "fruit": (inflorescence axis fleshy), (P adnate to fruit), fruit a drupe.
11/62. Pantropical, esp. America.
Age. Estimates of the age of crown-group Castilleae are (68.5-)53.3(-39.8) Ma (Zerega et al. 2005), (47.1-)34(21.3 Ma (Gardner et al. 2017) or (47-)31.2(-18.7) Ma (Q. Zhang et al. 2018 - the stem is about 30 My).
Evolution: Divergence & Distribution - General (for Ficus, see below). For additional dates, see e.g. Q. Zhang et al. (2019). Berg (2005) suggested that diversification in Moraceae occurred on a still physically coherent tropical supercontinent, but Zerega et al. (2005) advanced a more complex hypothesis to explain the distribution and diversification of the family.
Berg and Hijman (1999) suggested that the distribution of Dorstenia, found in both Africa and South America, could be explained by continental drift; Zerega et al. (2005), however, estimated the crown-group age of the genus to be a mere 18.4-3.5 Ma, and Berg and Hijman's suggestion is also incompatible with ages in Gardner et al. (2017). However, in a more complete analysis, Misiewicz and Zerega (2012) dated the crown age of Dorstenia at (132.0-)112.3(-84.8) Ma, with the age of the New World crown group, (44.8-)30.3(-16.5) Ma - and in fact the latter was the age that Zerega et al. (2005) had earlier thought might be the crown-group age for the wholegenus, given their sampling. Dorstenia may have originated in Africa, moved to the New World, and then back to Africa (Misiewicz & Zerega 2012). Woody taxa are basal in the genus, which otherwise is largely herbaceous, unusual for Moraceae, and includes stem succulents, rhizomatous and tuberous plants, and even an annual species (Berg & Hijman 1999).
Although Borneo is the centre of diversification for Artocarpus, the genus may have moved there from the New World (Williams et al. 2017).
Dioecy may be the plesiomorphic condition for the family, although that depends in part on how gains and losses of dioecy are weighted and of course on the phylogeny (Datwyler & Weiblen 2004; Q. Zhang et al. 2018: likely), and these authors suggest that there have been five or so transitions to monoecy with various reversals and further transitions - certainly, dioecy is no dead end (see also Goldberg et al. 2017; Sabath et al. 2015). For a possible association between monoecy and rather higher diversification in Ficus, see Bruun-Lund et al. (2017b).
Ecology & Physiology. Moraceae are the second to eighth most speciose family in lowland tropical rainforest in both America and Africa, and in Amazonian forests they include a disproportionally large number of the species (11/227) that make up half the stems 10 cm d.b.h. or more (Gentry 1988; ter Steege et al. 2013).
Very high photosynthetic rates have been recorded from some species (references in Pierantoni et al. 2018). Most species have cystoliths on one or both sides of the leaf blade, and these may be involved in redistributing light in the blade - although some species, including F. religiosa, lack them, so absolute statements about any functions of these and other mineralizations in the lamina are difficult to make (Pierantoni et al. 2018).
Pollination Biology & Seed Dispersal. The early evolution of the fig/fig wasp association is unclear (see below), but there are other remarkable pollination systems in Moraceae. Ficus is sister to Castilleae. Female inflorescences of Castilleae such as Antiaropsis are urceolate. The pollinators (thrips) breed among the flowers of the male inflorescences, eating pollen, etc., pollination occurs when the pollen-coated thrips visit female inflorescences (Datwyler et al. 2003; Datwyler & Weiblen 2004; esp. Zerega et al. 2004; Clement & Weiblen 2009); insect pollination here is a reversal from wind pollination. Pollination of Artocarpus integer is by dipteran cecidomyiid gall midges: The larvae eat fungi growing on the male inflorescences, and pollination occurs when the adult midges visit female inflorescences, perhaps attracted by scent (Sakai et al. 2000; see also Gardner et al. 2018). Pollination in Dorstenia is poorly known, but apomixis and myophily have both been suggested - flies may lay eggs in the inflorescences, pollinating as they do so (de Araújo et al. 2017). P. E. Taylor et al. (2006) describe explosive pollen release in Morus alba; for further details of similar pollen release in other taxa, see above. Q. Zhang et al. (2018) discuss the evolution of breeding systems in the family as whole, but with a focus on Ficus.
Seed dispersal in Moraceae is often by animals, but just what part of the plant contributes to the fleshiness that attracts the disperser varies. In Morus the fruits, achenes, are surrounded by the fleshy perianth and are closely packed on an erect inflorescence axis. The more or less elongated inflorescences of Artocarpus - it includes the bread and jack fruits - can weigh up to 50 kg, and the fleshy part is made up of both the perianth members and the inflorescence axis itself (see Zerega et al. 2010: phylogeny and morphology). Broussonetia papyrifera has heads of bright red, dangling drupes, while Dorstenia, etc., have "dehiscent drupes" in which the stone is shot out of the turgid fruit, the separation following a line of weakness in the mesocarp tissue (Schleuss 1958). In both these cases the developing fruits are initially extruded by the turgid, closely-packed perianth members. For additional information about seed dispersal here, see de Araújo et al. (2017: q.v. for variants) and Thorogood et al. (2018: Dorstenieae not sister to Ficeae). In Antiaropsis (Castilleae) the inflorescence axis is concave at first, but spreading ("dehiscing") when ripe, when the drupes contrast in colour with the bracts, etc. (e.g. Zerega et al. 2004).
Maclura pomifera is known for its large, multiseeded infructescences (the perianth is fleshy) 15 cm or more across that may have been dispersed by now-extinct megafauna - they may also have dispersed other species in the genus, although infructecences there are less than 7 cm across (Gardner et al. 2017: see also Arecaceae fruits). Maclura is a small but old genus (Gardner et al. 2017), nevertheless, crown-group ages make drift an unlikely explanation for current distributions here.
Plant-Animal Interactions. Bombyx mori (the silkworm) caterpillars can eat quite a number of species of Moraceae, but not those of most other members of the Ulmaceae group - although they will grow on Ulmus itself (Fraenkel 1959). Caterpillars of danaine butterflies quite commonly eat Moraceae; both they and their usually preferred Apocynaceae are rich in latex, although Moraceae do not often have the cardenolides that are quite common in Apocynaceae (Ackery & Vane-Wright 1984).
Evolution: Divergence & Distribution - Ficus. There are various ideas about the biogeographical history of Ficus (Chantarasuwan et al. 2015 and references). The origin of crown group Ficus may be in Late Cretaceous Eurasia, while most diversification has been in the Caenozoic, dispersal rather than vicariance best explaining details of the current distribution of the genus (Cruaud et al. 2012b). Subgenus Pharmacosycea is restricted to the New World, as is Urostigma section Americana, the latter being sister to the African section Urostigma, while Urostigma-Malvanthera is Australasian (e.g. Cruaud et al. 2012b; Bruun-Lund et al. 2017b; Machado et al. 2018). Ficus may have moved directly to America from Africa (Machado et al. 2018) and also via the North Atlantic (Pederneiras et al. 2018, q.v. for details of the biogeography of the genus). Lopez-Vaamonde et al. (2009) discuss dating and biogeography of fig wasps, closely associated with Ficus, suggesting that their ancestors lived in Asia, dispersal rather than Gondwanan break-up being important for their subsequent distribution (see also Cruaud et al. 2012b); Xu et al. 2012 suggested a Gondwanan ancestry, but with much subsequent dispersal.
Diversification seems to have been largely constant over the >70 Ma life of the genus (Bruun-Lund et al. 2017b), although there may have been small positive rate shifts in America. Moraceae, and in particular Ficus, includes a number of (hemi)epiphytes, stranglers and lianes (for how Ficus pumila climbs, see Groot et al. 2003). Machado et al. (2018) and Bruun-Lund et al. (2017b) discuss ecological interactions, particularly the role of hemiepiphytism, and diversification; overall, hemiepiphytes tend to have larger ranges if lower population densities than other taxa and dioecious figs may be more local than monoecious figs, the pollinators of the latter dispersing more widely (Harrison & Rasplus 2006; Bruun-Lund et al. 2017b); and for interactions between figs and frugivores, see below. Ca 29 Ma is the age for the node [F. carica + F. insipida] (Gardner et al. 2017).
The fig/fig wasp association might seem to be an excellent example of an obligate one-on-one association between the plant and pollinator (e.g. Herre 1996 and references): There is strict co-evolution, both figs and their pollinating agaonid wasps are monophyletic, and the two speciate almost in synchrony. Indeed, there is at least a general association between species of figs and species of wasps, and in groups like section Ficus sect. Galoglychia cospeciation is likely, even in the non-pollinating wasps that are also members of the system (Jousselin et al. 2008; Cruaud et al. 2012a, b; c.f. Cook & Segar 2010 in part). However, things are not so simple. Recent work suggests that there may be rather less specificity in the association between fig and wasp than was previously thought (Cook & Rasplus 2003; Machado et al. 2005; Jackson et al. 2008; P. Yang et al. 2012; G. Wang et al. 2016; L.-Y. Yang et al. 2016; Hembry & Althoff 2016). Thus there may be up to five species of wasps pollinating the one species of fig (Darwell et al. 2014; Finchet al. 2018), and a single species of wasp may visit several species of figs growing in the one area. Pollinator-sharing between fig species seems to be more common in monoecious neotropical figs than in dioecious palaeotropical figs (Moe et al. 2011, but c.f. G. Wang et al. 2016); it also occurs in some African taxa, where one wasp may reproduce in a number of closely related figs. Lineage duplication, wasp speciation occuring within the one species of fig, also occurs (McLeish & van Noort 2012). Moe and Weiblen (2012) also suggest that in some situations the fig wasp may evolve without there being a corresponding change in the host; the wasp is adapting to its pollinator, rather than vice versa or both changing together Overall, about 30% of Ficus species are pollinated by more than one species of wasp (this figure is likely to be an underestimate), and L.-Y. Yang et al. (2015) found that in dioecious Ficus, where the figure may be over 40%, the wasps pollinating the one species of Ficus may be sister species, and there co-/sympatric speciation is possible, however, in monoecious Ficus around two thirds of the co-pollinators were not sister species. In parallel with this difference, phylogenies of plant and insect in dioecious figs may be largely congruent, less so in monoecious figs (Yang et al. 2015). In dioecious figs, hybridization and gene flow has been reported (Wang et al. 2016). There is clearly an issue with species limits here... Overall the wasps have speciated more than the figs, there being perhaps over 1,000 species of agaonids, although the great majority are undescribed (Cook & Segar 2010; Darwell et al. 2014). Hembry et al. (2014) discuss the fig-fig wasp association from the point of view of the extent to which it represents a coevolutionary situation; see also papers in J. Biogeog. 23(4). 1996, also Plant-Animal Relationships [below] for further details). Asparagaceae-Agavoideae, Ranunculaceae, Phyllanthaceae, Saxifragaceae and Caryophyllaceae have similar interactions between plant and pollinator (see Hembry and Althoff 2016 and Kawakita and Kato 2017f for reviews of diversification and coevolution in these systems).
Obviously timing of diversification of the two partners is important in thinking of this as an example of coevolution, and in view of the variety of crown group ages for Ficus suggested above, note that a recent estimate of the crown group age of a clade made up of Agaonidae and associated galling wasps was only (89-)49(-27) Ma (Peters et al. 2017b: ages for parasitoids, etc., still younger - see below). Other estimates of the age of crown group Ficus, (101.9-)74.9(-60.0) Ma, and that of the fig wasps, (94.9-)75.1(-56.2) Ma, are quite similar to each other (Cruaud et al. 2012b), if different from the dates just mentioned, however, comparing the ages of figs and pollinators at 36 nodes, in eight of these the estimates of the ages of the figs were older, while in the rest, the wasps were older, and the ages were often quite different, which makes thinking of strict coevolution difficult. Volf et al. (2018) suggested that radiation of metalmark choreutid moths, common herbivores on Ficus, occurred ca 70 Ma; this was shortly after the beginning of diversification in Ficus and might reflect sequential coevolution of these moths (Rota et al. 2016 estimate a crown group age - Brenthia versus the rest of the family - of (96-)76(-58) Ma, with much subsequent long distance dispersal). Although larvae of these moths (some adults mimic jumping spiders) are common on Ficus, they also eat a variety of other families - check out Hosts.
Pollination Biology & Seed Dispersal. There are around 800 species of figs, and they are closely associated with perhaps 10,000 or so species of fig wasps (Cook & West 2005), and these latter include pollinators, gallers, inquilines, and parasitoids. Basic details of the association between figs and their agaonid chalcid fig-wasp pollinators (Agaonidae) may be summarized as follows. Female wasps are fertilized by flightless males inside the fig, and in passive pollination, as in section Pharmacosycea, the pollen from staminate flowers becomes passively attached to the wasps as they wander around the inside of the fig. However, in other species females actively pick up pollen from the staminate flowers - these are at least sometimes aggregated around the ostiole - using their coxal combs and store it in thoracic pockets specialized for this purpose; this is active pollination. In figs with active pollination there are fewer male flowers in the syconium than if there is passive pollination. (Whether active or passive pollination is ancestral for Ficus is unknown - Cruaud et al. 2012b; there are possible differences in pollen morphology between passively and actively pollinated flowers - G. Wang et al. 2014). The female wasps leave via exit holes in the wall of the fig that are prepared by the males (e.g. Kjellberg et al. 2001; Cook & Rasplus 2003) and are attracted to receptive figs by a mixture of terpene volatiles (e.g. C. Chen & Song 2008). They enter via the ostiole, having specialised jaws and a head that is shaped to allow them to squeeze between the bracts surrounding the ostiole, although they often lose their wings and antennae in the process (van Noort & Compton 1996). Carpellate flowers in monoecious figs are layered, that is, they have styles of different lengths, and the wasps lay eggs in the carpellate flowers with long styles which thus become galled, the larvae in them developing into the next generation of wasps (Kerdelhué et al. 2000). The life cycle in gynodioecious/dioecious figs follows the same basic principles: "male" figs produce at most few fruits but many wasps, while female figs produce lots of fruits but few if any wasps (see Janzen 1979 for a good early account; Kerdelhué et al. 2000; Cook & Segar 2010). Wasps pollinating dioecious figs have shorter ovipositors than those pollinating monoecious figs; the sterile female flowers in "male" figs all have short styles and produce wasps, while the female flowers in "female" figs have longer styles and so do not have eggs laid in them (Cook & Segar 2010). Pollination of female figs is by deceit, male and female figs usually producing identical scents if flowers in figs of the two kinds open together, however, the scents may differ if the two kinds of figs open at different times (Hossaert-McKey et al. 2016). Indeed, such differences are seen even at the infraspecific level, as in Ficus carica itself. Here only one of the flowering events that occur in male trees happens at the same time as the single flowering event of female trees, and the scent of male figs that open by themselves differs from that of male figs when they open along with female figs, and in the latter case male and female figs have similar scents (Soler et al. 2012).
Stigmas of passively-pollinated Ficus are bilobed and papillate, in actively-pollinated dioecious species the stigmas are tubular, while in the actively-pollinated monoecious species they are more or less bilobed and papillate adaxially (Teixeira et al. 2018). In the latter two groups, at least, the stigmas of separate flowers may become entangled by exudate, stigmatic papillae or stylar hairs, and it is thought that they form a synstigma, functionally analogous to the extragynoecial compitum of some apocarpous taxa (Basso-Alves et al. 2014; Teixeira et al. 2018), although the growth of pollen tubes across this synstigma seems not to have been described (see also Procris - Urticaceae). Interestingly, figs in which there is no pollination by the wasp, although she does lay eggs, can still develop, as do the wasps, although both fig and wasp tend to be smaller than usual (Jandér & Herre 2016).
Since fig development is often more or less synchronized within trees but asynchronous between trees, and within a single fig staminate flowers mature later than carpellate flowers, out-crossing is favoured (Ahmed et al. 2009). Indeed, although oviposition by fig wasps may be staggered, adults tend to hatch at the same time (e.g. Kerdelhué et al. 2000; Lopez-Vaamonde et al. 2001; Jousselin et al. 2003; Jackson 2004a; Kjellberg et al. 2005; Rønsted et al. 2005b, 2008a for references). Agaonid wasps are tiny, and they can be carried by air currents for up to 14 km even in the rainforest, and so the breeding units of monoecious figs in particular may be an order of magnitude larger - covering some 100 square kilometres or more - than those of other plants there (Herre 1996; Nason et al. 1998; Ashton 2014). Even more remarkably, pollen is transported by wasps for distances over 160 km in riparian populations of the monoecious Ficus sycomorus in the Namib desert (Ahmed et al. 2009). In general pollinators of monoecious figs fly further than those of dioecious figs (Harrison & Rasplus 2006). Monoecious figs tend to be large trees with (very) low population densities and wide distributions while dioecious figs are small trees with higher population densities, pioneers in large gaps (Ashton 2014; L.-Y. Yang et al. 2015). The wasps are attracted to the figs by fragrances secreted by glands on the ostiolar bracts or the outside of the fig, depending on the species (Souza et al. 2015; G. Wang et al. 2016 and references), and there are a variety of other glands in figs, some of which may produce phenolics that may protect the fig against overheating.
In figs the achenial fruits are borne on the inside of the fleshy, invaginated inflorescence axis. Figs are a very important and dependable keystone food resource for frugivores, both birds and mammals, in many places in the tropics (e.g. Shanahan et al. 2001), and the diversity of their growth forms means they are encountered throughout the forest. Fig "fruits" are perhaps surprisingly nutritious (Herre et al. 2008 for references), although there is some argument about this (see Fleming 1986; Shanahan et al. 2001) and there is no comparative study of the nutritional content of Old and New World figs (Snow 1981). In at least some communities figs may be especially important and reliable food resources when other plants are not fruiting; whether or not fruits on individual fig trees ripen synchronously, individual species often do not fruit synchronously. "All accounts agree that figs are among the most important foods of specialized frugivores in Africa, southeast Asia, and Australia..." (Snow 1981: p. 9); in the New World, however, specialised frugivores are less prominent on figs. Figs are ecologically very important in both the New (e.g. Cocha Cashu, Peru: Diaz-Martin et al. 2014) and Old (e.g. Borneo) Worlds, although perhaps less so in Africa and India, and they may have considerable local diversity - for example, there are 77 species in Lambir Hills National Park in Sarawak alone (Shanahan et al. 2001; Harrison & Shanahan 2005). The species richness of Ficus is correlated with that of their avian frugivores, particularly specialised frugivores, and the frugivores also select on particular aspects of the morphology of the fig species (Shanahan et al. 2001; Kissling et al. 2007; Herre et al. 2008: see below). Leighton and Leighton (1983) called the relationship between Ficus and its frugivores a keystone mutualism, since the loss of the figs would deplete the populations of animals that dispersed both Ficus and the fruits of other plants. Monoecious figs in Indo-Malesia, even if at low densities, can be very large plants, furthermore, they fruit continuously, individuals producing very large numbers of figs when other canopy trees are not fruiting, so they "provide famine food for the herbivorous vertebrates" (Ashton 2014: p. 359). Similarly, Terborgh (1986: p. 339) observed, "[s]ubtract figs from the ecosystem and one could expect to see it collapse"; in some New World ecosystems figs, less than 1% of the species (12 out of ca 2,000), sustained nearly the entire frugivore community for three months of the year. Janzen (1979) had calculated that seven species of figs on Barro Colorado Island produced 200,000 ± 75,000 figs ha-1/yr - maybe 195 kg dry weight. Kattan and Valenzuela (2013, see also Snow 1981) discuss the arguments pro and con as to whether figs really are keystone species for frugivores.
Figs are commonly dispersed by bats (Muscarella & Fleming 2008) or birds (Snow 1981; see also Fleming 1986). New and Old World bats search for food in different ways and have selected figs with different qualities; overall fig morphology is quite diverse. Bat-dispersed fruits in the New World often tend to be relatively large (>2.5 cm), rather dull, and greenish or yellowish in colour, and they smell (Compton 1996 [a whole series of papers]; Korine et al. 2000; Shanahan et al. 2001; Harrison 2005; Machado et al. 2018). Some 21 species of Artibeus bats (phyllostomids) are the predominant ficivores there. The bats are slow feeders and spit out larger seeds, fibre, etc., but they commonly disperse the tiny fig achenes. Like other bat-dispersed taxa in the New World, including Cecropia (Urticaceae) and Trema (Cannabaceae), particularly in Mexico (Lobova et al. 2009), species of Ficus can be found in early successional communities (Muscarella & Fleming 2008). The altitudinal ranges of the bats and figs are similar (Fleming 1986). In the Old World bat-dispersed fruits are often yellow, etc., and are sometimes quite large (Kalko et al. 1996; Harrison & Shanahan 2005; Lomáscolo et al. 2008, 2010); bat-dispersed figs in Malesia, also dull-coloured, may not smell, and pteropodids (fruit bats) are the dispersers there (Hodgkinson et al. 2003). Figs that are eaten by birds are often small and red, orange or purple, and they do not smell (Ashton 2014 for the Indo-Malesian species), and in America, at least, propagule dispersal by birds may be more effective than that by bats (Machado et al. 2018).
Plant-Animal Interactions. Many other species of chalcid wasps are part of the fig-fig wasp ecosystem. These non-pollinating fig wasps can be gallers, parasitoids of both pollinating and galling wasps, inquilines (species living commensally in figs) or even seed predators. Interestingly, the adults of the different species in the one fig emerge synchronously (Farache et al. 2018 and references). There can be up to 40 species of chalcid wasps associated with a single fig species (Cook & Segar 2010; Cruaud et al. 2011), although the diversity of the fig wasp community is lower in dioecious figs (Kerdelué & Rasplus 1996; see also Cook & Rasplus 2003). Many wasps seem to be specialists, in one study 55% of the wasp species emerging from figs of a host species were found only on that fig (Farache et al. 2018). The parasitoid wasps that parasitize the fig wasps may be of considerable importance in preserving the relationship between the pollinating wasp and fig (Dunn et al. 2008). Larvae of sycophaginae gall wasps produce galls on individual flowers of figs (none are parasitoids), and they may have have moved on to figs in Australia some 50-40 Ma, i.e. they are half the age of Ficus, with subsequent dispersal to other areas (Cruaud et al. 2011). However, Peters et al. (2017b) dated a clade of pollinating and galling wasps to (89-)49(-27) Ma, and of parasitoids and inquilines to a mere (39-)26(-15) Ma; they did not include any Sycophaginae in their study. The phylogenetic diversity of non-pollinating fig wasps is greater in the Old World than the New World (Cook & Segar 2010). Parasitoid wasps may have very large geographic ranges, even larger than those of pollinating wasps (Sutton et al. 2015; see also above).
Another element in this microcosm are the drosophilid flies that in Africa, at least, have a very close association with figs and oviposit either on the stomium or the exit holes made by the male fig wasps (Harry et al. 1996, 1998). For more information on figs and wasps, as well as gallers and parasitioids, see also Kjellberg et al. (2005), the papers in Symbiosis 45, 1-3 (2008), Silvieus et al. (2008), and especially Herre et al. (2008).Herbivores of Ficus in New Guinea include a couple of specialist moth groups, the noctuoid moth Asota, which may chew into the main vein to interrupt the latex flow before eating the rest of the leaf (Compton 1989 and references) and are found on plants with proteases, and metalmark choreutid moths, which can handle species of figs with hairs - these two groups can also tolerate polyphenol oxidative activity and proteases respectively (Volf et al. 2018). Cysteine proteases are known to afford protection against herbivory (Konno et al. 2004).
Genes & Genomes. Chromosome numbers in Dorstenia are very variable (Berg & Hijman 1999); for more on chromosomes in the family, see Oginuma and Tobe (1995).
Chemistry, Morphology, etc. Laticiferous cells elongate and branch and intrude between other cells, the nuclei divide, but cell walls are not formed. Bauer et al. (2014) discuss details of the latex and its coagulation in Ficus benjamina. Ficus spp. differ considerably in the kinds and arrangement of mineral deposits - silica, calcium oxalate, and amorphous calcium carbonate - in their leaf blades, and these seem to be little affected by the light regime of the plant, its age, etc. (Pierantoni et al. 2019). Some species of Dorstenia have small, cauline stipules that do not overlap the petiole.
Zerega and Gardner (2019: p. 262) describe the inflorescences of Castilleae as having "an involucre of multiple layers of involucral bracts", perhaps comparable to the ostiolar bracts of Ficus. The flowers of Parartocarpeae are apparently sunk into the receptacle and lack a perianth, and the receptacular tissue also goes towards making the tissue of the syncarp (Zerega & Gardner 2019); this should be confirmed. Indeed, floral morphology and anatomy needs attention. Leite et al. (2018) described the flowers of five taxa, of which two seem to be distinctly odd. Thus the staminate flower of Brosimum gaudichaudii is described as having an adaxial bracteole while both staminate and carpellate flowers of Clarisia ilicifolia are described as having two lateral sepals; Castilla elastica has staminate flowers that lack a perianth but are each associated with a trilobed bract. For fig/syconium development, see Rauh and Reznik (1951); Basso-Alves et al. (2014) describe the development of flowers in Ficus. Ovule morphology and embryology in Dorstenia need examination (Berg & Hijman 1999). In some taxa integuments are not evident on the side of the ovule adjacent to the funicle, rather, there is a massive pad-like structure called a "bourrelet" or "wulst" (de Granville 1971).
For general information, see Rohwer (1993a), Berg (2001: American taxa), Berg et al. (2005, 2006: Malesian taxa) and Zerega and Gardner (2019); for chemistry, see Hegnauer (1969, 1990), for pollen, see Burn and Mayle (2008) and for embryology, see Johri and Konar (1956: Ficus).
Phylogeny. For the phylogeny of Moraceae, see Datwyler et al. (2003), Datwyler and Weiblen (2004), Gardner et al. (2017) and especially Clement and Weiblen (2009). Some of the old and paraphyletic Moreae with their incurved stamens are now placed in Maclureae, Castilleae are sister to Ficeae, and relationships between the tribes (see above) are on the whole strongly supported (Clement & Weiblen 2009). However, analyses of morphological characters alone provided little resolution, only Ficeae (the one genus!) being well supported, although most Castilleae formed a clade, albeit with very little support (Clement & Weiblen 2009). Zerega et al. (2010) recovered a [Parartocarpus + Hullettia] clade, which was also found by Gardner et al. (2017), although support for its position could be stronger - in other studies this clade is part of Dorstenieae. The position of Maclureae is a little unclear, and they were found to be sister to [Dorstenieae [Castilleae + Ficeae]] in a two gene analysis by Chung et al. (2017), [Artocarpeae + Moreae] forming a separate clade. However, an analysis of 25 species and 333 nuclear genes [Parartocarpus + Hullettia] were found to be sister to [Dorstenieae [Castilleae + Ficeae]] and with strong support, and although support for the clade [Maclureae [Artocarpeae + Moreae]] was rather less, other relationships were strongly supported (Zerega & Gardner 2019).
Zerega et al. (2010) provided a detailed phylogeny of Artocarpeae, which they recircumscribed. Williams et al. (2017) looked at the phylogeny of Artocarpus, and A. altissima may be sister to the rest of the genus. In Dorstenieae, most infrageneric taxa of Dorstenia itself turned out not to be monophyletic in the analysis of Misiewicz and Zerega (2012), interestingly, D. psilurus var. scabra was recovered as sister to the rest of the genus, separated by a ca 20 Ma internode from all other taxa examined - that included D. psilurus var. psilurus... Chung et al. (2017) looked at relationships around Broussonetia and found that the genus was paraphyletic. Ficeae. Cruaud et al. (2012b) found that relationships along the backbone of Ficus were still rather poorly supported, although the American section Pharmacosycea was likely to be sister to the rest of the genus (see also Pederneiras et al. 2015: the hemiepiphytic F. crassivenosa sister to the section, 2018; Bruun-Lund et al. 2017a; Machado et al. 2018 F. nevesiae sister; Q. Zhang et al. 2018: F. tonduzii sister, sect. Pharmocycea paraphyletic). Note that Bruun-Lund et al. (2017a) found that there was conflict between chloroplast and nuclear studies. For relationships in section Americanae, see Machado et al. (2018: F. bonijesulapensis sister to the rest). In subsection Urostigma (Chantarasuwan et al. 2015), the strict consensus tree of the analysis of 60+ morphological and anatomical characters is one gigantic polytomy; this was another of the sections that were para/polyphyletic in the study of Q. Zhang et al. 2018.
Classification. See Clement and Weiblen (2009) for tribes and their delimitation (note the likely position of Treculia); they also discuss one or two problems with generic limits. Pederneiras et al. (2015) discuss the infrageneric classification of Ficus.
Botanical Trivia. The straightening stamens and reflexing tepals of Morus alba are reported to show the fastest movement of any plant parts known, over half the speed of sound (P. E. Taylor et al. 2006).
URTICACEAE Jussieu, nom. cons. - Back to Rosales
Dihydroflavonols?, (furanocoumarins) +; (wood fluoresces); (wood parenchyma not lignified); laticifers (throughout the plant), latex not milky (milky); petiole bundle(s) annular or arcuate; bundle sheath extensions 0; stomata often anisocytic (paracytic, etc.); cystoliths [in lamina, stem] punctiform; lamina base often asymmetric, vernation laterally or vertically conduplicate, venation palmate, trinerved, stipules interpetiolar; P (1-)4, 5(-6), valvate; staminate flowers: anther endothecium 0; carpellate flowers: G 1; ovule basal, ± straight, both integuments often 2 cells across, (protruding into the stylar canal), (inner integument obturator, of several 1-celled thick projections in t.s.), parietal tissue 4-6 cells across, nucellar cap 2-4 cells across; fruit often a nut or achene, straight; seed coat perforated, ± crushed, but various testal/tegmic layers persisting, ?vascularization; endosperm ± copious, (starchy), chalazal haustorium +, embryo straight; chromosomes 0.9-1.6 µm long, protein bodies in nuclei.
54 [list]/2,625 - five groups below. World-wide, but mainly tropical (map: from Frankenberg & Klaus 1980; Hultén & Fries 1986; Fl. Austral. 3. 1989; Fl. N. Am. 3. 1997: ??Arabia, Central Asia). Photo: Shoot, Flower, Fruit.
[Cecropieae + Boehmerieae]: ?
1a. Cecropieae Gaudichaud
Trees to shrubs (lianas); (stilt roots +); laticifers in flowers 0; bundle sheath extensions +; stomata anomocytic; hairs arachnoid, unicellular; cystoliths 0; leaves spiral, lamina palmately compound or -lobed, (venation pinnate - some Coussapoa), stipules intrapetiolar, connate, ± sheathing the stem [open on side of stem opposite leaf]; plant dioecious; inflorescences thickly spicate/capitate, subumbellate/digitate; staminate flowers: filaments straight in bud (not), pistillode usu. 0; carpellate flowers: stigma lingulate/capitate-penicillate/peltate; (endosperm 0), (cotyledons thick, radicle short - Pouruma, Myrianthus); n = 14
4/145: Cecropia (61), Coussapoa (50). African and esp. American tropics (map: Red, see Bonsen & ter Welle 1963; Trop. Afr. Fl. Pl. Ecol. Distr. 5. 2010).
Synonymy: Cecropiaceae C. C. Berg
1b. [Leucosyke + Maoutia]
Shrublets to small trees; cystoliths associated with hair bases only; stipules intrapetiolar, connate, inflorescences capitate; staminate flowers: pistillode woolly (glabrous); carpellate flowers: P (0); stigma ± sessile, penicillate-long papillate; n = ?
1-2/60. China (Taiwan), tropical Southeast Asia and Malesia to Polynesia (map: See above, green).
2. Boehmerieae Gaudichaud
Plant shrub to small tree, herb; leaves often opposite; (stipules 0 - Soleirolia, etc.); staminate flowers: (C 1, A 1 - Forsskaolea, etc.), pistillode often lanate; carpellate flowers: stigma persistent or not; carpellatte flowers: stigma various [sessile-penicillate/filiform/villous]; ovule bistomal [Parietaria]; n = 13-14, 21.
Boehmeria (80), Pipturus (30).
[Elatostemateae + Urticeae]: leaves 2-ranked, (venation pinnate); carpellate flowers: P ± connate (free); achenes asymmetrical.
3. Elatostemateae Gaudichaud
Herbs (shrubs), often ± fleshy; cystoliths linear; leaves opposite, one sometimes much reduced [= nanophyll] - Pilea/spiral, stipules intrapetiolar, connate [Pilea, etc.]; inflorescence with receptacle or not, if yes, usually involucrate; P 2, 3; staminate flowers: pistillode 0 (small); carpellate flowers: C (0), (shorter than ovary), stigma penicillate (capitate - Sarcopilea); fruit explosively ejected by inflexed staminodes; n = 12-14 (16).
Pilea (500-600), Elatostema (570), Elatostematoides (20-40).
4. Urticeae Lamarck & de Candolle
(annual) herbs/shrubs (trees); plant stinging (not); (cork cortical - Urtica); cystoliths (± linear); leaves (spiral/opposite - Urtica), stipules intrapetiolar, connate, (stipules 2, interpetiolar); P 4 (1); staminate flowers: (filaments straight - Poikilospermum), staminodes ; carpellate flowers: (disymmetrical - Urtica), stigma sessile/capitate-penicillate/linear; ovule with inner integument growing into style base [Laportea], nucellus 4-5 cells across, nucellar cap 2-4 cells across; antipodal cells several [Urtica], n = 11-13.
Urtica (63), Dendrocnide (37), Urera (35).
Evolution: Divergence & Distribution. Boehmerieae are known fossil from Mexican and Dominican amber 26-22.5 My; the flowers are 5-merous and the perianth members aare heteromorphic (Poinar et al. 2016b).
Urtica, although a genus of only moderate size, is widely distributed and has many island endemics. Surprisingly, the small annual U. lobulata, from South Africa, is sister to the shrubby New Zealand U. ferox, the clade they form being associated with clades that are basically Eurasian in distribution (Grosse-Veldmann et al. 2016b).
For the evolution of characters in Urticaceae, see the detailed discussion in Z.-Y. Wu et al. (2015); 16/19 characters they examined showed parallelisms and/or reversals, some, like the external morphology of the achene, with as many as 40 of these events. For the evolution of Urticeae and Elatostemateae, see C. Kim et al. (2015a), and of Elatostema and relatives in particular, see Tseng et al. (2018).
Ecology & Physiology. The ant-plant Cecropia is a fast-growing pioneer tree of the Neotropics that dominates the early succession after forest clearing in South America, but the forest soon changes composition - c.f. situations where Vismia (Hypericaceae) is common (Mesquita et al. 2001). Ecologically, it is a New World analogue of Macaranga (Euphorbiaceae).
Pollination Biology & Seed Dispersal. Explosive dispersal of the pollen as the filaments abruptly straightens is common in Urticaceae. The name "artillery plant", used for cultivated species of Pilea, refers to the little puffs of pollen produced when the inflorescence is jogged. For further details of the mechanism of explosive pollination, see above. A synstigma is reported in the inflorescences of Procris (Teixeira et al. 2018) - see also Ficus. Grosse-Veldmann and Weigend (2018) discuss the variety of breeding systems in Urtica, in particular the variety of different ways that staminate and carpellate flowers are arranged in the inflorescences of monoecious species.
In Pilea the achenes are explosively dispersed by the abrupt straightening of the fleshy, inflexed filaments of the staminodes, the mechanism being similar to that involved in pollen dispersal. The phyllostomid bat Artibeus eats Cecropia in Mexico in particular (Lobova et al. 2009 for records). Frugivorous birds of all kinds also favour the genus (Snow 1981; also Charles-Dominique 1986 and other papers in Estrada & Fleming 1986) and it is a prominent component of secondary vegetation in the New World (see also Musanga in Africa). Myxospermy occurs here and elsewhere in the family (Western 2012).
Plant-Animal Interactions. It has been suggested that caterpillars of Nymphalini butterflies have a plesiomorphic association with Urticaceae as food plants (Janz et al. 2001); caterpillars in a clade of Nymphalidae-Heliconiinae-Acraeini utilise members of this family, probably switching from host plants in the Passifloraceae area (Silva-Brandão et al. 2008; see also Nylin & Wahlberg 2008; Wahlberg et al. 2009; Nylin et al. 2014).
About three quarters of the 61 species of Neotropical Cecropia are associated with Azteca and some other ants that live in the stems and eat glycogen-rich food bodies (Müllerian bodies) produced by the plant at the abaxial base of the petiole (Davidson & McKey 1993; for a phylogeny of Cecropia, see Treiber et al. 2016; Gutiérez-Valencia et al. 2017). The age of this aasociation is unclear (c.f. the topology in Chomicki & Renner 2015: fig. S3), although Gutiérez-Valencia et al. 2017: variety of estimates) date it at around (16.7-)11.1, 8.4, 6(-4.3) Ma. Glycogen is uncommon in plants, and Bischof et al. (2013) describe how it is synthesized. Some beetles also eat these food bodies, along with ant eggs, etc. (Jolivet 1991; Longino 1991; Yu & Davidson 1997). One ant may replace another within this association (Davidson & McKey 1993), and the association between plant and ant can break down, especially on islands and at high altitudes (Janzen 1973; Gutiérez-Valencia et al. 2017); Musanga, e.g. M. cecropioides, from Africa, also lacks ants but is otherwise very similar to Cecropia. Some studies suggested that it might be derived from within Cecropia, and its sister species there, perhaps C. sciadophylla, was also not myrmecophilous (Treiber et al. 2016). Although Gutiérez-Valencia et al. (2017) found that the two genera were sister taxa (the position of the related Myrianthus, also African, was unclear), the presence of prostomata, preformed ant entry holes, in the non-myrmecophilous C. sciadophylla, perhaps sister to the rest of the genus, made understanding the evolution of myrmecophily here difficult (Gutiérez-Valencia et al. 2017); extensive co-speciation is unlikely (Davidson & McKey 1993). For chaetothyrialean ascomycete fungi, also involcved in this association, see Vasse et al. (2017). As with species of Macaranga (Euphorbiaceae) in Malesian forests, bacteria living off colony debris are eaten by rhabditid nematodes that may in turn be eaten by ants (Maschwitz et al. 2016).
The parasitoid chalcoid wasps Aximopsis parasitize only Azteca queens, laying their eggs through the entrance to the colony soon after the queen has closed it (Gates & Pérez-Lachaud 2012 and references).
Chemistry, Morphology, etc. Groups of cells in the vascular tissue may be unlignified and the pericyclic sheath may also be late in lignifying; the presence of unlignified apotracheal parenchyma was used to divide the family (minus Cecropiaceae) into two main groups (Bonson & ter Welle 1984); Cecropia et al. have lignified parenchya (Bonson & ter Welle 1983). Leaves of isophyllous Pilea studied by Dengler and Donnelly (1987) has 3:3 nodes, while in the anisophyllous Pellionia the large leaves had 4:3 nodes and the small leaves 1:1 nodes. Variation in stipule position and morphology around Urtica is considerable (Deng et al. 2013); no mention of prophylls... For the morphology and mineral composition of the stinging hairs of four genera of Urticeae examined, see Mustafa et al. (2018b), interestingly, the hairs were quite variable in their mineralization.
Carpellate inflorescences of Zhengyia are borne towards the apex of the flowering stem, staminate inflorescences are basal (Deng et al. 2013). Boehmeria has a fleshy perianth. For the absence of an endothecium, see Staedtler (1923); this character needs more extensive sampling. Although the gynoecium is basically bicarpellate, one carpel is highly reduced (Eckardt 1937) and there is a single style/stigma that shows a great deal of variation especially in Boehmerieae and Urticeae, lthough Elatostateae are almost entirely penicillate (C.-j. Chen (1985). Shamrov (2004) shows the inner integument of Leucosyke becoming much elaborated and functioning as an obturator. The seeds of Dendrocnide may lack holes in the exotesta, and the whole seed coat is relatively well developed, while Kravtsova (2006) found ingrowths in cell walls of both the pericarp and seed coat, observations that should be extended.
See also Miller (1971), Berg (1978: Cecropiaceae), Kubitzki (1993b: Cecropiaceae) and Friis (1993), all general, Hegnauer (1973, 1990: chemistry), Bigalke (1933: cystoliths and hairs), Modilewski (1908) and Fagerlind (1944a: Elatostema, apomixis, ovules quite variable), both embryology, and Kravtsova (2003: seed coat anatomy, 2009: also fruit wall anatomy) for additional information.
Phylogeny. Urticaceae minus Cecropiaceae are paraphyletic (e.g. Sytsma et al. 2000, 2002 - three genes; Monro 2006 - two genes). Datwyler & Weiblen (2004 - one gene) and Zerega et al. (2005) found strong support for Poikilospermum (map above - green) as sister to the rest of the family - [Poikilospermum [Cecropiaceae s. str. [rest of Urticaceae]]], while Chomicki and Renner (2015: fig. S3) grouped Poikilospermum with Cecropia et al., but this was probably a sampling issue. In an extensive seven-gene/three compartment study four main clades were evident: Cecropieae, only moderately supported, were sister to [Leucosyke + Maoutia], while Poikilospermum was part of a well supported clade that includes Urticeae, etc., and this was sister to the speciose Elatostemateae, anf finally Boehmerieae make up most of another clade where Forsskaoleeae and Parietarieae are sister taxa and in turn are sister to the other Boehmerieae (Z.-Y. Wu et al. 2013, see also 2015). Hadiah et al. (2008) had found similar relationships, Poikilospermum being associated with Urtica, etc. (see also C. Kim et al. 2015a). These clades provide a basis for thinking about diversification in the family.
For relationships in Cecropieae, see Gutiérez-Valencia et al. 2017); the position of Myrianthus was unstable. Elatostemateae. For a preliminary phylogenetic study of Elatostema, see Hadiah et al. (2003); Procris might have to be included (see also Hadiah et al. 2008). However, in a more comprehensive analysis Tseng et al. (2012, esp. 2018) found Pellionia to be sister to a clade of Arican species of Elatostema, with Elatostema subgenus Weddellia, and the genera Elatostematoides and Procris successively sisters to that clade. See Monro (2006) for suggestions as to how to proceed with the phylogenetic analysis of the large genus Pilea. Urticeae. Deng et al. (2013) and in particular C. Kim et al. (2015a) discuss relationships around Urtica; Laportea and Urera are not monophyletic, and Hesperocnide (California, Hawaii!) is embedded in Urtica. For a comprehensive phylogeny of Urtica, which has important implications for species limits there, see Grosse-Veldmann et al. (2016b) and Grosse-Veldman and Weigend (2018).
Classification. The four main clades recovered in the phylogeny of Z.-Y. Wu et al. (2013) are recognised as tribes above, except that [Leucosyke + Maoutia], sister to Cecropieae, are separated from that tribe. Wu et al. (2015) suggest that four subfamilies be recognised, and these then divided into tribes. This may be the way to go, but clarification of the phylogeny would first be useful.
The limits of several genera including Boehmeria, Pouzolzia and Urera are particularly problematic. For Elatostema and genera around it, see Tseng et al. (2018), the classification in W.-T. Wang (2014) will need to be reworked.
146 species of Elatostema were recognized in FoC (2003), 278 species by Wang (2014)...