LIGNOPHYTA

True roots +; lateral meristems: cork cambium producing cork abaxially, vascular cambium producing phloem abaxially and xylem adaxially.

EXTANT SEED PLANTS/SPERMATOPHYTA

Plant woody, evergreen; nicotinic acid metabolised to trigonelline, (cyanogenesis via tyrosine pathway); primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignins derived from (some) sinapyl and particularly coniferyl alcohols, thus containing p-hydroxyphenyl and guaiacyl lignin units, (lignins derived from p-coumaryl alcohol, i.e. S [syringyl] lignin units); true roots present, apex multicellular, xylem exarch, and branching endogenous; arbuscular mycorrhizae +; shoot apical meristem multicellular, interface specific plasmodesmatal network; stem with ectophloic eustele, endodermis 0, xylem endarch, branching exogenous; vascular tissue in t.s. discontinuous by interfascicular regions; vascular cambium + [xylem ("wood") differentiating internally, phloem externally]; wood homoxylous, tracheids and rays alone, tracheid/tracheid pits circular, bordered; mature sieve tube/cell lacking functioning nucleus, plastids with starch grains; phloem fibres +; stem cork cambium superficial, root cork cambium deep seated; leaves with single trace from sympodium ["nodes 1:1"]; stomata ?; leaf vascular bundles collateral; leaves megaphyllous [determinancy evolved first, then ad/abaxial symmetry], spiral, simple, lamina with vein density up to 5 mm/mm² [mean for all non-angiosperms 1.8]; axillary buds associated with at most some leaves; prophylls [including bracteoles] two, lateral; plant heterosporous, sporangia eusporangiate, on sporophylls, sporophylls aggregated in indeterminate cones/strobili; true pollen [microspores, i.e. no distal pore for release of gametes] +, grains mono[ana]sulcate, exine and intine homogeneous; ovules unitegmic, crassinucellate, megaspore tetrad tetrahedral, only one megaspore develops, megasporangium indehiscent; male gametophyte development first endo- then exosporic, tube developing from distal end of grain, to ca 2 mm from receptive surface to egg, gametes two, developing after pollination, with cell walls, with many flagellae; female gametophyte endosporic, initially syncytial, walls then surrounding individual nuclei; seeds "large", first cell wall of zygote transverse, embryo straight, endoscopic [suspensor +], short-minute, with morphological dormancy, white, cotyledons 2; plastid transmission maternal; two copies of LEAFY gene, PHY gene duplications [three - [BP [A/N + C/O]] - copies], nrDNA with 5.8S and 5S rDNA in separate clusters; mitochondrial nad1 intron 2 and coxIIi3 intron and trans-spliced introns present.

MAGNOLIOPHYTA

Lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, non-hydrolysable tannins, quercetin and/or kaempferol +, apigenin and/or luteolin scattered, [cyanogenesis in ANITA grade?], S [syringyl] lignin units common, positive Maüle reaction [syringyl:guaiacyl ratio more than 2-2.5:1], and hemicelluloses as xyloglucans; root apical meristem intermediate-open; root vascular tissue oligarch [di- to pentarch], lateral roots arise opposite or immediately to the side of [when diarch] xylem poles; origin of epidermis with no clear pattern [probably from inner layer of root cap], trichoblasts [differentiated root hair-forming cells] 0; shoot apex with tunica-corpus construction, tunica 2-layered; reaction wood ?, with gelatinous fibres; starch grains simple; primary cell wall mostly with pectic polysaccharides, poor in mannans; tracheid:tracheid [end wall] plates with scalariform pitting, wood parenchyma +; sieve tubes enucleate, sieve plate with pores (0.1-)0.5-10< µm across, cytoplasm with P-proteins, cytoplasm not occluding pores of sieve plate, companion cells from same mother cell that gave rise to the sieve tube; sugar transport in phloem passive; nodes unilacunar [1:?]; stomata with ends of guard cells level with pore, paracytic, outer stomatal ledges producing vestibule; leaves petiolate, lamina [formed from the primordial leaf apex], development of venation acropetal, 2ndary veins pinnate, fine venation reticulate, veins (1.7-)4.1(-5.7) mm/mm², endings free; most/all leaves with axillary buds; flowers perfect, pedicellate, polysymmetric, parts spiral [esp. the A], free, numbers unstable, development in general centripetal; P not sharply differentiated, with a single trace, outer members not enclosing the rest of the bud, often smaller than inner members; A many, filament not sharply distinguished from anther, stout, broad, with a single trace, anther introrse, tetrasporangiate, sporangia in two groups of two [dithecal], ± embedded in the filament, with at least outer secondary parietal cells dividing, each theca dehiscing longitudinally by action of hypodermal endothecium, endothecial cells elongated at right angles to long axis of anther; tapetum glandular, binucleate; microspore mother cells in a block, microsporogenesis successive, walls developing by centripetal furrowing; pollen subspherical, tectum continuous or microperforate, ektexine columellar, endexine thin, compact, lamellate only in the apertural regions; nectary 0; G free, several, ascidiate, with postgenital occlusion by secretion, stylulus short, hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, dry [not secretory]; 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 [crassinucellate], nucellar cap?; megasporocyte single, hypodermal, megaspore tetrad linear, functional megaspore chalazal, lacking sporopollenin and cuticle; female gametophyte four-celled [one module, nucleus of egg cell sister to one of the polar nuclei]; P deciduous in fruit; seed exotestal; pollen binucleate at dispersal, trinucleate eventually, germinating in less than 3 hours, pollination siphonogamous, tube elongated, growing at 80-600 µm/hour, with pectic outer wall, callose inner wall and callose plugs, growing between cells, penetration of ovules via micropyle [porogamous] within ca 18 hours, distance to first ovule 1.1.-2.1 mm, tube moves between nucellar cells; double fertilisation +, endosperm diploid, cellular [micropylar and chalazal domains develop diffently, 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 cellular ab initio, minute; germination hypogeal, seedlings/young plants sympodial; Arabidopsis-type telomeres [(TTTAGGG)_n]; whole genome duplication, 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, paleo AP3 and PI genes [paralogous B-class genes] +, with "DEAER" motif, SEP3/LOFSEP and three copies of the PHY gene, [PHYB [PHYA + PHYC]].

Evolution. Possible apomorphies for flowering plants are in bold. Note that the actual level to which many of these features, particularly the more cryptic ones, should be assigned is unclear. This is because some taxa basal to the [magnoliid + monocot + eudicot] group have been surprisingly little studied, there is considerable homoplasy as well as variation within and between families of the ANITA grade in particular for several of these characters, and also because details of relationships among gymnosperms will affect the level at which some of these characters are pegged. For example, if reticulate-perforate pollen is optimized to the next node on the tree (see Friis et al. 2009 for a discussion), it effectively makes the pollen morphology of the common ancestor of all angiosperms ambiguous... For other features such as details of sugar transport in the phloem, their placement on the tree is frankly speculative. Finally, for features such as parietal tissue/a nucellus only one (Nymphaeales) to three cells thick above the embryo sac and a stylar canal lacking an epidermal layer, although plesiomorphous for basal grade angiosperms (Williams 2009), I am unsure where on the tree a thicker nucellus and a stylar epidermal layer are acquired.

NYMPHAEALES [AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: vessels +, elements with elongated scalariform perforation plates; wood fibres +; axial parenchyma diffuse or diffuse-in-aggregates; tectum reticulate-perforate [here?]; ?genome duplication; "DEAER" motif in AP3 and PI genes lost, gaps in these genes.

COMMELINIDS   Back to Main Tree

Unlignified cells walls with UV-fluorescent ferulic and coumaric acids; (vessels in stem and leaves); SiO₂ bodies in leaves; stomata para- or tetracytic, (cuticular waxes as aggregated rodlets [looking like a scallop of butter]); inflorescence bracteate; (P fully bicyclic [= K + C, stamens adnate to corolla/inner whorl]); pollen starchy; embryo short, broad.

Evolution. Divergence & Distribution. The stem group of commelinids is dated to ca 122 million years before present, divergence within it begins ca 120 million years before present (Janssen & Bremer 2004) - or the figures are 107-98, 99-91 (Arecaceae sister to rest) and 94-86 million years before present respectively (Dasypogonaceae sister to remainder: Wikström et al. 2001), or ca 116 million years before present, Arecaceae and Dasypogonaceae diverging almost immediately, and Poales and [Commelinales = Zingiberales] within 4 million years (Bremer 2000b). Magallón and Castillo (2009) estimate ages of ca 128 and 115 million years for relaxed and constrained penalized likelihood datings for stem group Arecales - and they are sister (and with Dasypogonaceae unresolved) to all commelinids.

Ecology & Physiology. Silica, an apomorphy for the commelinids, is an important plant defence, causing mechanical damage to mouthparts of would-be grazers and also having a number of physiological effects. There is discussion of the effects of silica and silica bodies on herbivores under the Poaceae since most of the experimental work on this subject has been carried out on grasses.

The element silicon is important ecologically in other ways. There is a negative correlation between leaf longevity and silicon concentration in plant tissues (Cooke & Leishman 2011b), and hardly surprisingly the latter tends to be high in commelinids as a whole (Hudson et al. 2005).

Plant-Animal Interactions. Despite this defence, larval food plants of the butterflies Nymphalidae-Satyrinae are widely distributed in the commelinids (Ehrlich & Raven 1964; Peña & Wahlberg 2008), as are those of the beetles Chrysomelidae-Hispinae+Cassidinae (Jolivet 1988; Schmitt 1988; Vencl & Morton 1999; Chaboo 2007). Basal clades in Satyrinae feed on BLAs, while monocots, and especially commelinids (and within commelinids, especially Poaceae) are food for larvae of other clades; Amathusiini seem to be the only satyrine that uses a variety of non-commelinid monocot hosts (Peña & Wahlberg 2008). Unfortunately, the sister group of Satyrinae remains unclear (Heikkilä et al. 2011). 14/39 tribes of Hispinae+Cassidinae for which there is at least some host plant data for their larvae are found on commelinids, 26/39 on some monocot or other (Chaboo 2007); the beetle larvae eat between the veins. Larvae are also found on Boraginaceae, Solanaceae, Convolvulaceae and Asteraceae, in particular, among the core eudicots - asterids seem to be particularly favoured. However, it is unclear if Criocerinae are in a clade immediately related to Hispinae and related monocot-eating beetles, or not (check Chaboo 2007; cf. Wilf et al. 2000 and Gómez-Zurita et al. 2007).

Genes & Genomes. The rate of molecular evolution in commelinids is generally high, ca 0.003 substitutions/site/million years (Smith & Donoghue 2008). However, for some genes like ndhF, at least, the rate of molecular evolution is similar to that in Asparagales, etc. (Givnish et al. 2006). On the other hand, although genes in all three genomic compartments apparently evolve slowly in Arecaceae (Wilson et al. 1990; Baker et al. 2000a, 2000b), the rate seems not that much less than in a number of other monocots, especially monocots other than commelinids (S. W. Graham et al. 2006); was there an increase in the rate of molecular change within some commelinids, some Poales being spectacular examples?

Chemistry, Morphology, etc. Silicon concentrations in tissues of commelinids are generally high, although less so in groups that do not have SiO₂ bodies, although even there they are not always high (Ma & Takahashi 2002; Hudson et al. 2005). Lignins from Poaceae and Arecaceae (and elsewhere?) have p-coumaryl alcohol as well as coniferyl and sinapyl monomers (Seigler 1998). For the chemistry of the distinctive epicuticular waxes scattered in this area of the monocots (Barthlott & Fröhlich 1983), see Meusel et al. (1994).

Although vessels in the stem and leaves are common (Wagner 1977), it may well be incorrect to treat this as a synapomorphy. For floral development, see Endress (1995b) in part. In those few commelinids whose floral developmental genetics has been studied in detail, expression of the B-class gene orthogue of PISTILLATA seems to be restricted to the stamens/staminode and petals (Adam et al. 2007); this may be connected with the more fully bicyclic nature of the perianth found in many members of this clade. In some of the few other monocots studied, development may be somewhat different. Starch-containing pollen is common, but has not been found in Hanguanaceae or Dasypogonaceae (only one species of the latter examined) and in some species of Haemodoraceae, Bromeliaceae, etc. Broad embryos may be a synapomorphy at about this level.

Some morphological information about the commelinids is summarized by Givnish et al. (1999).

Phylogeny. Commelinids are well supported in molecular studies (e.g. S. W. Graham et al. 2006, and references), and they have morphological support as well, but relationships between the main groups within tthem are still somewhat unclear. Hilu et al. (2003: matK) suggested that Poales may be sister to other commelinids, but the posterior probabilities were low. [Commelinales + Zingiberales] do seem to be a nore or less well supported group (Chase et al. 2006; Givnish et al. 2006, 2010b; Soltis et al. 2007a; Qiu et al. 2010 - mitochondrial genes, Poales sister to this clade). Arecales also appear as sister to Poales in some analyses (e.g. S. W. Graham et al. 2006; Givnish et al. 2010b, maximum parsimony), but with very weak support, or support for groupings of major clades may in general be weak (Chase et al. 2000a; Soltis et al. 2007a). Soltis et al. (2011) found Poales to be sister to other commelinids examined (Kingia, etc. not included), although support was weak, as was that for the position of Arecales as sister to remaining commelinids. See also Commelinales, Zingiberales, and Poales for further discussion of relationships.

Phylogeny. The position of Dasypogonaceae remains unclear. Neyland (2002b: 26s rDNA) found that Dasypogonaceae were strongly associated with Restionaceae and other families (Poales), but this particular relationship has not been suggested in analyses of other molecular data, nor does it appear in morphological analyses. However, other work using multi-gene data sets was not linking Dasypogonaceae with Arecales, even if where they ended up had no strong support (see Givnish et al. 2006 and Chase et al. 2006 - near Poales; S. W. Graham et al. 2006 - near [Commelinales + Zingiberales]). More recently, Givnish et al. (2011b) and Davis et al. (2011 [evidence from structural mutations], see also Barrett & Davis 2011) have found some support in maximum likelihood analyses of plastomes for a position sister to Arecaceae, perhaps consistent with what morphological data there is, although in a maximum parsimony analysis they were placed sister to [Commelinales + Zingiberales], if with little support. Changes in relationships may well occur, and so the topology in this part of the tree is only tentative.

Classification. Givnish et al. (1999) erected a classification of four superorders and 10 orders for the commelinids based on a rbcL phylogeny, A.P.G. (1999, 2003) has recognised many fewer orders. These are generally well supported clades with stable contents.

Unplaced:  Back to Main Tree

DASYPOGONACEAE Dumortier

Plant non-mycorrhizal; rhizomatous or arborescent, (extensive primary thickening +); vessels only in roots; 2 peripheral phloem strands in foliar bundles; leaves spiral, (serrulate), sheath well developed, bases persisting; P dry; septal nectaries +; ovule 1/carpel, ascending, epitropous[?], micropyle bistomal (zig-zag), outer integument 6-8 cells across, parietal tissue ca 2 cells across, nucellar cap ca 2 cells across, suprachalazal tissue massive; seeds rounded, testa pale yellow; endosperm type?

4[list]/16. West Australia, Victoria. [Photo - Habit, Flowers].

[Dasypogon + Calectasia]

Hairs branched; (chelidonic acid + - Dasypogon); raphides only in flowers; SiO₂ epidermal; stomatal accessory cell ontogeny odd; leaf bundle girders 0; inflorescence capitate, flowers in clusters or single; T, or outer whorl only, connate, floral tube short; A adnate to base of T, (anthers dehiscing by pores - Calectasia); massive storage nucellus [below embryo sac]; fruit indehiscent; tegmen collapsing; n = 7, 9; cotyledon not photosynthetic, mesocotyl and coleoptile +.

2/14. S.W. Australia, Victoria (map: from Barrett & Dixon 2001; FloraBase 2004).

Synonymy: Calectasiaceae Endlicher

[Kingia + Baxteria]

Plant with epicortical roots [Kingia]; raphides 0; leaf bundle girders + [originating in mesophyll]; inflorescence capitate or single-flowered [Baxteria], surrounded by bracts, stalk bracteate; T (large - Baxteria) free; A ± adnate to base; pollen extended sulcate-unipantocolpate; fruit indehiscent or explosively septifragal [Baxteria]; storage nucellus?; n = 7; seedling?

2/2. S.W. Australia (map: from FloraBase 2004).

Synonymy: Baxteriaceae Takhtajan, Kingiaceae Schnizlein

Evolution. Divergence & Distribution. Stem group Dasypogonaceae are dated to ca 119 million years before present, divergence within crown group Dasypogonaceae to ca 100 million years before present (Janssen & Bremer 2004: they place Dasypogonaceae rather near the base of the commelinids). Magallón and Castillo (2009) estimate ages of ca 128 and 115 million years for relaxed and constrained penalized likelihood datings for stem group Dasypogonaceae. Dasypogon and Calectasia may have diverged 49-41 million years before present (Wikström et al. 2001).

Chemistry, Morphology, etc. Calectasia has a 1-locular ovary; some species have stilt roots. For Calectasia, see Barrett and Dixon (2001). In Kingia the apical meristem is depressed, as in Arecaceae, and the plant is also monopodial; adventitious roots grow down to the ground in persistent sheathing leaf bases.

Information is taken from Chanda and Ghosh (1976: pollen), Rudall (1994: embryology), and Clifford et al. (1998b).

Phylogeny. See Rudall and Chase (1996) for the dismemberment of the old Xanthorrhoeaceae and the relationships of the genera of Dasypogonaceae.

Previous Relationships. Dasypogonaceae have often been linked with other similar-appearing xeromorphic monocots from Australia such as Xanthorrhoeaceae and Laxmanniaceae (previously Lomandraceae), as in Takhtajan (1997); the two latter families are in Asparagales.

Classification. The name Dasypogonales Doweld is available for this clade if needed.

ARECALES Bromhead  Main Tree, Synapomorphies.

Plant woody, unbranched, growth monopodial; vessels also in stem and leaf; cuticular waxes as aggregated rodlets, stomata tetracytic; leaves spiral, massive, vernation reduplicate-plicate, pinnately pseudocompound, petiolate, with closed sheath; flowers ± sessile; septal nectaries +; ovule 1/carpel, apotropous, sessile, attachment broad.

1 family, 189 genera, 2361 species.

Evolution. See below, after the family.

ARECACEAE Berchtold & J. Presl, nom. cons.//Palmae Jussieu, nom. cons. et nom. alt.   Back to Arecales

Flavonoid sulphates abundant; roots lacking real elongation zone, with radially elongated air spaces; sieve tubes with simple sieve plates; endodermal cells with O-shaped thickenings; cellulose fibrils in the outer epidermal walls randomly oriented, SiO₂ bodies spherical, often spiny-verrucate, esp. associated with fibre strands or vascular bundles, epidermal cells rectangular, hypodermal cells rectangular, longitudinally elongate; stomatal subsidiary cells with oblique cell divisions; fibre bundles both free in mesophyll and attached to epidermes, sheaths of transverse veins fibrous; plant often monoecious; inflorescences with bicarinate prophyll, prophylls lateral [on branches, hence ultimate units are cincinni]; staminate flowers: A basifixed, (many, but basically trimerous); pistillode ± +; pistillate flowers: staminode +; G 1-4 [2-10]; outer integument 8+ cells across, inner integument 2-3(-7 cells across - Cocos), parietal tissue (0)1-5(-6) cells across; (postament +), suprachalazal area ± massive; micropylar embryo sac haustorium +; fruit a (dry) berry or drupe; seed 1(-3), rounded; testa usually with two outer layers thickened, (basal portion vascularized); micropylar endosperm haustorium +, endosperm with hemicellulose [mannans], thick-walled; cotyledon not photosynthetic, collar short (with roots), primary root strong, branched.

183[list]/2361 - five groups below. Humid tropics and subtropics (warm temperate), Africa is relatively depauperate. [Photo - Flowers, Fruits.]

1. Calamoideae Beilschmied

Plant spiny; sustained primary growth slight-0; root periderm 0; (endodermal cell walls barely thickened - Eugeissona); epidermal cells rectangular, anticlinal walls sinuous, (SiO₂ bodies minute, disciform - Eugeissona); adaxial subepidermal bundles of fibres +, parenchyma cells near protoxylem inflated (not), longitudinal veins bridging to adaxial epidermis via vertically-elongated sclereids, lateral bundles adaxial to longitudinal bundles, adaxial non-vascular fibres subepidermal; internodes usu. well-developed; (leaves palmate); (inflorescence axes adnate to the internode above, or to sheath of the leaf of the next node); breeding system various; flowers in dyads; C valvate, connate (free); (pollen equatorially disulcate - Calameae); ovule basal, epitropous[?], [funicle twisted], style branched; fruit covered by reflexed scales, endocarp thin (thick - Eugeissona); seeds 1-3, sarcotesta usually thick; n = 13, 14.

21/: Calamus (400), Daemonorops (115). Tropical, but esp. Sri Lanka to West Samoa and Fiji (map: from Uhl & Dransfield 1987).

Synonymy: Calamaceae Perleb, Lepidocaryaceae Martius, Sagaceae Schultz-Schultzenstein

[Nypoideae [Coryphoideae, Ceroxyloideae, Arecoideae]]: sustained primary growth +; root periderm +; anticlinal epidermal walls ± straight, adaxial subepidermal fibres 0.

2. Nypoideae Griffith

Stem dichotomously branched; endodermal cell walls barely thickened; epidermis with hydathodes, epidermal cells hexagonal to spindle-shaped, guard cells with several ledges [in t.s.], SiO₂ bodies small, hat-shaped; hypodermal cells several layered, lignified, hexagonal, transversely elongate, veins bridging to epidermis via vertically-elongated sclereids, sheaths of transverse veins sclereidal, veins sinuous, irregular; inflorescence axes adnate to the internode above, with staminate a spike, carpellate a head; C free; staminate flowers: P undifferentiated; A 3, opposite outer P, connate, extrorse; pollen with encircling sulcus; pistillode 0; carpellate flowers: staminodes 0; G 3 (4), margins conduplicate, placentation laminar to submarginal; ovule [position?], outer integument ca 10 cells across; n = ?17.

1/1: Nypa fruticans. Malesia (Bengal to Queensland) (map: current distribution in red, from Uhl & Dransfield 1987; fossil records from other places outside this area in blue, from Plaziat et al. 2001).

Synonymy: Nypaceae Le Maout & Decaisne

[Coryphoideae [Ceroxyloideae + Arecoideae]]: sieve tube with compound sieve plates; endodermal cell walls with U-shaped thickenings (thickened all around); (leaf veins bridging to epidermis by fibres); microsporogenesis simultaneous; (postament +).

3. Coryphoideae Burnett

(Stem branched - e.g. Caryota); septate fibres +; no fibre bundles free in mesophyll, longitudinal bundles with ad/abaxially elongated bridging sclereids, transverse bundles with broad sheath of fibres, adaxial vein rib with 5 or more independent vascular bundles; leaves palmate or costapalmate (pinnate), induplicate; inflorescence various, (terminal; adnate to the internode above; plant monoecious - Caryotinae; flowers in triads); C often valvate, connate (free); microsporocyte with callose ring [not Caryota, Bismarckia]; G free, (1), or postgenitally connate by style, or style present, with 3 [Coryphinae] or 1 [Sabalinae] stylar canals, or style 0 [Caryoteae].

45/ca 500: Coccothrinax (50). Pantropical (to warm temperate), fewer in South America (map: from Uhl & Dransfield 1987).

Synonymy: Borassaceae Schultz-Schultzenstein, Coryphaceae Schultz-Schultzenstein, Phoenicaceae Burnett, Sabalaceae Schultz-Schultzenstein

[Ceroxyloideae + Arecoideae]: petiole bundles arranged in one or more Vs (scattered); sheaths of transverse veins sclereidal, veins sinuous, irregular, epidermal cells hexagonal to spindle-shaped.

4. Ceroxyloideae Drude

Flowers solitary along the rhachis, (K and C elongate); (A numerous, not trimerous, centrifugal - Phytelepheae); (seeds more than 3).

8/42. Mostly Central and W. South America, also N.E. Australia, Madagascar, Florida and the Antilles (map: from Uhl & Dransfield 1987).

Synonymy: Phytelephantceae Perleb

5. Arecoideae Beilschmied

Stem with crownshaft [formed by elongated leaf sheaths]; (SiO₂ bodies hat-shaped); hypodermal cells hexagonal, transversely elongate; plant usually monoecious; inflorescence with prophyll and bract(s); (plant dioecious); inflorescence cymose, flowers in triads [central (upper) flower carpellate, lateral flowers staminate] or acervuli [flowers in two vertical rows]; inflorescences monopodial and flowers single; (1 G fertile), separate styles + (style +, short or long); n = 16.

112/ : Bactris (240), Dypsis (140), Pinanga (120), Chamaedorea (110), Geonoma (75), Desmoncus (65<), Areca (60), Astrocaryum (50). Pantropical, the most diverse subfamily in South America (map: from Uhl & Dransfield 1987).

Synonymy: Acristaceae O. F. Cook, Ceroxylaceae Vines, Chamaedoraceae O. F. Cook, Cocosaceae Schultz-Schultzenstein, Geonomataceae O. F. Cook, Iriarteaceae O. F. Cook & Doyle, Malortieaceae O. F. Cook, Manicariaceae O. F. Cook, Moreniaceae O. F. Cook, Pseudophoenicaceae O. F. Cook, Synechanthaceae O. F. Cook

• Arecaceae can be recognised by their woody stems, large, tough, petiolate leaves with plicate and often apparently compound blades, axillary inflorescences (but Corypha, etc.!) with numerous flowers, and 1-seeded fruits. Cyclanthaceae can be similar vegetatively, but their petioles are usually less woody and the leaf never has a hastula, an adaxial flap-like structure at the apex of the petiole.

Evolution. Divergence & Distribution. Stem group Arecaceae are dated to ca 120 million years before present, divergence within the crown group to ca 110 million years before present (Janssen & Bremer 2004), or the dates are 99-91 and 73-63 million years before present respectively (Wikström et al. 2001). Magallón and Castillo (2009) estimate ages of ca 128 and 115 million years for relaxed and constrained penalized likelihood datings for stem group Arecales. Fossil material of the family may be up to ca 93 million years old (Pan et al. 2006; Harley 2006), and palm pollen was abundant in tropical Gondwanan areas during the later Cretaceous (Nichols & Johnson 2008). Palm leaves, pollen and/or wood are quite common and widely distributed in the later Cretaceous when global temperatures were warmer (Burnham & Johnson 2004), even in Africa and India where palms are not very diverse today; in Africa palms became less common at the beginning of the Tertiary and again at the end of the Eocene ca 34 million years ago (Pan et al. 2006; Harley 2006 for a summary of the fossil record).

It has recently been suggested that palms have diversified at a constant rate from their evolution in the middle of the Cretaceous ca 100 million years or more ago in Laurasia until ca 24 million years ago in the Neogene (Couvreur et al. 2011b, esp. c), the K/T boundary passing unmarked - almost a Hubbellian universe. Palms then serve as markers for tropical rainforest - or perhaps merely a tropical rain forest-like biome (Couvreur et al. 2011b). Certainly, present-day palms are very susceptible to frost, most having only a single vegetative meristem yet being unable to produce replacement meristems if the first is killed. They are usually found in places where the mean annual temperature is more than 10°, mean temperatures in the coldest month are more than 5°, and the coldest temperature does not dip below -10° (Greenwood & Wing 1995; see also Couvreur et al. 2011c).

Material (leaf, stem, fruit) from rocks in Texas of Cretaceous-Campanian age some 77 million years old has been identified as the modern genus Sabal; young dinosaurs may have eaten their fruits (Manchester et al. 2010a). Lodoicea is currently restricted to the Seychelles, although its fruits are widely distributed by the sea; ocean crust separating India and the Seychelles date to ca 63.4 million years old (Collier et al. 2008), so either Lodoicea is that old, or it has somehow moved onto these islands. Distinctive Nypa fossils are known from the early Tertiary when the genus seems to have had a distribution that was more or less world-wide; fossils are known from Tasmania, England (the London Clay flora), both Americas, etc. (Plaziat et al. 2001 - see map above). Finally, Hartwich et al. (2010) found fossil calamoid palm leaves and fruits in Late Eocene rocks on the very southern part of New Zealand; members of the subfamily currently grow in eastern Australia, so this is a rather less dramatic range difference than for Nypa.

Not only are Arecaceae the largest clade of woody monocots, their seeds are absolutely large when compared with those of all other angiosperms (Linkies et al. 2010). Despite the size of the palm plant and the size of the fruit, dispersal rather than vicariance is increasingly frequently being invoked to explain many apects of the present distribution of the family. The scattered and apparently ancient Gondwanan distribution of Ceroxyloideae is probably best explained by several mid-Tertiary trans-oceanic dispersal events (Trénel et al. 2007), while species of Hyophorbe (Arecoideae-Chamaedoreeae) are disjunct on the Mascarenes, and the genus may have radiated there on islands that are now submerged, hopping from island to island (Cuenca et al. 2007); some Myrtaceae, Begoniaceae, and Sapotaceae may show similar island-hopping behaviour. The diversity and diversification of palms in the New World, at least, has been linked to the persistence of the relatively warm and wet areas that they favour (Svenning et al. 2008), Arecoideae-Bactridineae diverged there at the end of the Eocene (Eiserhardt et al. 2011a), while Couvreur et al. (2011b) suggest that the stem age of Calamus, currently with some 400 or more species, is a mere 24 million years ago. Roncal et al. (2008) explored the biogeography of Antillean palms and Roncal et al. (2010) examined the biogeography of the mostly understorey Geonomateae; divergence of the crown group began in the Oligocene, speciation is older than expected from a Quaternary refugium theory, and again, there seems to have been considerable dispersal.

Ecology & Physiology. Eiserhardt et al. (2011b) think about the distribution of palms world-wide in the context of ecological determinants both of geography and diversity. The suspects are very much as one might expect, with climate having a major effect on broad-scale patterns and dispersal on patterns at all scales. Arecaceae are another example of the eco-morphological combination of shaded conditions, net-veined leaves and fleshy fruits that has evolved several times in monocots (Givnish et al. 2005, 2006b).

Palms are very susceptible to frost, most having only a single vegetative meristem yet being unable to produce replacement meristems if the first is killed. Hence they are usually found in places where the mean annual temperature is more than 10°, mean temperatures in the coldest month are more than 5°, and the coldest temperature does not dip below -10° (Greenwood & Wing 1995; see also Couvreur et al. 2011c). However, how the vascular system remains functional over long periods of time is unknow. Vessels in Rhapis excelsa are quite resistant to embolism, but what goes on in the very long vessels of some calamoid palms - some over 0.5 mm wide, to almost 4 m long, and spanning (8-)13(-18) internodes - is unclear (Sperry 1986; Fisher et al. 2002; Tomlinson 2006b).

Palms are very conspicuous elements of some vegetation types. Nypa is a dominant element of some mangrove habitats. It prefers less saline conditions than many other mangrove plants and is found along rivers up to the limit of tidal influence; although now Indo-Malesian, its past distribution was almost world-wide in suitable climates (see above). For the evolution of the mangrove habitat, see Rhizophoraceae>

Plant-Animal Interactions. Satyrinae-Morphini butterfly larvae may be found on Arecaceae, along with larvae of the beetle Hispinae-Cassidinae; these latter can be serious pests of oil palms and other commercial or ornamental palms (Chaboo 2007). Stem Bruchinae - the highly speciose seed beetles, now found mostly on Fabaceae - may be 85-82.6 million years old (age spread far greater) and have eaten the seeds of Arecaceae (Kergoat et al. 2011 and references).

Floral Biology & Seed Dispersal. Pollination is predominantly by insects, whether beetles (mainly Nitidulae and Cuculionidae-Derelomini [weevils]), bees, especially Halictidae (sweat bees) and Meliponini (stingless bees), and flies, which may visit especially understorey palms (Henderson 1986, 2002; Barfod et al. 2011). There are suggestions of mimicry of male by female flowers in Geonoma (Stauffer et al. 2002 and references), but presentation of the nectar of both flower types in a similar fashion (cf. Meliaceae) may be another explanation. Dufaÿ et al. (2003) found that it was volatiles produced by the leaves of Chamaerops humilis that attracted its weevil pollinator. Thermogenesis has been detected in the flowers of some Arecaceae (Seymour 2001). There is no clear correlation of pollen morphology with pollinator (Sannier et al. 2009). The speciose New World Chamaedoreeae (Arecoideae) are characterised by raphides in the flowers and in Chamaedorea these are particularly common in the perianth and gynoecium; there are other potentially protective structures in the flowers (Askgaard et al. 2008).

Seed size in Arecaceae seems to have undergone a notable increase, probably associated with the adoption of the tree habit by the clade (Moles et al. 2005a); dispersal is primarily by animals, although Cocos nucifera, dispersed by sea currents, is a notable exception (Henderson 2002). The family is another monocot group with net-veined leaves and fleshy fruits and that can tolerate shade (Givnish et al. 2005, 2006b).

Vegetative Variation. In general, seedling morphology is very variable within Arecaceae (Henderson 2002, 2006; Tillich 2007). It is particularly notable that in palms with aerial stems there is usually a period of establishment growth of the seedlings, and this may last up to 50 years (references in Henderson 2002). During this time the apical meristem becomes gradually larger, as does the width of the axis it produces, and only when it has reached adult size does elongation growth of the trunk occur. With some exceptions, the size of the apical meristem and hence the width of the trunk remains constant for rest of the life of the palm. However, Iriarteeae (Arecoideae) are an exception to this pattern. Here the apical meristem in the above-ground stem becomes gradually larger, and so the trunk becomes gradually stouter and is narrowly obconical at the base. Such a stem is obviously highly unstable, but massive prop roots develop from the lower part of the trunk and stabilise it. In the older plant the base of the stem rots away, the plant then depending entirely on its prop roots.

Arecaceae have the oldest functioning xylem elements and sieve tubes to be found in seed plants. Since the oldest palm is hundreds of years old and there is no secondary thickening, the vascular tissue at the base of the stem must remain active for the whole life of the plant. However, old palm stem are not inert. Thus the walls of vascular fibres continue to thicken, so increasing stem stiffness as the palm tree grows bigger (Tomlinson et al. 2011). Tomlinson et al. (2009, see also 2011) have found that ground tissues in both stem and root may remain undifferentiated for some time and undergo limited mitosis and/or cell expansion, the diffuse secondary thickening of Tomlinson (1961c) and the sustained primary growth of Tomlinson et al. (2011 - this is the preferred term); their ability to remain metabolically active may also help explain the functional longevity of palm vascular tissue. (It has been suggested that at least some palms have monocot-type secondary thickening [Angyalossy et al. 2008]; this may refer to this limited activity in the ground tissue.) Note that the longevity of seed plant cells in general would repay investigation - some xylem parenchyma cells in broad-leaved angiosperms may also remain metabolically active for 200 years or so (Spicer & Holbrook 2007). Parthasarathy (1974) described phloem development while Tomlinson (2006b) discussed xylem function in the context of the length of the stem (Calamoideae were the focus), although the age of the stem did not shape the discussion.

"Leaflets" of induplicate leaves are V-shaped in cross section, those of reduplicate leaves are inverted V-shaped. "Leaflets" of induplicate leaves are V-shaped in cross section, those of reduplicate leaves are inverted V-shaped. Despite appearances, the leaves of all palms are simple. The deep lobes in simple palm leaves, and the leaflets in apparently compound leaves, are commonly thought of as being the result of cell death. However, in a recent detailed study of Chamaedorea species, it was found that the process is rather more like abscission (Nowak et al. 2007, 2008), although nothing (apart, sometimes, from the lamina margin in other genera) falls off. The parts that will separate first become thin, then split apart; tissue at the zone of separation may protect the rest of the blade because it becomes lignified or suberised, or covered by a cuticle that develops. Details of this process differ even between closely-related species depending on the timing of events (Nowak et al. 2007, 2008). In a number of palms thin "reins" can be found hanging down from the sides of the leaves; these represent the lamina margins of the originally simple blade. Fibrous filaments occuring between the leaflets is other evidence for the originally simple nature of the leaf. Given the distinctive development of these "compound" leaves, it is not surprising to find that KNOX genes are not involved in their development, although they are in conventional compound leaves of broad-leaved angiosperms (Nowak et al. 2011).

Fibers found at the bases of the leaves are produced by the decay of the sheaths, while the spines found on so many palms are produced in various ways: modified leaflets (Phoenix), adventitious roots (Crysophila, but relatively uncommon), partly detaching outer parts of the stem that become erect, etc. (Tomlinson 1962b; Tomlinson et al. 2011).

Most Calamoideae (the rattans) and some Arecoideae (Desmoncos), are climbers, either by the aid of a long, hook-bearing apical portion of the leaf, the cirrus, and also, in the case of Calamus, etc., a very much modified long and very thin inflorescence axis with recurved spines, the flagellum, that is adnate to the sheath of the leaf at the node above. Although these climbing aids are remarkably effective (Calamus is sometimes called the lawyer vine, because once you are caught by the the flagellum, it can be very difficult to get free), they eventually fall off with the leaves, and the stems, which can reach lengths of up to some 200 m, then tend to sag (Isnard & Rowe 2008 for details). Calamoid palms are a very important liane group in the South East Asian forests (Gentry 1991).

Dichotomous branching is scattered in the family, having first been recorded from Hyphaene thebaica by Schoute in 1909 (e.g. Fisher 1974 and references).

Genes & Genomes. The rate of molecular evolution in Arecaceae is rather low, as might be expected from a woody plant with a relatively long generation time, and is ca 0.0014 substitutions/site/million years; this is interpreted as representing a reduction in the rate of molecular evolution (Smith & Donoghue 2008; see Gaut et al. 1996 for a comparison between Poaceae and Arecaceae).

Economic Importance. Cocos nucifera Arecoideae - Cocoseae). There is much debate as to the place of origin of the genus, Gunn (2004) suggesting that it it might be sister to the New World Parajubaea and at least 22 million years old, while Meerow et al. (2009a, esp. b) found a sister relationship with the New World Syagrus from which it diverged (39.5-)34.9(-20.7) million years ago, with crown group divergence beginning ca 11 million years ago (Merrow et al. 2009b: 95% HPD limits). On the other hand, Kapgate (2009) found fruits in the Deccan Intertrappean Beds that are of Late Cretaceous - Early Tertiary age ca 65.5 million years before present (see also Gómez-Navarro et al. 2009 for additional references) and Gómez-Navarro et al. (2009) found fruits that they compared with Cocos from northern Colombia that are perhaps a little younger - about 58 million years old... Something seems wrong. Domestication and cultivation seems to have occured independently in southern India and the Malesian archipelago (Gunn et al. 2011).

Elaeis guineensis (also Cocoseae), the oil palm, is a major tropical plantation crop; its cultivation has been responsible for particularly notable deforestation...

Chemistry, Morphology, etc. Horn et al. (2008, 2010a, esp. 2009b) and Tomlinson et al. (2011) look at various aspects of lamina anatomy in the context of the phylogeny of the family; this has in part been integrated above, but there is widespread homoplasy in the characters, so Horn et al. (2009b) and Tomlinson et al. (2011) should be consulted for details, as well as for the functional implications of their findings. Tomlinson et al. (2011) provide a definitive anatomical survey of the family. According to Arber (1925), the vascular bundles are not amphivasal.

For variation in details of the inflorescence units in Arecoideae-Chamaedoreae, where acervuli, modified largely ebracteate cincinni with sessile flowers, occur, see Uhl and Moore (1978), Cuenca et al. (2009), and Ortega-Chávez & Stauffer 2011). The flower in general (e.g. Rudall et al. 2003b; Uhl & Moore 1971) and pollen in particular (see Harley 1999b; Harley & Baker 2001) is remarkably variable. The stamens are never adnate to the corolla/inner tepals in staminate flowers, although in carpellate flowers of Roystonea the corolla has a broad staminal cup at the base, and in carpellate flowers of Geonomeae (Arecoideae), both the calyx and corolla are connate and the stamens are adnate to the corolla (Stauffer & Endress 2003); the style there is more or less gynobasic. Nadot et al. (2011) map androecial evolution on a phylogenetic tree; developmental details of polyandrous flowers vary considerably in the family, but apart from Phytelepheae, the androecium is basically trimerous. Microsporogenesis is simultaneous in some Coryphoideae and Arecoideae (Harley 1999a; Sannier et al. 2006). Variaton in gynoecial development is especially pronounced in Coryphoideae, where all intermediates between syncarpous and apocarpous gynoecia are to be found, and there is sometimes only a single carpel; all told, apocarpy has probably evolved four time within Arecaceae (Rudall et al. 2011b). Cocos may have a bisporic 8-nucleate embryo sac and ovules that lack parietal tissue (Robertson 1976). In Voaniola n = 298 or more.

Students of palms are fortunate in having a series of major works devoted to the family; these include von Martius's (and collaborators) magnificent Historia naturalis palmarum (1823-1850 - see also Martius 2010) - surely one of the greatest botanical publications, Corner (1966), Uhl and Dransfield (1987), Henderson (2002), Dransfield et al. (2008) and Tomlinson et al. (2011).

Additional information may be found in Uhl (1972: Nypa), Tomlinson (1970: vascular organization in the stem), Tomlinson (1974: stomatal development), Uhl and Moore (1971), Moore (1973), Zona (1997: general, esp. south east U.S.A.), Seubert (1998 and references: root anatomy), Dransfield and Uhl (1998: general), Harley and Dransfield (2003: triporate pollen), Zona (2004: embryo raphides), Prychid et al. (2004) and Piperno (2006), both SiO₂ bodies/phytoliths, Tomlinson (2006a: general), Bjorholm et al. (2006: patterns of subfamilial diversity in neotropical subfamilies, the Antilles excluded), Henderson (2006: very detailed descriptions of germination, not integrated with phylogeny), Gunawardena and Dengler (2006: leaf development), Sannier et al. (2007: microsporogenesis evolution, Ceroxyloideae not included), Essig (2008 and references: pericarp anatomy), Stauffer et al. (2009: labyrinthine nectaries), Angyalossy et al. (2008: secondary thickening) and Rudall et al. (2011b: apocarpy in coryphid palms), and Romanov et al. (2011 and references: fruit anatomy).

Phylogeny. [[Nypoideae + Calamoideae] (strong support for that clade) + the rest of the family (moderate support)] formed a trichotomy in a three-gene study by Asmussen et al. (2000); other characters supported these general relationships. Soltis et al. (2007a) also recovered a well-supported clade [Nypoideae + Calamoideae]. However, details of the relationships of Nypoideae and Calamoideae to the rest of the family were unclear in other studies, although Calamoideae were probably sister to all other Arecaceae, and some morphological groupings were not supported by molecular data (Hahn 2002a, b; see also Baker et al. 1999a; Asmussen & Chase 2001; Lewis & Doyle 2001). Henderson and Stevenson (2006), after a analysis of morphological and anatomical features for selected genera, discussed groupings, relationships and character evolution. They found that Phoenix and Thrinax appeared as successively sister to the rest of the family, which seemed even then rather unlikely. Asmussen et al. (2006: very good generic-level sampling, four genes) clarified this confusion and presented the rather well supported set of relationships summarized in the tree here; those parts less well supported (the monophyly of Ceroxyloideae and Arecoideae) were strongly supported by low copy nuclear DNA data (W. J. Baker, unpubl. data, in Asmussen et al. 2006). These relationships were confirmed in the comprehensive analysis of Baker et al. (2009), althouh the position of Nypoideae was not so strongly supported as that of the other subfamilies.

For morphology, phylogeny and classification in Calamoideae, see Baker et al. (1999b, 2000a, b, c). Coryphoideae include Arecoideae-Caryoteae, previously placed in Arecoideae (Uhl and Dransfield 1987; see also Dransfield et al. 2008a for a phylogeny). Ceroxyloideae include Phytelephantoideae (Dransfield et al. 2005). Phytelephas and its relatives have 4-merous flowers with up to 1000 centrifugal stamens (Palandra) and 10 carpels; Palandra also has monopodial flower clusters, unique in the family.

Baker et al. (2011, 2012) have examined phylogenetic relationships within Arecoideae; tribes are monophyletic, but relationships within the large Areceae remain unclear. Within this clade, Gunn (2004) provided a phylogeny of Cocoseae and and Eiserhardt et al. (2011a) that of the spiny Neotropical Bactridinae, which includes the climbing Desmoncus. For the phylogeny of Areceae, see Lewis and Doyle (2002) and Baker et al. (2006); Norup et al. (2006) discuss generic limits in Areceae, most members of which have a distinctive crown shaft (tribal apomorphy). Cuenca and Asmussen-Lange (2007) and Cuenca et al. (2007, 2008) discuss the phylogeny and biogeography of the largely New World understorey Chamaedoreeae; for the phylogeny of Chamaedorea itself, see Thomas et al. (2006).

Classification. Dransfield et al. (2008, see also Dransfield et al. 2005) present the outline classification followed here, but with many more details. Arecoideae here are the Arecoideae of Uhl and Dransfield (1987), but minus Caryoteae, and they also include Ceroxyloideae-Hyophorbeae (Hahn 2002b; also Baker et al. 1999a), basically, the arecoid line of Moore (1973: see Dransfield et al. 2005). Govaerts and Dransfield (2005) provide a checklist for the family, for which, see also the World Checklist of Monocots, but the best - and still improving - general resource for the family is PALMweb.

Botanical Trivia. Arecaceae have the largest leaf - Raphia sp., ca 25 x 3 m; the largest inflorescence - Corypha umbraculifera, ca 7.5 m long with some 10,000,000 flowers and 5280 m of flower-bearing axes (Tomlinson & Soderholm 1975); the largest seed - Lodoicea maldavica, to 50 cm long and 15-30 kg, which in turn produces the longest cotyledon (strictly speaking, an apocole or elongated, unifacial, non-photosynthetic part of the cotyledonary hyperphyll) which may be "several yards" or "twelve feet or more" long (Thiselton-Dyer 1910); the longest stems, perhaps up to 200 m long in Calamus manan; the oldest functioning xylem elements and sieve tubes - palms can be hundreds of years old, and there is no secondary thickening; and perhaps the longest vessels, to 3.96 m long in some calamoid palms. They also have close to the oldest viable seeds, since a seed of Phoenix dactylifera perhaps 2,000 years old has recently been germinated (Sallon et al. 2008; see also Kew Magazine, Winter 2008: 28-31).