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CORE EUDICOTS: flowers rather stereotyped: 5-merous, parts whorled, calyx and corolla distinct, stamens = 2x K/C, developing internal to the corolla, (often numerous, but then often fasciculate and/or centrifugal in development), pollen tricolporate, [G 5], [3] also common, compitum +, placentation axile, stigma not decurrent; endosperm nuclear; fruit dry, dehiscent, loculicidal [when a capsule]. [Back to Index]

The age of the core eudicot clade has been suggested to be some 113 million years (Leebens-Mack et al. 2005, but see sampling), while Anderson et al. (2005) suggest a similar figure - stem group to 116 million years old, diversification by ca 109 million years before present. The oldest known eudicot fossil flower is from the Cretaceous-Cenomanian, 96-94 million years ago (Basinger & Dilcher 1984). For general information on core eudicot diversification, see Magallón et al. (1999); most of the estimates of percentage diversity of clades are taken from this work. The diversification rates of many of the clades are higher than those in other angiosperms (Magallón & Sanderson 2001).

It is difficult to see floral development of Berberidopsis corallina as being a real "link" in the evolution of the flower of core eudicots (cf. Ronse De Craene (2004, 2007), not least because it would entail such evolutionary scenarios as the separate origin of such a flower in Aextoxicon AND and also the paraphyly of the order or even family. However, flowers of many core eudicots are very distinctive, as is indicated by the characterisation above. Sepals usually have three traces and petals have one, although there is considerable discussion as to the distinction between and evolution of sepals and petals (see Ronse de Craene 2008 and references). Taxa that have flowers with many stamens are scattered throughout the core eudicots. A number of these taxa initially have only five or ten primordia, in the former case, the primordia usually arise opposite the petals, rather than alternating with them. Numerous individual stamens then develop from these few initial primordia, and development is often centrifugal (cf. esp. magnoliids and the ANITA grade). At maturity, the stamens themselves may be more or less connate or in fascicles (see esp. Corner 1946b; Weberling 1989; Leins 2000 and references; Prenner et al. 2008). However, there may be considerable variation in staminal development between closely related multistaminate taxa (e.g. Hufford 1990; Ge et al. 2007). Chase (2005) noted that in Santalales some floral parts, particularly stamens, might have several whorls, and this perhaps suggested that canalisation of floral development was less than in some other core eudicots; whether Santalales really are different in this respect from other core eudicot groups remains to be established. Flowers with many stamens are much less common in the asterid I + II clade (q.v. for discussion) and there polyandry appears to be of a rather different nature.

The occurence of ellagic acid has a distribution similar to that of polyandry in the eudicots. Seed coats with a mechanical layer more than a single cell thick occur throughout BLAs, but again, seed coats of the asterid I + II clade are rather different, usually being only one or two cells across.

This clade is strongly supported, e.g. Chase et al. (1993), D. Soltis et al. (12003a), and Nandi et al. (1998), although Gunnerales (q.v.) have in the past also been included in core eudicots; Gunnerales and core eudicots are here considered sister taxa simply to make the eudicot clade readily characterisable (the floral morphology of Gunnerales is unlike that of core eudicots, but more like that of Proteales, etc.). Relationships within core eudicots are unclear. As things stand, there is a major basal polychotomy there, and there is in fact little support for the positions of some of the orders assigned below to clades of this polychotomy, such as Dilleniales with Caryophyllales, Vitales and in particular Saxifragales with rosids. Thus in some studies Dilleniaceae are sister to Caryophyllales, but with only very moderate support; D. Soltis et al. (2003a) provides rather stronger (83% jacknife) support for this position (see also Soltis et al. 2007a). It is also possible that Caryophyllales + Dilleniales and Santalales form a clade (D. Soltis et al. 2000); Carlquist (2006) suggested that non-bordered perforation plates was a possible similarity between Santalales and Caryophyllales. Caryophyllales were linked with with asterids in a large 18S ribosomal DNA analysis (Soltis et al. 1997), albeit with only weak support (see also Hilu et al. 2003). In recent studies using whole chloroplast genomes (Jansen et al. 2006a, esp. 2006b; Hansen et al. 2007; Cai et al. 2007; Ruhlman et al. 2006; Jansen et al. 2007; Moore et al. 2007; Logacheva et al. 2008) support for this position is stronger, however, Berberidospidales, Dilleniales, Santalales and Saxifragales were not included. [Caryophyllales + Santalales] were sister to asterids in some analyses (e.g. Nickrent et al. 2005); in other analyses including a reduced sampling and two chloroplast genes Santalales and Dilleniales were also in the area, but also with little sup