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Floral anatomy question
In article m,
Cereoid+10 writes Presently there are three primary clades of flowering plants recognized. 1. The primitive trimerous dicots. 2. Monocots. 3. True (4-5 merous) Dicots. (so called "Core Eudicots") It is the first clade that is in need of a simple easy to understand name. * It is also far from obvious that the first group is a clade, many sources reckoning it as a paraphyletic group. Judd et al (1 edn, start of chapter 8) give 6 alternative cladograms, in none of which are the "primitive" dicots a clade. Tree of Life http://tolweb.org/tree?group=Angiosp...=Spermatopsida has yet another cladogram which has three basal lineages (Amborallales, Nymphales and Austrobaileyales), and a pentachotomy in the Euangiosperms. (It does have most of the primitive euangiosperms in a tetrachotomous magnoliid clade.) Angiosperm Phylogeny Website has a similar cladogram http://www.mobot.org/MOBOT/Research/...apweb2map.html I notice, that if you ignore the ANITA taxa, this has restored the monocot-dicot dichotomy, with Ceratophyllales incertae sedis. * Your trichotomy excludes some plants, viz. the basal eudicots. The eudicots are the clade with primitively tricolpate pollen, not all of which have 4-5-merous flowers. The Core Eudicots are a group therein, excluding, at least, Gunnerales, Ranunculales and Proteales. Whether the Core Eudicot clade is equivalent the clade which has primitively 4-5-merous flowers is the point under discussion; there's enough variation in the floral morphology of non-rosid, non-asterid eudicots that it is not obvious to me what the character polarities should be on a cladogram. So what if the AGP uses the name "Core Eudicots" for the true dicots. It is silly and redundant. As used in common botanical parlance, the term "dicot" has a much deeper meaning than just the number of seedling cotyledons. Yes, it refers to a suite of traits which distinguishes the combination of the basal angiosperms and tricolpates from the monocots, one of which is the number of seedling cotyledons. (Not all of which are universal in either group, due to subsequent changes of character states.) Dicots are angiosperms minus monocots only in your antiquated understanding. The present concept is that dicots are (4-5 merous) angiosperms minus monocots minus trimerous dicots. Not on Tree of Life, not on Angiosperm Phylogeny Website, not in Judd et al, nor in any other source I've seen. Have you a citation for this "modernised" redefinition of the term dicot? -- Stewart Robert Hinsley |
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