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Floral anatomy question
Did you read the warning to the website and its various family trees it
presents? http://www.mobot.org/MOBOT/Research/APweb/ !!IMPORTANT - WARNING TO ALL USERS!! v All clades are hypotheses of relationships, and as hypotheses they may be overturned. Even though I have for the most part been conservative, changes in our ideas of relationships, and hence in the clades we talk about, are particularly likely in parts of Caryophyllales and Malpighiales. Taxa whose relationships are still largely unknown or only partly known - apparently not many, although we must expect to find a few more seriously misplaced genera - should also not be forgotten. Thus some changes are to be expected, but changes are neither a defect of cladistics, nor a necessary consequence of the use of molecular data. ************************ Cladistics is statistical and only as good as the number of different character states used and the significance given to them. If certain ones are included or excluded the resulting trees can differ substantially (and they do). This is the more realistic tree but it still leaves several orders hanging. http://www.mobot.org/MOBOT/Research/...eltreemap.html You have to realize that most of the trees are preliminary and tentative and not all of the families (genera) are thoroughly studied and the trees are already out-of-date. Most of what is posted on the Internet is second hand info taken from old papers. Of course all if this remains meaningless and mystical if you have no idea what the plants in the various orders actually look like. 1. The primitive trimerous dicots. (maybe call them "Predicots" or "Protodicots"?) Amborellales Nymphaeales Austrobaileyales Chloranthales Magnoliales Laurales Cannellales Piperales Ceratophyllales 2. Monocots. Acorales Alismatales Asparagales (Many of the families listed are amorphous with many of the genera misplaced or considered to be of uncertain affinity. Several of the families have been defined differently is recent papers.) Dioscoreales Liliales Pandanales Arecales Poales Commelinales (Haemodoraceae is polymorphic) Zingiberales 3. True (4-5 merous) Dicots. (so called "Eudicots") Ranunculales to Dipsalales Stewart Robert Hinsley wrote in message ... 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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