Gymnosperms Monophyly

Fri Apr 23 17:27:33 CDT 1999

Dear Taxacomers,

        I just read a paper by Duff & Nickrent (Am. J. Bot. 86:372-386, 1999)
about Land Plants Phylogeny based on mitochondrial rRNA. The conclusions
obtained by the authors took me to question the risks of just interpreting
phylogenies based only in molecular data. One of the groups found as
monophyletic was the Gymnosperms, that appears as sister group of the
Angiosperms. =20
        I think that this conclusion is strongly biased by the gaps in the
molecular data for fossil plants, obviously unavoidable. The lack of these
data does not force the "Gymnosperms" to appear as a monophyletic group in
an cladistic analysis - thus, the formation of a clade for the extant
groups of Gymnosperms is of relevance. Even so, this does not mean that
Gymnosperms could be concluded to be, in fact, a monophyletic group. The
acceptance of this idea, placing these plants as a sister group of the
flowering plants, implies in that Angiosperms would share an ancestral with
"Gymnosperms". In this case, in what group would be placed the first seed
plants ? =20

        I think, therefore, that the main goal of these studies, where important
gaps of this kind are inevitable for key taxa, is to indicate the possible
relationships existing between extant groups. However, in the absence of
morphological information, it seems to me be impossible to assume
conclusions about monophyly of the involved groups.

        I am not advocating against molecular data in systematics but just getting
the attention to the caution necessary to take conclusions based only on=



Universidade Estadual de Feira de Santana
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