[Re:] Gymnosperms Monophyly

[Thomas Schlemmermeyer]

 Caro Luciano,

 Maybe you should read Richard Zander's paper in Taxon 8 (1998), which
 mentions many objections to contemporate phylogenetic reconstruction in
 general. And it mentions as well problems with molecular studies in
 particular.

 I did not read the paper you mentioned, but molecular studies based on
 one gene may be seen as single-character studies. In order to
 get much information, multiple-gene studies should be done, but that is
 often incompatible with the scientist's time and money. I don't
 know how this was done in the paper in question.

 One must consider some basic and intrinsic difficulties of phylogenetic
 methods, which may, in many cases, not allow a highly plausible
 and very true reconstruction of phylogeny.

 In face of the biodiversity crisis, purely descriptive parts of taxonomy
 should be given an equally important weight.
 New descriptions can lead to the discovery of new character sets which may
 allow, in a later stage of investigation, proposals of new phylogenies.

    with friendly greetings   Thomas


On (    Fri, 23 Apr 1999 17:27:33 -0300), LUCIANO PAGANUCCI DE QUEIROZ
<lqueiroz at CASCAVEL.UEFS.BR> wrote:


>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.
>
>        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 ?
>
>        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
getti
>ng
>the attention to the caution necessary to take conclusions based only on them.
>
>        Cheers,
>
>        LUCIANO
>
>
>
>
>**********************
>LUCIANO PAGANUCCI DE QUEIROZ
>Universidade Estadual de Feira de Santana
>Departamento de Cijncias Biolsgicas
>Herbario
>Km 03 - BR 116, Campus
>44031-460, Feira de Santana, Bahia, Brasil
>Fone (075) 2248021
>Fax (075) 2248019
>E-mail: lqueiroz at uefs.br
>


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Thomas Schlemmermeyer
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Residjncia:
Thomas Schlemmermeyer
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