Real taxa

[Ricardo at Mizzou1.Missouri.edu García]

Dear all

Several authors thinks that species and all other taxa should be treated
(e.g. recognized) in the same way, this means that the dichotomy is between
natural and no-natural groups (e.g. monophyletic and no-monophyletic
groups), some of this ideas are in the chapters of Mishler & Theriot (and
references there) of the Wheeler & Mier book (Species concepts and
phylogenetic theory, 2000). The ideas there are developed around species,
but the debate about why should use the same methods in all taxonomical
ranks  are there. Another very good review of the species criteria are in
Wilson (ed) 1999. Species MIT Press

How to select the "appropriated" taxonomical rank (genera, tribe etc) for a
group is a matter of debate, mainly because this issue is out of the scope
of the formal methods of systematics (cladistics). This issue are related to
the dichotomy grouping vs. ranking, grouping is a matter of natural
relationships (phylogeny) and are well founded in cladistics, ranking is at
this moment out of any formal and/or wide accepted method. Some ideas about
this dichotomy are in Cristoffersen 1995 (Syst. Biol.44: 440-454). What
criteria we must use for ranking?, some ideas are around minimize the impact
over established taxonomy in the group (for nomenclatural and practical
reasons), maybe using some previous recommendations (e.g. Nelson 1974, Syst.
Zool. 22: 344-359), extreme positions goes over drop the Linnaean ranking
for a new ranking method, but this is a more difficult issue, arguments pro
starts in de Queiroz & Gauthier 1992 (Annu.Rev.Ecol.Syst. 23:449-480), and
several critical reviews are in the vol. 69 (2003) of Botanical Review. Some
philosophical issues about natural groups vs. Linnaean ranks are in
Ereshefsky 2001 The Poverty of the Linnaean Hierarchy.

 From a mycological perspective about how to recognize and rank above-species
taxa exist some suggestions, practical and theoretical (some of those are
out of the cladistic perspective) in Mycologia Helvetica vol. 6 (1994).

In short, for the problem of how to rank a above-species taxa 1) the taxa
should be natural, monophyletic (I guess all are agree with this) 2) try to
minimize the impact over previous classifications (this are matter of
debate) 3) try to support your taxa in extra characters, for molecular
phylogenies try to get support from morphology, ecology, distribution etc 4)
support your decision in previous ranking proposals for your group, maybe
this can help

Of course this issue are currently matter of debate, and contributions are
very welcome, I hope this helps with your practical problem

Very best



C.Dr. Ricardo García-Sandoval
Micología, Herbario FCME,
Facultad de Ciencias, UNAM.
Apto. Postal 70-399, Cd. Universitaria
C.P. 04510, Coyoacan, D.F. MEXICO

Tel. 52(55)56224908
Fax  52(55)56224828

Comité Mexicano de Sistemática y Biogeografía

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