[Taxacom] Defining polyphyly

Richard Zander Richard.Zander at mobot.org
Wed Dec 15 12:47:02 CST 2010

At the risk of hammering away at this, a paraphyletic group and its apophyletic (or autophyletic) evolutionary dongle are specified by synapomorphies on a cladogram. Taxa, on the other hand, are specified by diagnoses or descriptions, where the autapomorphies are important in evolution. Phylogeneticists do "tree-thinking" which to them means sister-group thinking and evolution of traits.

Thus, phylogeneticists specify only similarities, but evolutionary systematists use both similarities and differences. Both sister-groups and ancestor-descendant relationships are important, but even more important is the fact that taxa are what evolve, not relationships in a pattern.

* * * * * * * * * * * * 
Richard H. Zander 
Missouri Botanical Garden, PO Box 299, St. Louis, MO 63166-0299 USA 
Web sites: http://www.mobot.org/plantscience/resbot/ and http://www.mobot.org/plantscience/bfna/bfnamenu.htm
Modern Evolutionary Systematics Web site: http://www.mobot.org/plantscience/resbot/21EvSy.htm

-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Curtis Clark
Sent: Wednesday, December 15, 2010 8:38 AM
To: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Defining polyphyly

On 12/15/2010 5:09 AM, John Grehan wrote:
> There's the hinge of it all - whether paraphyletic groups are any more 'natural' than those that are polyphyletic.
A paraphyletic group can be specified by synapomorphies (a set for the 
stem group and other sets for the exgroups), so it is as "natural" as a 
monophyletic group. The question is rather, is it useful. And that's 
where the disagreement seems to center.

Curtis Clark                  http://www.csupomona.edu/~jcclark/
Director, I&IT Web Development                   +1 909 979 6371
University Web Coordinator, Cal Poly Pomona


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