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Date: Tue, 06 Feb 2001 09:18:26 -0500
From: david baum <dbaum@oeb.harvard.edu>
To: PhyloCode@ouvaxa.cats.ohiou.edu
Subject: Re: apomorphy-based names
I just wanted to endorse David Hillis' criticism of apomorphy-based names: namely that it is pretty much impossible to provide an unambiguous definition of any apomorphy that would adjudicate cases in which future taxa are found to have intermediate conditions. Additionally, if there were no apomorphy-based names the phylocode would have added value because one could query the Phylogenetic Nomenclature database with a tree and get back the correct name for each named clade. I believe that this bioinformatic advantage could be the key to convincing the broader biological community that the PhyloCode is the way to go. at the same time, I remain unconvinced that, as Kevin put it, ".... sometimes an apomorphy-based definition is the appropriate definition for the clade concept being named." A good synapomorphy certainly can provide good evidence that one has identified a clade, and can be immensely useful when communicating the identity of a clade to somebody. However, I cannot see why it would ever be the appropriate DEFINITION of a clade concept. What is to stop you aiming for a stem-based or node based definition, even a conservative one listing lots of specifiers? Consequently I disagree with Jonathan Wagner's recommendation that "clade names derived from apomorphy names be given apomorphy-based definitions." If the apomorphy is a strong one then the clade is strong in which case one can always find some conservative stem-based or node-based definition that will accurately point to the clade of interest. And if, down-the-road, the name no longer applies to the clade for which the character is apomorphic - so be it. Systematists are very good at not reading too much into the literal meaning of names. David may be right that for internal political reasons we cannot yet ban apomorphy-based definitions. But I hope that one day the vertebrate paeontological types, and whoever else is inclined towards apomorphy-based definitions, can be convinced to make-do with stem-based and node-based definitions. David P.S. I think "node-based," "stem-based," and "apomorphy-based" should be in the PhyloCode glossary David Baum Dept. Organismic and Evolutionary Biology Harvard University Herbaria 22 Divinity Avenue Cambridge MA 02138 Tel: (617)496-6744, -8766 Fax: (617)495-9484 dbaum@oeb.harvard.edu http://www.herbaria.harvard.edu/~dbaum