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Date: Wed, 02 May 2001 17:34:01 -0700
From: Richard Olmstead <olmstead@u.washington.edu>
To: phylocode@ouvaxa.cats.ohiou.edu
Subject: Re: subscribers
The PhyloCode makes no provision for naming paraphyletic groups. If Lophotrochozoa turns out to be synonymous with Bilateralia, then it simply is dropped as a formal name - Bilateralia remains perfectly good for the group. If anyone wants to use informal names for paraphyletic groups, such as 'fish,' 'reptiles,' 'green algae,' 'bryophytes,' or 'lophotrochozoa,' that's up to them. After all, nomenclature, like language, is for communication and in language, precision makes for clarity. It seems to me that the goal of those who promote PhyloCode is to convince systematists who believe that taxonomy should be a system of naming monophyletic groups to follow a series of naming principles laid out in the PhyloCode. Systematists who want to continue to give formal recognition to paraphyletic groups are a shrinking minority in our field and even many of the most vocal opponents of PhyloCode oppose such taxonomy. There is nothing in the neo-Linnaean hierarchy of ranks that is incompatible with a strictly monophyletic classification. Many who oppose the PhyloCode think we can do just fine within that framework. I happen to disagree. The argument against ranks and binomial nomenclature is separate from the argument against recognizing paraphyletic groups. Both are important elements of PhyloCode, but I think this recent string of comments hasn't kept them separate. Dick Olmstead >Chris, > In the case at hand, if cladistically-defined and "precise" >Lophotrochozoa turns out to be a synonym of Bilateralia, the cost of that >precision is going to be pretty steep. > The contents and characteristics will expand considerably (with the >addition of all deuterostomes and ecdysozoans). Numerous trees and cladograms >in the intervening literature will be incorrect, and the accompanying text >confusing as well for those unaware of the whole story. Lots of confusion and >inaccuracy in the name of precision (no thank you). > And what a waste of a name. Couldn't call the paraphyletic group >lophotrochozoans any more. Would be stuck with an explanation like: > Lophotrochosozoa was formerly erroneously restricted to the >"non-ecdysozoan, non-deuterostome bilateralians", but then later more complete >cladistic analyses showed this clade to be a heterodefinitional synonym of >Bilateralia. > But in the meantime, what I fear most is that some workers, assuming >that Ecdysozoa and Lophotrochozoa are really sister groups, might begin using >ecdysozoans as outgroups in cladistic analyses of groups in the supposed clade >Lophotrochozoa (as we see it in the literature from 1995-2001). This would >produce an even bigger mess. > My main warning on this issue is that neither ecdysozoans (nor >deuterostomes) should be used as outgroups to the presently constituted >Lophotrochosozoa. I can see how workers would be tempted to do this, since >outgroup selection was one of the criticisms levelled by Conway Morris et al. >That is one criticism I definitely wish they had not made, because it could >have workers cladistically jumping out of the frying pan and into the fire >(making the outgrouping problem worse rather than better). Better to use a >cnidarian outgroup than to use an ecdysozoan (which I believe is really an >ingroup). > That's my advice, Ken Richard Olmstead Associate Professor of Botany and Herbarium Curator Editor, Systematic Biology Department of Botany For express mail services: Box 355325 Department of Botany University of Washington Hitchcock Hall Rm 423 Seattle, WA 98195-5325 University of Washington USA Seattle, WA 98195 Office: 206-543-8850 lab: 206-543-6594 herbarium: 206-543-1682 FAX: 206-685-1728 email: olmstead@u.washington.edu http://depts.washington.edu/botweb/facbio/olmstead.html