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Date: Tue, 01 May 2001 17:08:55 -0500
From: "David M. Hillis" <dhillis@mail.utexas.edu>
To: phylocode@ouvaxa.cats.ohiou.edu
Subject: Lophotrochozoa
> > Lophotrochozoa is a perfect example of a group which should NOT be >formally recognized. It is almost certainly a broadly paraphyletic group that >gave rise to the holophyletic Ecdysozoa grouping of phyla. They are simply >non-ecdysozoan bilateria, and the notion that they are the sister group to >ecdysozoans is going to be very difficult to dispel. > These and other formal intermediate rank names (Coelomata, Protostomia, >Uniramia, etc.) do more harm than good in determining how the various >invertebrates are related to one another. In my opinion, PhyloCode will only >accelerate the generation of such problems. > -----Ken Kinman 1. Lophotrochozoa cannot be a paraphyletic group, because it was DEFINED as a monophyletic group (the last common ancestor of bryozoans, phoronids, brachiopods, annelids, and mollusks, and all the descendants of that common ancestor). This definition was written well before any draft of the PhyloCode. 2. The discovery and definition of Lophotrochozoa preceded the definition of Ecdysozoa, and even the paper that described Ecdysozoa supported its sister-group relationship to Lophotrochozoa. 3. I'm aware of no published evidence that supports your claim that Lophotrochozoa is not the sister-group of Ecdysozoa; perhaps that is why this will be a difficult notion to dispel. I'd be happy to reconsider my recognition of this clade (that is, synonymizing it with Bilateralia) if I'm presented with compelling evidence that these two taxa are synonyms. That is what science is all about. 4. Even if your premise is correct, and Lophotrochozoa is a synonym of Bilateralia, then it will be an easy matter to synonymize the former with the latter. If Lophotrochozoa had been named as a ranked taxon, then all the other nearby ranks among metazoans would have had to be changed, and then changed back again if Lophotrochozoa is really found to be synonymous with Bilaterialia, as you suggest without supporting evidence. What a waste of everyone's time. This is actually a great example of why ranking, if it is done at all, should be completely separated from the task of discovering and naming higher taxa. 5. Naming Lophotrochozoa as an unranked clade allows us to focus on the science, rather than arbitrary decisions of rank. We can legitimately argue about whether Lophotropchozoa is the sister-group of Ecdysozoa or a synonym of Bilateralia, without arguing about what ranks may be assigned to these taxa. I find this much more economical than arguing about whether bryozoans, phoronids, brachiopods, annelids, and mollusks form a monophyletic sister group to Ecdysozoa on one hand, versus the position that the clade that includes bryozoans, phoronids, brachiopods, annelids, and mollusks also includes Ecdysozoa on the other hand. For me, nomenclature is a tool for talking about the Tree of Life, and I don't want a system that restricts me to talking about a few arbitrary clades. The PhyloCode doesn't restrict you from ranking taxa if you want to, but it does free the rest of us to focus on the whole phylogeny of life. 6. Many of us care a great deal about the details of the Tree of Life, and I find your argument that we should be unconcerned about "intermediate rank" taxa insulting. You are basically saying that our interests are unimportant. I don't restrict you from ranking taxa if you want to do so; please don't restrict the rest of us from naming the things that we think are important (the parts of the Tree of Life), and please don't try to force us to use ranks that we find distracting, misleading, unnecessary, and cumbersome. I notice that you have no problem talking about the higher phylogeny of invertebrates without mentioning ranks...what would ranks add to this discussion? David Hillis David M. Hillis Director, School of Biological Sciences Director's office: 512-232-3690 (FAX: 512-232-3699) Alfred W. Roark Centennial Professor Section of Integrative Biology University of Texas Austin, TX 78712 Research Office: 512-471-5792 Lab: 512-471-5661 FAX: 512-471-3878 E-mail: dhillis@mail.utexas.edu