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Date: Tue, 10 Feb 2004 09:15:11 +0300
From: "Igor Ya. Pavlinov" <igor_pavlinov@zmmu.msu.ru>
To: PhyloCode <phylocode@ouvaxa.cats.ohiou.edu>
Subject: Re: RE: a comment on ancestor
----- Original Message ----- From: Kevin de Queiroz <Dequeiroz.Kevin@NMNH.SI.EDU> To: <phylocode@ouvaxa.cats.ohiou.edu>; <igor_pavlinov@zmmu.msu.ru> Sent: Tuesday, February 10, 2004 12:48 AM Subject: Re: RE: a comment on ancestor > Igor Ya. Pavlinov wrote: > > >And in some of the articles special > >consideration should be paid to not rare (rather, near to unversal) > >situations when a group is treated as holophyletic in one hypothesis and > as > >paraphyletic in another (Pinnipedia is good an example). All this is > needed > >to make more clear what used to happen with the name in situation when > the > >name-bearing taxon losts its holophyletic status. > > How a taxon name such as "Pinnipedia" is to be treated in the context of > different phylogeentic hypotheses should be clear from the way in which the > name is defined. Thus, if Pinnipedia is defined simply as the least > inclusive clade contaning seals, sea lions, and walruses, this name will > always refer to a monophyletic (holophyletic) taxon, though it will include > only these three subgroups in the context of some phylogenetic hypotheses, > while it will include one or more fissipeds (animals without "flippers") in > the context of other hypotheses. The name would never refer to a > paraphyletic or polyphyletic taxon. In contrast, if a qualifying clause > similar to the one I described earlier (e.g., "provided that their aquatic > adaptations did not evolve convergently") were to be included, then the name > Pinnipedia would be used for the clade of seals, sea lions, and walruses in > the context of those phylogenetic hypotheses in which they formed a clade; > in the context of hypotheses in which these three taxa did not form a clade, > the name would not be used. In order for the name to refer to a > monophyletic taxon in the context of some phylogenetic hypotheses and a > paraphyletic or polyphyletic taxon in the context of others, the name would > have to be defined along the following lines: Pinnipedia = the taxon > composed of seals, sea lions, and walruses (and no other taxa) regardless of > their phylogenetic relationships. > > >What seems to be also important, is treatements of procedures by which > >phylogenetic hypotheses are elaborated. For me, it is clear that trees > >obtained by middle-point rooting or UPGMA procedures are methodologically > >phenograms rather than cladograms. So, as a clade is thought to be > validly > >recognized within a particular phylogenetic hypothesis only, then what > are > >criteria of validity of the hypothesis itself? Surely consideration of > such > >a topic within the Phylocode will cause many objections, but at least > some > >indication that not all trees are phylogenetic ones, although are called > so, > >would be no less desirable than undication of criteria of publication > >validity. > > The method or methods used to infer phylogenetic relationships is a > taxonomic rather than a nomenclatural issue; therefore, it is outside of the > jurisdiction of the PhyloCode. Consequently, systematists are free to use > whatever methods they like (even UPGMA!) to infer phylogenetic > relationships; however, some methods (such as UPGMA) will make it more > difficult for them to satisfy other requirements of phylogenetic nomenclatue > (such as providing a diagnosis), and their use may affect how widely the > conclusions are accepted by other researchers. > THAT'S JUST WHAT SAID AT THE VARY BEGINNING OF CURRENT DISCUSSIAN: APPLYING PHYLOCODE WITH ITS STRICT DIFINITION OF OBJECTS TO BE NAMED VALIDLY SEEMS TO LEAD TO GREAT INSTABILITY OF NOMENCLATURE. > Kevin > > > Kevin de Queiroz > Division of Amphibians & Reptiles > Smithsonian Institution > P.O. Box 37012 > NHB, Room W203, MRC 162 > Washington, D.C. 20013-7012 > Voice: 202-357-2212 > FAX: 202-786-2979 > E-mail: dequeiroz.kevin@nmnh.si.edu