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Date: Thu, 09 Sep 2004 16:05:58 -0400
From: [unknown]
To: phylocode@ouvaxa.cats.ohiou.edu
Subject: Re: Panstems
>My responses to JRW=3D92s comments on restricting the types of defin= itions =3D allowed and on panstems.< In tandem with Mike Keesey's comments, I would like one or more answe= rs to =3D a lingering question from the (very successful) Paris meeting: In response to Dr. Padian''s suggestion that definitional types be = =3D restricted to node- and stem-based classes, Dr. de Queiroz responded = (at =3D least twice) that he felt it was inappropriate to impose restrictions= on =3D HOW phylogenetic taxa should be defined. Although I believe Dr. Padia= n's =3D points were valid, and I would be willing to consider his proposal, I= also =3D very much respect Dr. de Queiroz's position. >There are several reasons why allowing only one type of phylogenetic= =3D definition is inappropriate. First, it goes against the fundamental = =3D principle of taxonomic freedom. Taxonomists should be free to name = =3D whatever t clades they want to name. Second, allowing this type of = =3D freedom is important because it=3D92s the only way to achieve a close= =3D correspondence between the connotations of a name and the properties = of =3D the clade to which it refers. For example, if a person wants to name= the =3D clade of flying dinosaurs (Volodinosauria?) but is forced to use a = =3D node-based definition, then the name is likely to end up not referrin= g =3D even to the closest relevant node. For example, we might define such= a =3D name as referring to the clade stemming from the =3D93Archaeopteryx n= ode=3D94 =3D based on the idea that Archaeopteryx is the most distantly related ta= xon =3D to modern birds that is (currently) thought to have been able to fly.= =3D However, if we later infer either 1) that Archaeopteryx was not able = to =3D fly, or 2) that more distantly related taxa were also able to fly, th= en =3D name becomes disassociated from the clade to which it was originally = =3D intended to apply. Third, even if we were to agree that only one typ= e of =3D phylogenetic definition is permissible, we probably couldn=3D92t agre= e on =3D which one, given that different people favor different types (and som= e of =3D us favor all of them). I guess JRW actually favors two. I thought t= hat =3D KP advocated only node-based definitions in his general talk (perhaps= =3D I=3D92m confusing his view with that of BDM), but I noticed that in h= is =3D abstract he used both stem- and apomorphy-based.< >I also want to comment on the idea that we need to make things simpl= e for =3D our colleagues so that they don=3D92t screw things up, which was impl= ied by =3D several people who argued for allowing only one type of definition. = This =3D is the type of reasoning that is characteristic of the =3D93hardening= =3D94 of =3D a movement, to use Gould=3D92s term. Although simple rules (symptoms= of =3D hardening) are often advantageous in the short term for getting peopl= e to =3D jump on the bandwagon and to separate a new movement from its predece= ssors,=3D they usually turn out to be misguided and to impose unnecessary rest= rictio=3D ns in the long run. That was true of the hardened neo-Darwinist posi= tion =3D that selection acts only at the level of individual organisms. It wa= s =3D true of the hardened numerical taxonomist position that taxonomy shou= ld be =3D based only on observed similarity regardless of its underlying cause.= And =3D it was true of the hardened cladist position that phylogenetic relati= onship=3D s should only be inferred using parsimony methods. Those views all s= eem =3D pretty foolish in retrospect, and they have all exerted retarding eff= ects =3D on the development of their respective fields. I think it would be a= huge =3D mistake to shackle phylogenetic nomenclature with an analogous over-s= implif=3D ication.< However, as evidenced by the vote late in the meeting, several meetin= g =3D participants, including Dr. de Queiroz, are in favor of restricting W= HICH =3D NAMES can be defined (specifically, by supporting the non-binding = =3D resolution that symposium volume authors be REQUIRED to follow the = =3D "panstem" convention). I understand the arguments for panstem nomencl= ature,=3D and I am sympathetic. What I do not understand is the justification= for =3D upholding scholarly freedom on one issue, then denying it on another.= Was =3D this simply an indication that these individuals would PREFER that pa= nstem =3D nomenclature be employed, inflated to the status of a "requirement" = only =3D because the vote was non-binding? Or do these individuals actually su= pport =3D moving from a Phylogenetic Nomenclature with very limited rules on w= hich =3D names should be employed to a Phylogenetic Taxonomy, with a rigid sys= tem =3D for choosing and employing appropriate names? >There is an important difference between taxonomic and nomenclatural= =3D freedom. The PhyloCode follows the traditional codes in adopting = =3D taxonomic freedom as a fundamental principle. Thus, neither the tank= -based=3D codes nor the PhyloCode prohibits authors from naming any type of gr= oup =3D (note that although the PhyloCode is designed for naming clades, it d= oes =3D not prohibit the naming of paraphyletic or and polyphyletic groups), = nor =3D do the codes place any restrictions on the composition of the groups = other =3D those that are necessary for specifying the references of the names (= i.e., =3D the necessary inclusion of the type in rank-based nomenclature, the = =3D necessary inclusion of internal specifiers and exclusion of external = =3D specifiers in phylogenetic nomenclature). In contrast, all codes pla= ce a =3D number of restrictions on what names are permitted=3D97that is, on no= menclatu=3D ral freedom. In other words, there is no principle of nomenclatural = =3D freedom in any of the codes. Nomenclatural codes are, after all, set= s of =3D rules about what is permitted, and what is not permitted, with respec= t to =3D names. Thus both the rank-based codes and the PhyloCode permit only = the =3D use of a particular alphabet, and they both prohibit various diacriti= cal =3D marks. Moreover, the rank-based codes require the names associated w= ith =3D particular ranks to have particular terminations and for some of them= to =3D be based on the names of included taxa. Similarly, the PhyloCode con= tains =3D a recommendation (10A), which Phil and I are going to propose be modi= fied =3D and made into a rule, that places significant restrictions on the = =3D definitions (conversion) of existing names (e.g., you aren=3D92t allo= wed to =3D convert the name Mammalia for a clade of beetles). If the PhyloCode = were =3D to require the names of total clades to be based on the names of thei= r =3D corresponding crowns with the addition of a standard prefix, this wou= ld be =3D analogous to certain nomenclatural requirements of the rank-based cod= es. =3D Here I should emphasize that one should not confuse the elimination o= f the =3D associations of names with ranks, which is fundamental to phylogeneti= c =3D nomenclature, with the elimination of standard affixes, which is perf= ectly =3D compatible with phylogenetic nomenclature as long as the affixes do n= ot =3D signify rank. In any case, the point is that a rule requiring adopti= on of =3D the Pan- convention would not violate the fundamental principle of = =3D taxonomic freedom, and thus it is not inconsistent with advocating th= e =3D freedom to use multiple types of definitions.< =3D20 Kevin 9 Sep 2004 Kevin de Queiroz Division of Amphibians & Reptiles Smithsonian Institution P.O. Box 37012 NHB, Room W203, MRC 162 Washington, D.C. 20013-7012 Voice: 202.633.0727 FAX: 202.357.3043 E-mail: dequeirk@si.edu