Re: New alligatoroid paper as example for amateur cladists

["Jonathan R. Wagner" <znc14@TTACS.TTU.EDU>]

At 07:40 AM 7/6/99 -0400, Philidor11@aol.com wrote:
><< The author concludes that he has found certain taxa to be monophyletic, 
>yet these taxa were defined as monophyletic taxa. I may have missed a 
>sentence or two explaining this. >>
>
>I think you did.  The word 'yet' implies a contrast, but I don't see one.  If 
>you substitute the word 'and' then you have an a=a observation.  I follow 
>your subsequent definition of monophyletic taxa among dinosaurs, but I can't 
>connect it back to this observation.  My best guess at the moment is that you 
>mean different classification approaches lead to the same result, but I would 
>like to be sure.

        Ok, I'm not sure I follow you either, but here goes:
        There are several ways to establish taxa. Two prominant methods, the
modernised Linnean ("evolutionary taxonomy") method, which I will simply
call Linnean, and the phylogenetic method. The Linnean method involves
erecting taxa which are defined on characters, usually shared derived
characters these days. The content of these taxa may then be tested for
monophyly (although paraphyly is often acceptable in such taxonomic
schemes). In the past, it was therefore customary to consider monophyly a
testable attribute of a taxon.
        In phylogenetic taxonomy, taxa are DEFINED to be monophyletic (e.g.
"the most recent common ancestor of _Ephemerella_ and _Pongo_ and all of its
descendants"), and therefore testing their monophyly is pointless. These
taxa are monophyletic from the get-go, and the range of testable attributes
does not include monophyly (but still includes other things like content,
diagnostic characters, FAD, LAD, etc.).
        So, what do we make of an author who uses phylogenetic taxonomy (in
which his taxa *must* be monophyletic), but insists that he has tested his
taxa for monophyly? Herein lies the contrast I emphasized when I confused
you; why is this fellow trying to prove something which he has accepted a
priori?
        Well, this appears to be an artifact of the transition from Linnean
to phylogenetic taxonomy. While the author has accepted phylogenetic taxon
definitions, he is testing the monophyly of the old, non-phylogenetic taxon,
or more properly they are testing to see if the species included in the old,
non-phylogenetic taxon form a monophyletic group exclusive of other species
in the analysis. Unless Dr. Brochu would like to correct me here...
        I hope this clears up any confusion. If not, fire away with the
questions.

        Wagner

        "Would this hatchet-weilding monkey by any chance have a red butt?"
                                -- I. M. Weasel
--------------------------------------------------------------------------------
     Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
 "Only those whose life is short can truly believe that love is forever"-Lorien