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Re: Paraphyly and sister taxa (was Re: AMARGASAURUS SATTLERI)



Wagner wrote...
>Note, of course, that, with respect to their
>component germ cell lineages, an organism is paraphyletic).

    Hell yes.  A truly honest phylogeny would code all the individual cells
(or rather genomes) in an organism as OTUs.  You would have a huge mass of
billions or trillions of branches representing all the cell divisions in a
body over the course of its lifetime, with a few isolated little branches
coming out of the "germ cell clade", and uniting with isolated branches from
the germ cell clade of your spouse to produce huge radiations representing
the cells of your children.  The whole history of the Metazoa would look
like trillions and trillions of impossibly huge adaptive radiations going
completely extinct except for a few individuals from a single "clade", which
give rise to the next huge radiation.  Screw eliminating genera and species;
try getting THAT system popularized.

>Some recent systematists have begun insisting upon monophyletic
>genera.

     Wait a sec...determining the membership of species into a genus is a
completely arbitrary matter of convenience, so the claim can't even be made
that making genera monophyletic stops making them "artificial" or
"unnatural" groupings.  What is the point on insisting on monophyletic
genera?  Selecting any practical OTU, even an individual organism, is an
arbitrary choice.  Unless we really do want to start coding individual cell
genomes as OTUs, they always will be.
    Even choosing monophyletic clades based on common descent as a basis for
taxonomy is an arbitrary convention.  If you take a bunch of individual
organisms that lived and died at different times and different places, and
view them as a single entity ("family", "clade", or whatever) you have
created the concept in your own imagination.  Ancestry and descent may occur
with or without human perception, but multiple organisms viewed as a single
entity does not.  TAXONOMY IS USEFUL BUT TOTALLY PHONY!
    Why not paraphyletic groups based on common ancestry instead?  You could
name groupings based on individuals OTUs and all of its ancestors; sister
taxa would have almost complete overlap between thier "all ancestors taxon".
This system would be as completely arbitrary as phylogenetic taxonomy using
monophyletic clades, so why hasn't anyone devised a taxonomic scheme using
it?  Because it wouldn't be very useful.
     ALL our conventions in taxonomy, no matter what the system, are devised
for our convenience.  I think we have to be careful about eliminating useful
landmarks like genera, species, and yes even paraphyletic taxa, in the
interest of making taxonomy "less artificial" or "less arbitrary".

>"Why do I sense we've picked up another pathetic lifeform?"

Hey!


LNJ
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Jeffrey W. Martz
Graduate student, Department of Geosciences, Texas Tech University
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