arbitrariness

Barry Roth barry_roth at YAHOO.COM
Thu Jul 3 17:59:16 CDT 2003


I suppose you can't be blamed for offering a cheerful, positive (if hypothetical) example.  But quite often the result is that later, more penetrating studies falsify monophyly based on early "gestalt" choices.  Or suppose there are multiple "clearly externally visible morphological differences" and reasonable classical taxonomists can debate about the weight to give them, respectively.  All you really seem to be describing is the process of seat-of-the-pants taxonomy as she has been practiced for decades.  And for every instance in which subsequent studies falsify gestalt-based monophyly, to maintain the traditional name and rank assigned to that gestalt-based group is simply to mislead users of the taxonomy.

I'm reminded of the time I showed my mentor an analysis I had done in which the nominal study group (call it, oh, Helminthoglypta) parsed into three nested taxa, of which only one, because it contained the type species of Helminthoglypta, could reasonably be called Helminthoglypta. I applied existing, erstwhile subgeneric but now generic, names to the other two taxa.  My mentor looked at it, nodded over the results, and then handed it back to me remarking, "ah, yes, but they're still all helminthoglyptas."  Sigh.

Barry

"Nico M. Franz" <nmf2 at CORNELL.EDU> wrote:
[...] I select the one that is
associated with the clearest externally visible morphological differences
(what evolutionary taxonomists tend to call "gestalt"), and maybe an
interesting biological observation I made in the field. Now suppose that I
did this 25 years ago, and by now more inclusive studies have not only
confirmed the monophyly of my genus, but also generated a whole bunch of
noteworthy evolutionary results for members within it. So basically now we
have a communication vehicle that exclusively delimits not only a
monophyletic group, but also a load of morphology, cladistic hypothesis
testing, and unique evolutionary history.


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