[Taxacom] Usefulness (was: Defining polyphyly)

[John Grehan]

If course from my perspective Curtis did not. A group that is defined by
the exclusion of some members of its clade does not seem 'natural' in
any way that reflects that nature of hypothesized entities. It would be
like saying humans are all those with unique features x, y, and z, but
excluding anyone from New Zealand (although to some that might be
perfectly natural!).

John Grehan

-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu
[mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Kenneth Kinman
Sent: Wednesday, December 15, 2010 12:28 PM
To: taxacom at mailman.nhm.ku.edu
Subject: [Taxacom] Usefulness (was: Defining polyphyly)

Hi Curtis,  
      You hit the nail right on the head again.  Paraphyletic groups are
just as natural as  holophyletic groups.  And "usefulness" is therefore
the more appropriate subject to debate.  I think Richard Zander's
arguments support the usefulness of paraphyletic taxa, not only in that
they include important information beyond mere sister group information,
but also by demonstrating how focusing too much on sister groups can
lead to false conclusions (which are definitely not useful).        
         Including both kinds of information in a classification is
therefore not only more useful in an informative sense, but they also
complement one another by helping to avoid false conclusions (which can
be very destabilizing to a classification).  You get more information
and less disinformation, two very useful qualities.       
              ----------Ken Kinman                    
----------------------------------------------------------
Curtis Clark wrote:       
On 12/15/2010 5:09 AM, John Grehan wrote:  There's the hinge of it all -
whether paraphyletic groups are any more 'natural' than those that are
polyphyletic.
      A paraphyletic group can be specified by synapomorphies (a set for
the stem group and other sets for the exgroups), so it is as "natural"
as a monophyletic group. The question is rather, is it useful. And
that's where the disagreement seems to center. 
Curtis Clark              


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