[Taxacom] This week's paraphyly discussions

Stephen Thorpe stephen_thorpe at yahoo.co.nz
Mon Dec 20 00:09:47 CST 2010

yes, they may have been taught that "paraphyly is bad", but that means they must 
have stupid teachers, because paraphyly is bad only when you don't know you have 
it, but if you flag a taxon as paraphyletic, then there is no problem ...

From: Kenneth Kinman <kennethkinman at webtv.net>
To: taxacom at mailman.nhm.ku.edu
Sent: Mon, 20 December, 2010 6:44:38 PM
Subject: [Taxacom] This week's paraphyly discussions

Hi Stephen, 
       That is what I like about the discussions this
week. In spite of disagreements about the more minor points (and those
will always be inevitable and often stimulate valuable new research), we
have been getting back to some of the most important points (especially
about paraphyly). That paraphyletic taxa are not unnatural and many
people find them very useful. Plus your latest point that attempts to
eliminate the most important useful ones can be so damaging that it
becomes very counterproductive (especially in the long run). Once even
more people realize these main points (especially younger biologists
have been taught that paraphyly is bad), we can then debate subjects
which are more productive---such as which paraphyletic taxa are the most
useful and worth keeping. Such debates would be truly productive and
certainly far less acrimonious than the debate has been between "some
paraphyly" and "no paraphyly at all" (over the last 30 years or so).
         And I agree with you that some paraphyletic taxa
are very hard nuts to crack, but also agree with Curtis that we are
slowly cracking a lot of those nuts. My view has always been that the
difficult paraphyletic groups should remain paraphyletic as long as we
can't reliably "crack them" phylogenetically (which can be a very long
time).  Once we do crack them sufficiently, then we can debate whether
they are useful enough to keep paraphyletic or whether they should be
abandoned and cladified. For example, once there was sufficient
information to cladify Thecodontia, I abandoned it and further cladified
that portion of the tree of life (within Reptilia). However, although
some taxa like Class Reptilia (as a whole) have also been largely
"cracked" (except for turtles), it just has too much value and history
to abandon in our lifetimes (if ever).  And although we have begun to
crack Kingdom Protista, I doubt that I would ever want to abandon it
either.  Some of these higher level paraphyletic taxa are definitely
worth fighting for, while others (like Thecodontia) should be abandoned
when it is useful to do so.  I don't think anyone will regret the
abandonment of Thecodontia, but Reptilia and Protista are a whole
different matter.  We have to pick our battles carefully.  
       Which finally brings me to the 11-Kingdom
classification that Tony gave us a weblink to. Interesting, but it seems
overly split to me. I've never even heard of the names Euexcavatae or
Eukaryomonadae before, and they and the more familiar taxa
Discicristatae and Rhodophytae all seem particularly minor in terms of
diversity (of either form or numbers of species) to compare with major
taxa like Metazoa or Metaphyta. And it's far easier to learn and
remember 4 Kingdoms of Eukaryota compared to 11 (which include taxa
hardly anyone has ever heard of). And it just doesn't strike me as a
very balanced classification, even if all the proposed Kingdoms were
well-known. If one is proposing Kingdoms like Euexcavatae and
Eukaryomondae, it is clearly going to be regarded as oversplit and it
will never gain acceptance. Overemphasizing differences just leads to
oversplitting which unnecessarily complicates a classification.  Ernst
Mayr in particular always emphasized the importance of balance (as well
as usefulness) in classifications.  And at such high taxonomic level,
these classifications are going to affect a very large number of
Stephen wrote: 
          to return to the main point of all this,
paraphyletic residues are not as big a problem as the instability
typically caused by attempts to eliminate them ... 


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