[Taxacom] Usefulness (of "semi-holophyly")

Barry Roth barry_roth at yahoo.com
Thu Dec 16 17:42:40 CST 2010

Dear Ken,
With respect to your question, I would only say that many end-users of a classification will not have the full classification on paper or screen in front of them.  Imagine a pharmacologist asking a taxonomist what group's taxa to search for species that produce a certain phytochemical.  For the taxonomist to be able to recommend a holophyletic taxon is at least marginally more efficient that having to specify a paraphyletic taxon _plus_ its ex-group.
This may be putting a pretty fine point on it, but "usefulness" depends partly on context.

--- On Wed, 12/15/10, Kenneth Kinman <kennethkinman at webtv.net> wrote:

From: Kenneth Kinman <kennethkinman at webtv.net>
Subject: [Taxacom] Usefulness (of "semi-holophyly")
To: taxacom at mailman.nhm.ku.edu
Date: Wednesday, December 15, 2010, 6:44 PM

Hi Barry,
       This raises the following question in my mind.  Would the
increased efficiency (for that type of search) of holophyly over
paraphyly also apply to holophyly over "semi-holophyly"?  
       In my classifications, I render my paraphyletic taxa
"semi-holophyletic" (or "semi-paraphyletic", another way to say the same
thing).  I do this not only by labelling and coding the paraphyletic
group as such, but also placing my {{exgroup}} markers at the
appropriate place within the paraphyletic group (rendering it
holophyletic in an informational sense).        
      It has always seemed to me that annotating my paraphyletic taxa in
these explicit ways, I maintain of the advantages of holophyly.  And you
get the added advantages of ancestor-descendant information which many
workers (like Richard Zander) find so valuable.  It seems like this is
how one can get the best of both.  Having to annotate classifications
seems like a small price to pay for all the advantages (and avoiding
many disadvantages).    
         -------Ken Kinman         
P.S.  Purely cladistic classifications (especially at higher taxonomic
levels) often lead to frustration because: (1) lack of information
prevents an accurate phylogeny; and (2) more complete information can
yield classifications that are overly complex, confusing, and even
unstable (especially when new information cast serious doubt on
previously available information).  After over 30 years doing this kind
of classification, my experience is that an occasional paraphyletic
taxon (rendered semi-holophyletic) can make classifications less
complex, more useful, as well as anageneticallly more informative.  

Barry Roth wrote:
      Because of organic evolution (remember him?), it's a plausible
prediction that a newly discovered character-state in one member of a
holophyletic group will also be found in other members of that group. 
The same is true for a paraphyletic group, but the character-state may
_also_ be expected in the excluded taxa that make the group
paraphyletic.  So holophyly is a more efficient way of circumscribing
groups when you're interested in that type of search.   


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