Taxa and Diagnoses

Don Colless donc at ENTO.CSIRO.AU
Tue Apr 8 14:16:39 CDT 1997

     John Trueman wrote learnedly on the distinction between
defining the name of a taxon and identifying its members - an
ancient and thorny topic. However, Mike Dallwitz's point seemed
to be that it is not enough just to delineate a taxon, if it is
ever going to be of any use.
     To my mind it is a waste of everybody's time to erect a
taxon that cannot be efficiently, even conveniently, identified.
It may be of great interest, for a variety of reasons, that some
group seems soundly holophyletic; but that does not mean that it
must be recognised as a named taxon. That is especially true when
it may require the slaughter of a long-loved, useful taxon, on
grounds that may not survive the next run of PAUP - and even
truer if an obligatory category is involved.
     Obviously, if all that is required is to add in some (say)
species that has been looking for a good home, there is no
problem. Likewise, it may be welcomed if grounds are provided to
remove an intruder (of the kind we know so well). However, any
change requires absolutely that the taxon remain reasonably
recognisable by means of a (usually polythetic) diagnosis. And
a responsible taxonomist will provide one.

               *  Don Colless, CSIRO Div of Entomology, *
               *     PO Box 1700 CANBERRA. ACT. 2601    *
               *         (donc at           *
               *     Tuz li munz est miens envirun      *

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