Bob,
 In addition to the example of humans consider canines as well.  Just
based on skeletal morphology I would consider a toy poodle a distinct
species from the great dane or the english bulldog.  It is only when we
consider all morphological variants (include my beloved mutts in here) and
the physiology/biochemistry/molecular genetics that we know about canines,
that we conclude they are a single species.  The same can be said for most
domestic animals that we have selectively bred...pidgeons, cattle, sheep,
chickens, etc.
  At the World Congress of Malacology a paper was presented by Barnes and
Weight on the "species" Codakia orbiculata (Montagu).  Based on shell
morphology this organism seems to be one species.  When you factor in
allozyme and mitochondrial DNA sequence analyses they find that it is
probably 5 separate species.  Two points that I would make from this.  We
do need to make use of all the information that is available when
describing a new taxon...morphological, biochemical, and paleontological.
Secondly, we should consider the names of organisms as hypotheses, they
are our best guess as to what constitutes a new taxon, always able to be
challanged and modified as new data comes to light.
 
Charlie
******************************************************************************
Charlie Sturm, Jr
Research Associate - Section of Invertebrate Zoology
                     Carnegie Museum of Natural History
Assistant Professor - Family Medicine
 
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