exactly what is a species?

[tom dibenedetto]

To quote Tremaux (1865) " Of definitions of species, there are as many
as there are naturalists". As Nelson (1989) noted, " They (species
concepts) are a perennial, if not eternal, topic of discussion and
dispute about whose distinctions will prevail in the science....".
        The great majority of definitions seem to
arise from the ranks of evolutionary theorists; those who attempt to
frame their species concept around their own view of what is of
fundamental importance in terms of evolutionary processes. In systematics
however (which is, of course the study of biological diversity), I think it
fair to say that "species" has usually referred to the minimal
diagnosable unit of diversity. This was certainly the original definition
(dating from the time when there really was no process being theorized
about), and I personally feel that it rests with systematists, within
such a context, to define the concept. All the talk about gene flow and
reproduction and allelic differences etc. can and should contribute to
explanations of species, but not necessarily to the basic definition of
the concept.

Tom diBenedetto
Fish Division
University of Michigan Museum of Zoology