Re: Classification (was Panduro) -Reply

[cfonda@sentientconsult.com]

Dave wrote:

>If two fish cannot form fertile hybrids they are, BY DEFINITION, different
>species.  If they can form fertile hybrids, one must next ask if they do
>this in nature.  If they do not, they are different species.  If they
>exchange genetic material in nature, they are the same species (roughly).

With one exception, for two species to be genetically compatible (produce
viable, fertile offspring when cross-bred) and still be separate species is
very rare and requires massive ecological isolation.  The exchange of
genetic material between the two in the wild must be absolutely zero (not
approximately zero) for them to be classified as truly distinct species.
This usually involves massive geological separation... ie -- mountain
ranges, deserts, or oceans separating the species.  The S.A. waters are
fairly interconnected (especially when flooding is accounted for...) and
some population interchange probably occurs, with occassional
interbreeding.  The one case where separate species may be declared in
spite of genetic compatibility without extensive research into the habitats
of the species is when the two species show significant anatomical
differences (more than simply outside appearance).  Most modern taxonomists
rely primarily upon anatomical differences for the declaration of species,
which has the advantage of avoiding the need for cross-breeding experiments
and in-depth habitat study.  (NOTE:  Some of the finer points of species
classification and declaration have historically been, and continue to be,
subjects of controversy within the scientific community.)

--Cliff



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