speciation and peripheral isolates

John Grehan jrg13 at psu.edu
Thu Jun 10 04:35:32 EDT 1999

>>  So what is speciation? When a peripheral isolate looses breeding touch
>with the heartland, it may or may not run with selection under changing
>conditions until it can no longer interbreed with other populations of the
>same immediate ancestry. It steps into a new niche and becomes a new species.

This is only one hypothesis about speciation. Panbiogeographic studies
suggest that differentiation often occures over wide areas relative to the
ancestral range without involving peripheral isolates.

>>  We need the concept of subspecies, with names, in order to identify and
>study the interesting peripheral populations that have diverged from the
>species norm.

Such ranks could also be applied to entities that are not peripheral, but
vicariate with respect to other members of the species.

>>  As you see, I think punctuated equilibrium theory is just great and each
>equilibrium is a subspecies or species.

Since panbiogeographic analysis does not support the prevalence of
peripheral isolation required under the punctuated equilibrium model.
the model appears not to be very applicable to evolution in general.

My apologies for not making any direct reference to Lepidotpera in
responding to comments listed by others.

John Grehan

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