Re: What is a species?

From: george murphy (gmurphy@raex.com)
Date: Thu Feb 01 2001 - 10:55:16 EST

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    Keith B Miller wrote:

    > >Pray, what is a species?
    > >
    > >This is a very serious question.
    >
    > There are several different definitions. The standard biological species
    > definition is "a population of interbreeding individuals that is
    > reproductively isolated from other such populations under natural
    > conditions." This provides a good theoretical definition but is often
    > difficult to apply in real situation in the field and is obviously not
    > applicable to the fossil record.
    >
    > In practice what is commonly used is a morphological definition. In this
    > case, anatomical variation within a species is less than that between
    > species. Maintaining anatomical distinctions between coexisting
    > populations (or those in direct contact) would seem to require a degree of
    > genetic isolation sufficient to prevent the mixing of gene pools (ie they
    > are reproductively isolated). the existence of populations (or fossil
    > collections) with statistically distinct anatomies is thus considered a
    > basis for species designation.
    >
    > There are now also those who advocate using genetic divergence as a
    > criteria for recognizing species.

            Is there any evidence that there is a specific amount (even
    approximately) of genetic divergence which results in reproductively isolated
    populations? I.e., is it likely that there is a 1-1 correlation between
    criterion 3 and criterion 1?

    Shalom,

    George



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