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Re:Species or not species in crypts

Steve Pushak wrote:

>what do you think about the possibility that Crypts evolved species
>differentiation (the un-ability to mix species) as an pro survival
>adaptation? This was proposed by Paul Krombholz on the Crypts list
>recently... Maybe Paul might explain it better than I did. I remember
>you have a background in botany/forestry.

One of my main points was that two different populations that have diverged
because they have been separated geographically, will, if they do come into
contact later, evolve barriers to interbreeding bacause hybrids produced by
interbreeding do not survive well.  Each population has become specialized
for a certain habitat, and the hybrids are not well suited to live in
either parental habitat.  Thus, there is a penalty for interbreeding.  If
there is a penalty for interbreeding, then there will be selection for
varieties that are less likely to interbreed with members of the other

The geneticist, Theodosius Dobzhansky, was able to select for completely
effective barriers to interbreeding between two varieties of Drosophila
melanogaster that only differed in a single gene, and which, initially
interbred with no discrimination.  He did it by removing from the
population all offspring of crosses between the two varieties each
generation and leaving all offspring resulting from crosses within the same
variety. Once the barriers were established, Dobzhansky had, in effect,
created two species.   It took him 160 generations.  For fruit flies, that
is a little over three years.

I suspect that many of our Crypts are varieties from populations that have
diverged, but have not later come into contact and have not evolved
barriers to interbreeding.  Thus, although they may be quite different,
they can still interbreed, and this makes deciding whether or not they are
the same or different species quite difficult.

Paul Krombholz, central Mississippi, enjoying dry, clear, cool Canadian