Mahlon G. Kelly mgk at darwin.clas.Virginia.EDU
Sat Sep 9 10:54:49 EST 1995

watters at tasman.cc.utas.edu.au  writes:
> Hi
> There's probably an elementary answer to this question which occured to me last
> night watching a documentary on Darwin's life and times. Say you have
> two species, B and C, who have a common ancestor, A, from which they
> both developed/evolved independently over many years. At what point
> do B and C, B and A, and C and A lose the ability to mate succesfully?
> Has anyone modelled such a phenomena?
> (Thinking back to my biology days, the ability to mate seemed to be
> involved in the definition of what a species was/is). Anyway, I'd
> appreciate any thoughts on this topic (or pointers to appropriate
> references). Especially from a genetic programming p.o.v.
> Cheers,
> Paul
> --
> +-----------------------------------------------------------------------+
> | Paul A Watters  (watters at utas.edu.au)                                 |
> | Department of Psychology, University of Tasmania, AUSTRALIA           |
> | Hay un tiempo para cada cosa, y un momento para hacerla bajo el cielo |
> +-----------------------------------------------------------------------+

That is not an easy question to answer. It depends on the
generational time, the length of time they have been separated,
the size of the populations, the degree of difference in
selection between the isolated populations, and more. There
have been quite a few instances in which two species that
seemed different, and were given separate names by taxonomists,
were found to interbreed perfectly well. There are many
instances in which infertile hybrids are produced. And there
are many situations in which fertile hybrids might be produced
but are not because the species breed in different places, at
different times, etc. 

Even more puzzling is how one defines a new species as it
appears over time in the fossil record, since, presumably,
there is no distinct point in time in which the species is
"new" genetically.
Associate Professor (Emeritus)
University of Virginia
mgk at darwin.clas.virginia.edu

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