"Guttman,Burton" <GuttmanB at evergreen.edu> wrote, in part:

> The only species definition that makes any sense is one
> based on the question of interbreeding. (Irregular or complicated
> interbreeding, or interbreeding between groups that aren't sister species,
> just means that evolution is still in process and that nat!
> ure doesn't always allow us humans to have neat, orderly classifications
> for everything.) Whether two organisms will mate depends on complicated
> matters of appearance and behavior, which can't be read off a DNA
> sequence....

I haven't read the original work, but I think the suggestion was that the
DNA differences WOULD in fact preclude interbreeding. Back in my coral reef
ecologist days, there was a lot of argument about this sort of thing vis a
vis coral species, and someone - I think it was Jeremy Jackson, but I'm not
sure - coined the term "cryptic species" for this situation where multiple
species in effect "hide" under a single pretty similar phenotype.

I guess I, like Burton, am mostly comfortable with the "biological species
concept" (sensu Mayr), but if there are genetic variations within what we
think of as a single species, variations which produce distinct
non-interbreeding populations, then aren't they separate species? Why are we
calling something a species in the first place? Isn't it just a convenient
way of organizing the world around us? It's not as though "species" has any
real non-arbitrary meaning, but if the birds can tell the difference ("Hey!
Your DNA is too different from mine! I'm not breeding with YOU!"), then
isn't there a difference?

-Josh Hayes, josh at blarg . net