There has been a long standing debate in evolution of the possibility of sympatric speciation, that is, speciation between two coterminous populations. Well, here is evidence from some fish of it happening, at least in the first stages, so that genetic differentiation is minimal to non-existent. I don't know how common sympatry is, but I've been to other talks pointing to similar phenomena in other taxa, so I think there has been a detection bias toward allopatry.
But anyway, species concepts are a bugger. The main point is that population differentiation need not always be preconditioned on geographic separation.
I'm wondering if speciation within coterminous populations would be a much slower process allopatric speciation?
"need not always be preconditioned on geographic separation."
Species concepts definitely are a bugger. What is really inscrutable to me is how sympatric populations manage the speciation at all. It must be because of some degree of genetic isolation within a subset of the coterminous populations, no? I have no problem getting a grasp on allopatric, isolated speciation -- the only way I ever learned/ thought it could occur. To me, sympatric speciation is like trying to breed something against itself & get distinctiveness. **((puzzled))**
Thanks for the article.
'destabilizing selection' (i think that's the term) provides a great theoretical example for it. Using length as an example, let's assume a situation in which both the super-long ones and the super-short ones have a lower mortality than the 'average' ones. Assuming that there's a high heritability for length, then mixed mating of super long against super short would result in fewer surviving offspring than those where they assorted according to length in mating habits.
This would provide a way in which a single population would develop mating isolation dependent upon a heritable trait, which I'd think would provide adequate (although imperfect) separation, certainly enough for speciation given a long enough window.