Not quite sure where I'm trying to go with this (and don't want to derail Little John's thread too far). It's probably one for our band of talented geneticists:

How much (or little) isolation is needed for a true local type to develop in the kind of sustainable manner that allows it to survive over hundreds of years? This might not be too easy a question to answer what with the vagaries of drone-drift but I find the idea of these local ecotypes quite fascinating in the light of what we now know of the effects of inbreeding.