Hypothetically, I'm thinking of a species of hare that has a range...let's say 300 miles wide. Wouldn't the genes of all the would-be varieties keep criss-crossing across the range ...
Consider a species of hare with a variety that lives above the snowline and a variety that lives below, each adapted to their environments, and suppose them capable of interbreeding. Nonetheless, it might be the case that any cross between the two varieties would be inferior to the below-the-snowline variety in living below the snowline, and inferior to the above-the-snowline variety in living above the snowline. Then natural selection would keep the two types separate, with only a thin band of hybrids between them. The amount of gene flow between the two varieties would be small, and natural selection would keep the two varieties distinct.
Just because there is no
geographical barrier between them doesn't mean that they must blend.
Does that start to answer your question?
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