A friend of mine told me that in California there are different subspecies of salamanders where interbreeding is impossible. He said, for instance, that subspecies A can breed with subspecies B, And B can breed with C, But A cannot breed with C. I find this rather odd. My question is this:

If A can breed with B, And B with C, Shouldn't it be possible for A to breed with C? If A and C don't breed in nature, I would think it would have more to do with preference and not physical ability.

Please help us. TIA