Natural selection has a positive feedback loop that means increased frequency of certain alleles in a population and there may be a negative feedback loop decreases the frequency of others.
Of course. The black feathered population has more alleles for black feathers, and probably lots of homozygosity for black feathers at the feather loci too, while the grey population has more alleles for grey feathers and the same genetic situation. The black feathered population has correspondingly fewer alleles for grey feathers, which will eventually decrease to zero as reproductive isolation continues, and the grey population for black feathers. This ought to be elementary my dear Watson, but evo theory manages to complicate the simplest things.
And of course it makes sense to categorize sexual selection as a type of natural selection, just as I've argued that geographic isolation is a form of natural selection too, as it isolates some particular collection of alleles and breeds them together to produce a new phenotype, which is all any selective process does.
And again, all this is within microevolution, it's ridiculous to make the arbitrary fact that the two populations don't interbreed into "speciation." It's nothing but two variations that happen to separate, and may possibly have a genetic barrier to interbreeding although that is not necessary. If it does it could be because of the greater homozygosity of the characteristic feather color in each population and the more fixed loci each has the less ability to combine the two.
Edited by Faith, : No reason given.
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