Once two populations of a species have become allopatric with some barrier preventing gene flow between them, the two populations are free to diverge genetically. One mechanism for divergence that is thought to result in rapid divergence is sexual selection.

a. Why is sexual selection likely to result in more rapid changes in phenotype than typical natural selection in the same population?

b. Why is sexual selection likely to result in more rapid speciation than natural selection in the same population?