In a species of birds, wing size is controlled by a single gene that has only two alleles. The same species lives in two different forests. In one forest, the trees have less foliage and the birds' nests are more susceptible to predation. The large-winged birds are able to flee more quickly. In the other forest, the birds with smaller wings are more obscured from predators. Which of the following best describes the species of birds in the different forests? A) Selective pressures can cause alleles that are adaptive in one environment to become deleterious in another.
B) The species will eventually develop an intermediate wing size in both populations.
C) The alleles of both populations will undergo directional selection to have the same allele frequencies.
D) If genetic diversity and allele frequencies differ, the species will risk decline.