Final answer:
Microevolution in the dove population could be caused by natural selection favoring long tails, genetic drift through random changes in allele frequencies, or the founder effect as a result of a few individuals starting a new population with different genetic makeup.
Step-by-step explanation:
In the context of microevolution, a small group of long-tailed doves migrating to a new forest and subsequently showing an increase in the population could be due to several factors including natural selection, genetic drift, or the founder effect.
Natural selection might favor long tails if they provide some advantage in the new environment, like better mate attraction or improved flight capabilities. Conversely, genetic drift could lead to the increase if, by chance, the migrating doves carrying the long-tailed traits reproduce more successfully. The founder effect is another possibility, which occurs when a new population originates from a few individuals—any traits present in the founders can become more common in their descendants regardless of their adaptive value.
Habitat isolation may also play a role if the long-tailed doves no longer mate with the original population, leading to reproductive and genetic independence.