Final answer:
Migration can lead to changes in allele frequencies and, over time, may result in the formation of new species through allopatric speciation, due to geographical separation and varying environmental factors.
Step-by-step explanation:
Migration affects populations by causing changes in allele frequencies and occasionally leading to the differentiation into distinct species through a process called allopatric speciation. In a geographically continuous population, gene flow maintains homogeneous allele frequencies across a species' range. However, when a population becomes geographically discontinuous, the interruption in gene flow can result in populations evolving separately, leading to divergent allele frequencies at various loci.
Over time, factors like environmental conditions, mutation, and genetic drift can affect each isolated population differently, potentially fostering distinct adaptations that contribute to speciation. This divergence can become so pronounced that interbreeding between the two populations is no longer possible, ultimately leading to the formation of new species.