Which process is counteracted by gene flow, impacting speciation?

Gene flow refers to the transfer of genetic material between populations, which helps to maintain genetic diversity and can hinder the process of speciation. When individuals migrate between populations and interbreed, they introduce new alleles into a population, which can lead to the homogenization of allele frequencies across different groups.

The correct answer emphasizes that gene flow counteracts the tendency of populations to diverge genetically due to differing environmental pressures or genetic drift. When allele frequencies remain similar due to gene flow, the populations do not become as distinct from one another and are less likely to evolve into separate species. This means that gene flow can effectively reduce the divergence expected in populations that are undergoing speciation by keeping them genetically similar.

In contrast, processes like genetic drift and natural selection may lead to differences in allele frequencies within isolated populations, promoting speciation rather than counteracting it. Divergent evolution specifically involves populations developing distinct traits due to adaptation to different environments, a process that can be mitigated by consistent gene flow.