What would most likely cause a decrease in Fst from 1 to 0 in two neighboring populations?

A decrease in Fst from 1 to 0 indicates that two populations, which were previously completely diverged (with no shared alleles) are becoming more genetically similar. This change is most commonly caused by migration, which introduces individuals from one population to another, resulting in gene flow. When individuals migrate between populations, their alleles can mix with those of the residents, increasing genetic similarity over time.

In genetic terms, Fst is a measure of population differentiation due to genetic structure; an Fst of 1 indicates complete differentiation (no shared alleles) while an Fst of 0 indicates no differentiation (complete sharing of alleles). As migrants contribute their genetic material to the recipient population, the overall genetic composition of both populations converges, thus reducing Fst toward 0.

Migration can result from various ecological or behavioral factors, such as seeking resources, changes in habitat, or variability in environmental conditions, thereby playing a crucial role in the evolution of species and the structure of populations. In contrast, genetic drift and natural selection can affect allele frequencies, but they do not generally lead to homogenization between two distinct populations in the same manner as migration does. Mutation contributes new alleles within populations but does not directly facilitate gene flow between