Three factors aid the divergence of the gene pools of two geographically separated populations. Explain each of these factors that causes allopatric populations to become sympatric. What is the "founder effect?"
First, there is a high probability that the two populations have different initial gene frequencies. Thus, selection pressure will have different material to work with resulting in increasing differences between the populations. When a small population founds a geographically isolated colony, the probability of this small break-away population having very different gene frequencies than the mother group is extremely high: This is a type of genetic drift called the founder effect. Second, the two populations will experience different mutations, again, providing selection with two different sources of raw material on which to act. Third, the two populations will likely experience different environmental selection pressures.
