Island Model of Migration

Consider a small island adjacent to a mainland. Given that the mainland population is likely to be much larger than that of the island, movement of individuals (migration) from the mainland to the island has a large impact on the composition of the island gene pool, whereas movement from the island to the mainland contributes relatively little to the mainland gene pool. Under these conditions, the migration rate (m) can be estimated as the fraction of newly-arrived immigrants from the mainland in the island population. The model therefore considers the effect of m on q_i, where q_i and q_m are the initial allele frequencies on the island and mainland, respectively.