The fixation of locally beneficial alleles in a metapopulation

Extinction, recolonization and local adaption are common in natural spatially structured populations. Understanding their effect upon genetic variation is important for systems such as GMO management, or avoidance of drug resistance. Theoretical studies on the effect of extinction and recolonization upon genetic variance started appearing in the 1970’s, but the role of local adaption still has no good theoretical basis. Here we develop a model of a haploid species in a metapopulation in which a locally adapted beneficial allele is introduced. We study the effect of different spatial patterns of local adaption, and different metapopulation dynamics, upon the fixation probability of the beneficial allele. Controlling for the average selection pressure, we find that a small area of positive selection can significantly increase the global probability of fixation. However, local adaption becomes less important as extinction rate increases. Deme extinction and recolonization has a spatial smoothing effect which effectively reduces spatial variation in fitness.