The effects of linkage on the establishment of locally beneficial mutations

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Date(s) - 16/03/2016
11 h 00 min - 12 h 00 min


In subdivided populations, adaptation to a local environment may be hampered by maladaptive gene flow from other subpopulations. At an isolated locus, i.e., unlinked to other loci under selection, a locally beneficial mutation can be maintained only if its selective advantage exceeds the immigration rate of alternative allelic types. Deterministic modeling shows that, if a beneficial mutation arises in linkage to a locus at which a locally adapted allele is already segregating in migration-selection balance, the new mutant can be maintained under much higher immigration rates than predicted by one-locus theory. However, deterministic theory ignores stochastic effects which are especially important in the early phase during which the mutant is still rare. If the beneficial mutation is linked to a beneficial genetic background, it will profit from a hitch-hiking-like effect. If it occurs on a deleterious background, it is doomed to extinction unless it recombines away. Therefore, recombination plays an ambiguous role. Using the theory of branching processes, we obtain exact numerical and approximate analytical results for the invasion probability as a function of the migration and the recombination rate. Some consequences for the evolution of genomic islands of differentiation will be discussed. This talk is based on joint work with Simon Aeschbacher and Sam Yeaman.

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