EVALUATING GENE FLOW USING SELECTED MARKERS - A CASE-STUDY

The extent to which an organism is locally adapted in an environmental pocket depends on the selection intensities inside and outside the po cket, on migration, and on the size of the pocket. When two or more lo ci are involved in this local adaptation, measuring their frequency gr adients and their linkage disequilbria allows one to disentangrle the forces-migration and selection-acting on the system. We apply this met hod to the case of a local adaptation to organophosphate insecticides in the mosquito Culex pipiens pipiens in southern France. The study of two different resistance loci allowed us to estimate with support lim its gene flow as well as selection pressure on insecticide resistance and the fitness costs associated with each locus. These estimates perm it us to pinpoint the conditions for the maintenance of this pocket of adaptation as well as the effect of the interaction between the two r esistance loci.