THE INFINITE ISLAND MODEL WITH SEX-DIFFERENTIATED GENE FLOW

Identity measures are derived for the infinite island model with separ ate sexes and sex-differentiated contribution to gene flow. The concep t of effective migration rate, m(e), is introduced, which describes th e genetically effective flow when sexes migrate at different rates, wh en females migrate as mated or when sexes differ in ploidy, as in the case of X-linked genes or haplodiploidy. The notion of m(e) allows the different cases to be described by the common equation F = 1/(1+4N(e) m(e)). When the reproductive sex ratio differs from unity, migration o f the rarer sex entails more effective gene flow than migration of the common sex. With female dispersal after mating, as well as with ploid y differences, the effective migration rate departs from the census ra te, and migration of diploids and/or mated females normally homogenize s the population more than the migration of haploids and unmated femal es, as expected. This difference between the effective gene flow and t he number of migrants contributes to a possible discordance between di rect and indirect estimates of dispersal. At the same time, the expect ed difference in genetic differentiation between autosomal and X-linke d loci opens the possibility for revelation of sex-differentiated migr ation, which may help resolve such instances.