Sex ratio theory in geographically structured populations.

Equilibrium sex ratios have been determined analytically under Wright's island model in order to determine the effect of population structure with limited dispersal. When mating occurs before dispersal, the dispersal rate has little or no effect, and the equilibrium sex ratio remains the same as under complete dispersal (the standard model of local mate competition). With dispersal before mating, there is a bias towards the sex with the higher dispersal rate due to lower competition between sibs of that sex.