Dispersal and the sex ratio

It has been shown by Fisher that a 1:1 sex ratio should be evolutionary stable as there would otherwise be a frequency-dependent advantage to the rarer sex 1 . Hamilton pointed out that Fisher's argument depends on the assumption of population-wide random mating, and showed that a female-biased sex ratio was expected in a model in which mating occurred within small local subgroups before population-wide dispersal of mated females. We consider here the sex ratio under some other models of dispersal in a geographically structured population.