Frank, S. A. 1986. The genetic value of sons and daughters. Heredity 56:351-354.
Bulmer (1986) has recently studied sex ratio evolution under the island migration model. His study was motivated by my statement that as genetic differentiation among isolated patches increases, the predicted proportion of males declines linearly with Pdt, Wright's (1969) measure for differentiation among demes (Frank, 1985, 1986). Bulmer's results show, under the assumptions of his particular model, that the sex ratio is independent of the migration rate for a diploid organism. Since Pdt declines towards zero as the migration rate declines, no migration leads to complete fixation within demes. Bulmer's result suggests that the sex ratio is independent of Pdt. Here I show that different model assumptions are the cause underlying the discrepancy between our results. I also derive an analytic solution for the scenario studied numerically by Bulmer, by applying the genetic value methodology developed in Frank (1986).