Sex ratio evolution when fitness and dispersal vary.

In a heterogeneous environment, when the fitness of males and females are differently influenced by habitat quality, habitat-dependent sex ratios may evolve to favor the production of the sex that benefits more (or loses less) from the local habitat. Similarly, sex-biased dispersal favors the evolution of habitat-dependent sex ratios. The present study documents the convergence stable sex ratios expected in the presence of sex-specific fitness gains when dispersal is partial, sex-biased or costly, using a simple model with patches of two qualities. Results show that partial dispersal reduces the sex ratio bias expected with sex-specific fitness gains. The direction of the sex ratio bias can be reversed by sex-biased dispersal or the existence of sex-specific dispersal costs, provided that fitness gains for the two sexes are not too different. The reversal of the sex ratio bias is more readily observed when sex-specific dispersal rates are opposite and extreme. Both dispersal and fitness gains, especially when they are sex-specific, should thus be considered when making predictions about sex ratio evolution in a heterogeneous environment. [ABSTRACT FROM AUTHOR]