Dispersal alters the nature and scope of sexually antagonistic variation

Abstract

Intra-locus sexual conflict, or sexual antagonism, occurs when alleles have opposing fitness effects in the two sexes. Previous theory suggests that sexual antagonism is a driver of genetic variation by generating balancing selection. However, these studies assume that populations are well-mixed, neglecting the effects of spatial subdivision. Here we use mathematical modelling to show that limited dispersal can fundamentally change evolution at sexually antagonistic autosomal and X-linked loci due to inbreeding and sex-specific kin competition. We find that if the sexes disperse at different rates, kin competition within the philopatric sex biases intralocus conflict in favour of the more dispersive sex. Furthermore, kin competition diminishes the strength of balancing selection relative to genetic drift, reducing genetic variation in small subdivided populations. Meanwhile, by decreasing heterozygosity, inbreeding reduces the scope for sexually antagonistic polymorphism due to non-additive allelic effects, and this occurs to a greater extent on the X-chromosome than autosomes. Overall, our results demonstrate that spatial structure is an important factor in predicting where to expect sexually antagonistic alleles. We suggest that observed interspecific and intragenomic variation in sexual antagonism may be explained by sex-specific dispersal ecology and demography.

Is the X chromosome a hot spot for sexually antagonistic polymorphisms? Biases in current empirical tests of classical theory

“…where s f , s m , h f , and h m are the selection and dominance coefficients for the SA locus (table 1; electronic supplementary material, appendix A). We note that inbreeding, population structure, and overlapping generations can somewhat modify these criteria for balancing selection, though we do not consider such effects here (see [47][48][49]). Criteria for maintaining SA polymorphisms are identical for X-linked and autosomal loci (i.e.…”

Dominance reversals: the resolution of genetic conflict and maintenance of genetic variation

“…Below, we provide a biophysically explicit proof-of-concept for what a dominance modifier could look like and analyse its evolution using forward-time individual-based population genetic simulations (box 1; electronic supplementary material S2). Our example is a starting point for a theoretical approach that would be useful in assessing both of these outstanding issues, as well as whether antagonistic selection on a phenotype can maintain genetic variation [109], whether dominance reversals compete with gene duplications [110] or other forms of resolution, and evaluating patterns in empirical data [78].…”