International audienceThe relation between mating system and sex-biased dispersal has been debated for three decades. However, the relative importance of the processes involved in this relation remains poorly known. In this study, we paid special attention to kin competition. We built an adaptive individual-based model fixing three mating systems (monandry, polyandry, monogamy) in a metapopulation, and allowing dispersal across patches to evolve independently for males and females. Our simulations showed that a difference in the number of mates can determine the evolution of sex-biased dispersal. Dispersal appears male biased under monandry and polyandry, but balanced under monogamy. By contrast, we showed that inbreeding can influence but does not promote sex-biased dispersal, and that the primary sex ratio does not qualitatively affect the evolution of sex-biased dispersal under monandry and polyandry. These results are driven by the interaction of two factors: the variation in reproductive success between patches in the metapopulation and kin competition. These two factors are influenced by the mating system, which modifies both the competition for access to partners and the mean relatedness between individuals. To ascertain that kin competition actually drives sex-biased dispersal, we made simulations with destruction of any genetic structure in the metapopulation, and we found that in this case dispersal was not sex biased
In many hermaphroditic flowering plants, self‐fertilization is prevented by self‐incompatibility (SI), often controlled by a single locus, the S‐locus. In single isolated populations, the maintenance of SI depends chiefly on inbreeding depression and the number of SI alleles at the S‐locus. In subdivided populations, however, population subdivision has complicated effects on both the number of SI alleles and the level of inbreeding depression, rendering the maintenance of SI difficult to predict. Here, we explore the conditions for the invasion of a self‐compatible mutant in a structured population. We find that the maintenance of SI is strongly compromised when a population becomes subdivided. We show that this effect is mainly caused by the decrease in the local diversity of SI alleles rather than by a change in the dynamics of inbreeding depression. Strikingly, we also find that the diversity of SI alleles at the whole population level is a poor predictor of the maintenance of SI. We discuss the implications of our results for the interpretation of empirical data on the loss of SI in natural populations.
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