Consanguineous mating, specialization, and the environment: how multiple variable interactions affect the evolution of dioecy.

Premise: The evolution of dioecy in plants is usually modeled as a consequence of self-fertilization. While increased seed and pollen production and dispersal patterns of specialized unisexuals have been examined, mating among relatives and interaction effects have been largely ignored. Here, we examine multiple variables simultaneously providing a more ecologically realistic set of conditions favoring the evolution of dioecy. •

Methods: We developed two complementary models to explore the evolution of dioecious plants. In both models, we examined the effects of inbreeding, compensation, and specialization on unisexual invasibility and were able to directly measure the influence of related matings on such a system. •

Key Results: Our results support previous studies indicating dispersal specialization, consanguineous mating, and inbreeding depression facilitate the evolution of dioecy. However, our results suggest that it is the interaction effect of multiple forces acting simultaneously that allows for unisexual invasion at thresholds and frequencies witnessed in nature. Additionally, our results suggest that subdioecious populations often result, and depending on population conditions, dioecy evolves at different rates, lending importance to the ecological and life history conditions of the species. •

Conclusion: Mating among relatives significantly enhances the invasibility of a unisexual mutant into a hermaphroditic population and lowers the levels of inbreeding depression required for invasion than previously reported conditions for unisexual invasion especially, if we consider multiple pressures simultaneously.