The Double-Edged Sword Effect of Assortative Mating on Adaptation

Evolutionary rescue links evolutionary biology and ecology by examining how rapid adaptation aids population persistence following environmental change through the integration of genetic and ecological processes. Assortative mating behavior has been observed in a wide range of animals, but its effects on evolutionary rescue have not been fully explored. Here, a simulation is developed that models populations displaying assortative or random mating behavior and adapting to new environments. The results indicate that assortative mating behavior, in comparison with random mating behavior, has a double-edged effect on evolutionary rescue in new environments. Assortative mating behavior reduces the phenotypic variance of a population before environmental change, as well as the rate of accumulation of beneficial mutations when the population size is declining, thus exposing the population to a higher extinction rate and risk than random mating behavior. Concurrently, the assortative mating behavior leads to the rapid accumulation of beneficial mutations when the population size is small and consequently accelerates population recovery, particularly during the middle and late stage of evolutionary rescue. Furthermore, the increased strength of assortative mating can result in an augmentation of the extinction rate and risk of populations, as well as the recovery rate of population size. This study highlights the importance of animal behavior in evolutionary rescue.