Mating Systems and Evolutionary Rescue

Animal mating systems are hugely diverse, ranging from species where mating is essentially random to those exhibiting complex systems of mate choice by one or both sexes. While polygyny and mate choice are known to alter adaptation and persistence in a changing environment, there has been little exploration of the ways that adaptation and evolutionary rescue are modulated by other types of mating systems. We developed an individual-based model that allows random mating, female-only choice, and mutual mate choice to be compared between monogamous and polygynous frameworks and used it to explore how mating systems influence adaptive response, loss of heterozygosity, and extinction risk under worsening environmental conditions. We find that mating systems interact with population size in determining extinction risk: mate choice under polygyny lowers effective population size, small polygynous populations with either mutual or female-only mate choice lose heterozygosity quickly and so face higher extinction risks than randomly mating populations. However, in larger populations where inbreeding and genetic drift are less important, mate-choice-based polygynous systems enhance evolutionary rescue by allowing better-adapted males to dominate reproduction, accelerating adaptation and increasing resilience to environmental change. Among polygynous systems, female-only choice leads to slower loss of heterozygosity and facilitates population resilience better than mutual mate choice. These findings demonstrate that mating systems can critically shape a population's ability to adapt to environmental change and alter extinction risks, emphasizing the need to consider mating systems in designing effective conservation strategies.