Using network analyses to explore the mechanisms underlying female choice of extra-pair mates

Abstract

The classic Darwin-Bateman paradigm of sexual selection states that females gain no benefits by mating with multiple males, and so polyandry should be rare. Recent evidence, however, shows that polyandry is widespread across many animal groups, and that multiple matings by females generate additional episodes of sexual selection, which modulate the total strength of sexual selection. Extra-pair copulations increase or introduce polyandry in mating systems, and its widespread occurrence raises questions about the benefits gained by females seeking additional matings. The main hypotheses to explain extra-pair copulations are that females mate with additional males to ensure fertilization or to obtain indirect benefits either by seeking good genes or increasing offspring heterozygosity. However, restrictions to female behavior as mate guarding by their social partners and distance between territories are seldom taken into account. Sexual interactions connect individuals within populations, forming sexual networks. The structure of these sexual networks may contain information about the underlying processes shaping sexual interactions. In this project, we propose to combine empirical data from extensive fieldwork and a network modeling approach to explore the mechanisms underlying extra-pair copulations in a small passerine bird, the dunnock (Prunella modularis). We propose a model that includes genetic relatedness among individuals, their status in the social groups, possible effects of mate guarding, and spatial distribution of the territories. Results of this model can provide insightful ideas on what factors influence the distribution of extra-pair copulations among individuals in a wild population. (AU)