Monogynous mating strategies in spiders

Abstract

To understand the evolution of mating systems, we need to consider why reproductive strategies differ between species in the way they do. For example, males in most mammals appear entirely specialised on mating with many females, whereas males in many birds also invest in offspring quality by providing paternal care. Alternatively or additionally, males may invest in enhancing their paternity share in any mating they get. Taken to the extreme, this may result in males investing maximally in gaining paternity with one or two females only, in the absence of paternal care. Mating systems with monogynous (or bigynous) males and polyandrous females are taxonomically widespread but relatively rare overall. In spiders, however, low male mating frequencies have evolved several times independently and are associated with remarkable adaptations that include sexual cannibalism and genital damage. In the first part of this chapter, we describe the mating strategies, and the associated costs and benefits of sexual cannibalism and genital damage, of selected spider species that represent independent evolutionary origins of these traits. We then introduce models that investigate the evolution of mating systems with low male mating frequencies. The models predict that a male-biased sex ratio is required for monogyny to evolve. We outline how such a sex ratio bias may have arisen in concert with female-biased sexual size dimorphism. Finally, we discuss monogyny in the light of sexual conflict theory.