Intersexual Conflict in Spiders

Abstract

Reproductive strategies of males and females usually differ and, as a consequence, may impose asymmetric costs of reproduction on the two sexes and result in conflict between the sexes. In spiders, males do not provide parental care and females can store sufficient sperm for several clutches. These characteristics define the stage for a conflict between males and females that occurs mainly over the frequency of mating. Factors such as sexual size dimorphism, operational sex ratio, mating system and life-history strategies are likely to influence the degree of conflict and its outcome for different species. Male spiders may suffer large costs of mating due to mate search, assessment of female condition, courtship and cannibalistic tendencies of their mates. Courtship may reduce cannibalism, although in some cases, males benefit from being cannibalised by having an increased fertilisation rate or greater offspring fitness. In some species, limited mating capacities will increase the value of the current mating relative to future reproduction. Apart from a possible benefit of genetic variability within a clutch, females may not benefit from multiple mating and multiple mating may even be costly. Exceptions occur if additional resources are provided by males or when offspring fitness increases with additional mating. Forced copulation, prey theft, loss of the web and reduction of foraging time can all result in reduced reproductive success for females. We discuss the interacting influences of life-history traits (especially patterns of growth and maturation and sexual size dimorphism) and the reproductive strategies of males and females, using a semelparous spider, Stegodyphus lineatus (Eresidae), as an example of a species in which males and females can have strongly conflicting interests.