No association between sexual size dimorphism and life histories in spiders

Abstract

In spiders, females are commonly larger than males. The majority of hypotheses that attempt to explain sexual size dimorphism in spiders concentrate on reduction in male size, although there is evidence to suggest that the independent evolution of marked sexual size dimorphism and reversion to a less extreme dimorphic state has occurred several times. Recent debate has centred on two conflicting hypotheses involving male dwarfism and increased female size through fecundity selection, and has focused on the golden orb-weaving spider, Nephila clavipes (Tetragnathidae), and its relatives. In Nephila, males are tiny in comparison to females, however, other orb-web spiders do not show such extremes in dimorphism. Here, we incorporate phylogeny into a comparative investigation of the patterns of sexual dimorphism predicted by the hypothesis of male dwarfism via sex-linked differential mortality during mate searching and note an absence of supporting evidence. There was no evidence of the predicted association between male and female size and sexual size dimorphism with life histories, exemplified by variation in predatory strategies, in spiders.