Fitness effects of nuptial gifts in the spiderPisaura mirabilis: examination under an alternative feeding regime

Abstract

Nuptial feeding has variable effects on fitness within a species, partly driven by variation in female diet. We investigate nuptial feeding in the spider Pisaura mirabilis (Clerck, 1757) under a feeding regime that has not been explored: starvation after mating and gift consumption. We vary gift size and gift number to examine the effects on mating behavior and components of female fitness. With regard to gift size, copulation duration increased with larger gift size, but no component of female fitness was affected (time to oviposition, egg sac mass, female lifespan). These results corroborate other examinations of gift size in P. mirabilis. Given a likely male benefit (prolonged copulation) for larger gift size and no demonstrated female benefit, sexual conflict stands as a likely explanation for male benefits due to large nuptial gift size. With regard to gift number, components of female fitness were not affected by the consumption of one or two extra gifts. This agrees with other studies, although we note that some experiments have found the consumption of extra gifts to increase female fitness. As for males, they were more likely to copulate when they had gifts, as in other studies. We conclude some support for sexual congruence with regard to gift number, as males and females stand to benefit simultaneously from the mere presence of the gift, and females might benefit from the consumption of multiple gifts. Thus, both sexual conflict and sexual congruence appear to be at work regarding the evolution of nuptial gifts in Pisaura mirabilis.