Sexual and nonsexual cannibalism have different effects on offspring performance in redback spiders

Sexual cannibalism is often set apart from other forms of cannibalism; however, no studies have directly compared the fitness consequences of these 2 types of cannibalism. Here, we compared the consequences of cannibalism of a male by a female outside the context of mating (referred to as nonsexual cannibalism) and within the context of mating (referred to as sexual cannibalism) for the propensity to remate, fecundity, and offspring traits of female redback spiders Latrodectus hasselti. Although the timing of cannibalism relative to copulation is critical for male fitness, it is still unclear whether it can also influence female fitness, beyond the fertilization of eggs. Our results showed that sexual cannibalism and nonsexual cannibalism had different effects on offspring survival and growth. Sexually cannibalistic females produced offspring that survived better and grew faster than nonsexually cannibalistic or noncannibalistic females. By experimentally manipulating the quality of prey given to offspring, we showed that these effects were dependent on the spiderlings’ diet quality. In particular, the effects of sexual cannibalism on offspring growth and survival were clearer when offspring were, respectively, fed a high-nutrient diet and a low-nutrient diet. However, sexual cannibalism did not increase offspring tolerance to starvation. Additionally, we did not find any effect of nonsexual cannibalism nor sexual cannibalism on female fecundity or subsequent sexual receptivity. As copulation duration did not account for these effects on offspring performance, our findings suggest that copulation occurring simultaneously with cannibalism plays an essential role in the fitness consequences of this behavior.