Factors Influencing Sexual Cannibalism And Its Effects On Fecundity And Offspring Survival In The Wolf Spider Pardosa Pseudoannulata (Araneae:Lycosidae)

Sexual cannibalism, an extreme form of sexual conflict, is defined as the killing and consumption of an actual or potential mate by a female before, during, or after copulation. Sexual cannibalism has been observed in at least30species of terrestrial arthropods, including members of all orders of arachnids and three orders of insects. It is hypothesized to have evolved as a way to obtain a high-quality meal, extreme mate choice or as a consequence of female aggressive spillover.In the present study, we examined the factors likely to affect sexual cannibalism in wolf spider Pardosa pseudoannulata (Bosenberg&Strand,1906), including female and male mating status, female egg-laid status, female hunger level, female adult age and mate size dimorphism. We also tested effects of sexual cannibalism on the fecundity and offspring survival of cannibalistic females. The results showed:1.10%of P. pseudoannulata virgin females cannibalized the approaching males before mating and28%of P. pseudoannulata virgin females immediately cannibalized the males after mating. The rate of post-mating sexual cannibalism was significantly higher than that of pre-mating sexual cannibalism (p=0.007). None (0/32) of the previously mated females succeeded in mating with virgin males, and previously mated females tended to engage in significantly higher rates of attacks compared to virgin females (p=0.004), but no difference was found in pre-mating sexual cannibalism between previously mated females and virgin females (p=0.708). None (0/33) of the female that had laid egg sacs succeeded in mating with virgin males, female that had laid egg sacs tended to engage in a significantly higher rate of attacks (p=0.001) and sexual cannibalism (p<0.001) compared to virgin females before mating. Regardless of pre-mating or post-mating, females in the small chamber tended to engage in a significantly higher rate of sexual cannibalism (pre-mating: p<0.001, post-mating:p=0.002) compared to larger chamber.2. We did not find any significant effect of sexual cannibalism on fecundity in female’s first egg sacs. Cannibalistic females did not have a shorter pre-oviposition period (p=0.144). Females did not benefit from consuming a single male by producing significantly more offspring per egg sac (Cannibalistic females, mean±SEM offspring=84±11.77; non-cannibalistic females, mean±SEM offspring=66±6.90)(p=0.313).48.15%(52/108) of the spiderlings produced by cannibalistic females could survive longer than30days. In contrast, only11.88%(19/160) of the spiderlings produced by non-cannibalistic females could survive30days. The survival of the spiderlings produced by cannibalistic females was significantly higher than that of the spiderlings produced by non-cannibalistic females(p<0.001). Our findings do not support the hypothesis that sexual cannibalism evolves as an adaptive component of female foraging strategy, and it benefits offspring survival from paternal investment.