Evolution Of Sexual Cannibalism Research Articles

Mutual wing‐eating between female and male within mating pairs in wood‐feeding cockroach

AbstractThe behavior of eating their mates or a part of their mate's body has been studied in sexual cannibalism or nuptial feeding. In these behaviors, only one sex eats the other unilaterally. Within mating pairs of a wood‐feeding cockroach (Salganea taiwanensis), males and females eat the mate's wings each other, which is the first “mutual” case in these behaviors. Because the evolution of sexual cannibalism and nuptial feeding has been explained based on unilaterality, this mutual eating should have a new significance of reproduction. We described this behavior quantitatively and suggest a new hypothesis based on true monogamy, the mating system of S. taiwanensis, copulating with only one mate throughout life. Under true monogamy, the fitness of the mate is the same as own fitness and the pairs are free from sexual conflict. If the wing eating increases the ability of the mate to raise the offspring, this behavior is adaptive for the eater as well as its mate.

Sexual Cannibalism: High Incidence in a Natural Population with Benefits to Females

BackgroundSexual cannibalism may be a form of extreme sexual conflict in which females benefit more from feeding on males than mating with them, and males avoid aggressive, cannibalistic females in order to increase net fitness. A thorough understanding of the adaptive significance of sexual cannibalism is hindered by our ignorance of its prevalence in nature. Furthermore, there are serious doubts about the food value of males, probably because most studies that attempt to document benefits of sexual cannibalism to the female have been conducted in the laboratory with non-natural alternative prey. Thus, to understand more fully the ecology and evolution of sexual cannibalism, field experiments are needed to document the prevalence of sexual cannibalism and its benefits to females.Methodology/Principal FindingsWe conducted field experiments with the Mediterranean tarantula (Lycosa tarantula), a burrowing wolf spider, to address these issues. At natural rates of encounter with males, approximately a third of L. tarantula females cannibalized the male. The rate of sexual cannibalism increased with male availability, and females were more likely to kill and consume an approaching male if they had previously mated with another male. We show that females benefit from feeding on a male by breeding earlier, producing 30% more offspring per egg sac, and producing progeny of higher body condition. Offspring of sexually cannibalistic females dispersed earlier and were larger later in the season than spiderlings of non-cannibalistic females.Conclusions/SignificanceIn nature a substantial fraction of female L. tarantula kill and consume approaching males instead of mating with them. This behaviour is more likely to occur if the female has mated previously. Cannibalistic females have higher rates of reproduction, and produce higher-quality offspring, than non-cannibalistic females. Our findings further suggest that female L. tarantula are nutrient-limited in nature and that males are high-quality prey. The results of these field experiments support the hypothesis that sexual cannibalism is adaptive to females.

Sexual size dimorphism mediates the occurrence of state-dependent sexual cannibalism in a wolf spider

Most research on sexual cannibalism has focused on factors influencing female motivation to engage in cannibalism. However, a critical factor that may mediate the actual occurrence of sexual cannibalism is male vulnerability to female attacks. We tested whether sexual size dimorphism (SSD) affected whether hungry females were successful in sexual cannibalism in a moderately size dimorphic wolf spider, Hogna helluo. Experimentally food-limited females cannibalized males more frequently than did well-fed females. However, in a correlational study, female body condition was only a significant predictor of the occurrence of sexual cannibalism if SSD was included in the model. Our results suggest that SSD is an important factor mediating the occurrence of sexual cannibalism in H. helluo by affecting male vulnerability to female attacks. Consideration of factors affecting male vulnerability to cannibalistic attacks by females may be critical to understanding the occurrence and evolution of sexual cannibalism.

Fitness consequences of sexual cannibalism in female Argiope bruennichi

The evolution of sexual cannibalism as the most extreme form of nuptial feeding is still poorly understood. Although increasing evidence suggests that female aggressiveness is related to other aspects of foraging behaviour, it is not clear whether the nutritional value of a male is sufficient to provide an adaptive significance for sexual cannibalism. A widely cited though rarely tested explanation is based on a paternal investment model, and predicts that consumption of a male results in increased female fecundity. The available evidence is either correlational or restricted to species with relatively large and potentially nutritious males, and different studies have come to different conclusions. Here we present a test of the paternal investment hypothesis using the very cannibalistic and highly size-dimorphic spider Argiope bruennichi. After a preset schedule, we had females consume none, one or two males independent of the female's cannibalistic behaviour. Consumption of male bodies did not result in any detectable fitness benefit for the female: neither the number of clutches, nor clutch size or hatching success were affected by consumption of males. The frequency of cannibalism was around 80%, independent of the female mating status. We did not observe male complicity, but cannibalism was associated with prolonged copulation. This suggests a sexually selected benefit of cannibalism for males. We conclude that the paternal investment hypothesis does not explain the existence of sexual cannibalism in A. bruennichi and probably not in other spider species with a pronounced sexual size dimorphism.

Sexual cannibalism in Nephila plumipes as a consequence of female life history strategies

Abstract The evolution of sexual cannibalism has been modelled as both an adaptive and nonadaptive female strategy. Recent evidence from several species suggests a connection between female foraging and sexual cannibalism, but the precise benefits for females have remained obscure. Here, we investigate the difference between cannibalistic and noncannibalistic female Nephila plumipes by removing the potential nutritional benefit of cannibalism. Courting and mating males that were killed by a female were immediately removed so that the female could not consume them. Nevertheless, cannibalistic females gained more mass from maturation to oviposition and produced larger first clutches than noncannibalistic females, although cannibalistic females matured at a smaller size and mass than noncannibalistic females. In juvenile instars, mass gain was generally smaller in females that moulted in a good condition but intermoult intervals were shorter. However, the time from maturity to oviposition was not shorter in females that matured in a good condition. Male behaviour did not differ according to the risk of cannibalism. We suggest that sexual cannibalism in N. plumipes is a side-effect of an increased foraging vigour of females that matured at a smaller size and body mass. Selection pressure on males to avoid cannibalism may be weak because of limited mating opportunities.