Sexual conflict may occur when males and females have conflicting optimal fitness strategies with regard to reproduction, such as when males favour greater mating rates than females. Sexual conflict may lead to antagonistic co-evolution between the sexes, with one sex evolving a trait favouring its reproductive interests and the opposite sex subsequently evolving countermeasures, potentially leading to an evolutionary arms race between males and females. Co-evolution generated by sexual conflict has been championed as a major mechanism of evolution, but the importance and scope of this process remains controversial.
Our research on sexual cannibalism represents a significant body of work offering important and genuinely novel insights into our understanding of sexual conflict. First, precopulatory sexual cannibalism represents an especially extreme conflict of interest in polygynous systems, with males that succumb to female attack having a complete loss of future – and often current – reproduction. More commonly studied costs, such as unwanted matings or injury during copulation, pale in comparison to the costs of precopulatory cannibalism for male mantids. Also, cannibalism is significantly more costly for male mantids than cannibalism for most male spiders, where male consumption occurs during copulation (as opposed to before in mantids) and males are only able to mate twice in their lifetime (as opposed to multiple times in mantids). Second, sexual cannibalism presents an unusual case in which females attempt to impose their reproductive interests on males, and males are thus predicted to evolve countermeasures. This situation contrasts with the vast majority of sexual conflict studies in which males attempt to manipulate female reproductive behaviour to their advantage. The generality of sexual conflict theory depends on its applicability to such uncommon cases, making our research extremely important.