Meeting Abstract
Sexual selection often leads to exaggerated traits that provide reproductive advantages either through mate choice (intersexual selection for ornaments) or competition (intrasexual selection for armaments). Teasing apart the relative contributions of these selective forces is a critical step in understanding mating systems. In cases where both sexes possess weaponry, many potential combinations and complexities arise. We examined the mating system of the maritime earwig Anisolabis maritima, an insect well-suited for studies of sexual selection because males differ markedly from females in body size (males are more variable in size, and often substantially larger, than females) and weaponry (males possess asymmetrical, curved forceps whereas females have straight forceps). We examined the roles of these two factors, body size and forceps asymmetry, as it relates to four types of sexual selection: female choice, male choice, male competition, and female competition. Using trios of earwigs in artificial arenas where we could restrict the movement of certain individuals, we monitored the distribution of free-moving individuals to determine the relative roles that these factors may play in spatial patterns and gain insight into the mating system. Our results revealed strong sexual selection for larger sizes through both competition and choice, but there was no preference based on forceps asymmetry. We found significant results in all four trial types, including not only the more traditional male competition and female choice, but also female competition and male choice. This pattern suggests that the weaponry possessed by both sexes could operate in intrasexual competitive battles as well as serve as a basis for assessing quality of a potential mate.
