JessiCA
KENDALL-BAR
ART & SCIENCE

              The spatial distribution of organisms can provide insight into their mating systems, either revealing mating preferences (intersexual selection for ornaments), competition for mates (intrasexual selection for armaments), or both. Teasing apart the relative contributions of these selective forces is a critical step in understanding mating systems, particularly given the potential combinations and complexities that arise when both sexes possess weaponry. 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 sometimes substantially larger, than females) and weaponry (males possess asymmetrical, curved forceps, whereas females have straight forceps). We varied sex, body size, and forceps asymmetry among trios of earwigs and examined their spatial distribution under conditions where movement was restricted to promote either intersexual choice or intrasexual competition. Our results indicate strong sexual selection for larger sizes through both competition and choice in both sexes. However, females had no preference for males based on forceps asymmetry. We discuss how the competition and cohabitation patterns provide insight into the mating system, including how the possession of weaponry by both sexes could operate in intrasexual competitive battles as well as serve as a basis for assessing the quality of a potential mate.