The costs of harassment in the adzuki bean beetle

Abstract

Male harassment of females can be one form of premating sexual conflict, which can impose fitness cost on females. We measured the cost of male harassment on female fitness in the adzuki bean beetle, Callosobruchus chinensis, by using impotent males whose aedeaguses were ablated. These males harassed females but could not copulate with them. We measured the fitness of the females that received neither harassment nor additional copulations (cl females) and those that cohabited with ablated males (can harass but cannot copulate) (ab females). The fitness of the ab females was 18.6% lower than that of the cl females, indicating that the females incur a large fitness cost of the male harassment. Additionally, to examine whether females can avoid the fitness cost of harassment by accepting copulation (convenience polyandry), we compared the rate at which the females were harassed and the fitness of the females that cohabited with normal males (can harass and copulate) (nl females) with those of the ab females. The harassment rate and fitness of the nl females did not differ significantly from those of the ab females. These results did not positively support the convenience polyandry hypothesis.