Repeated copulations as a strategy to maximize fertilization in the fly, Dryomyza anilis (Dryomyzidae)

Abstract

In the fly, Dryomyza anilis, males copulate repeatedly with the same female during oviposition. Each copulation bout consists of intromission followed by several tapping sequences during which the male touches the external genitalia of the female with his claspers. The relative fertilization success of the last male to mate with the female increases with the number of tapping sequences. In this study, male benefits of repeated copulation bouts were examined by comparing matings with the same number of tapping sequences in one and several copulation bouts. The relative fertilization success for the last male increased with successive copulation bouts. Simulated oviposition patterns showed that fertilization success in matings with many copulation bouts was higher than in matings with one bout only if eggs were distributed between bouts in a certain way. These predicted oviposition patterns were compared with natural ones. Although males may benefit from repeated copulation, females are likely to prefer matings with quick oviposition. This intersexual conflict may also affect natural oviposition patterns. It is suggested that repeated copulation in D. anilis may have evolved in connection with males trying to secure their paternity because females can discharge sperm at any moment during mating.