MALE ASYMMETRY AND POSTCOPULATORY SEXUAL SELECTION IN THE FLY DRYOMYZA-ANILIS

The significance of male asymmetry in postcopulatory sexual selection was studied in the fly Dryomyza anilis by examining whether male asymm etry is related to fertilization success. The traits measured were win g length, tibia length and the length of small and large claspers. The male claspers are situated at the tip of the abdomen, functional pair of claspers consists of a large and a small clasper on the same side of the body. These claspers are used to tap the female abdomen after s perm transfer, which has been shown to increase fertilization success for the mating male. Fertilization success was negatively related to t he fluctuating asymmetry of wing length, suggesting either female pref erence for more symmetrical males or a relationship between male asymm etry and intrasexual selection which was reflected in mating performan ce. Fertilization success was also related to the length of small clas pers, decreasing with increasing length of the claspers. In addition, males with asymmetrical small claspers enjoyed higher fertilization su ccess than symmetrical ones. This study shows that fluctuating asymmet ry in wing length is an important fitness trait in postcopulatory sexu al selection. Since male tapping affects sperm distribution in the fem ale's sperm storage organs, the higher fertilization success of males with asymmetrical small claspers could have a functional relationship with the asymmetrical position of female sperm storage organs.