Teneral matings in fruit flies: male coercion and female response

Extensive research indicates that sexually mature female fruit flies typically choose with whom to mate, a process that is crucial for the operation of sexual selection and population divergence via female choice. We followed up on field data suggesting that male fruit flies (Drosophila melanogaster) force copulate with teneral females, which are recently eclosed females characterized by their folded wings and soft, light coloured bodies. Our results indicated that males succeeded in mating with about 20% of the teneral females from our Canton-S population and 15% of the teneral females from a local, wild-caught D. melanogaster population. Males were most likely to mate with recently eclosed females and failed to mate with females older than 1 h posteclosion. Close behavioural observations indicated coercion by the males and resistance by the teneral females. The teneral females continued to fight off males throughout copulation and this probably contributed to the shorter mating duration of teneral females relative to that of mature females. Although teneral females failed to foil some forced copulation attempts, they could reduce the impact of such copulations by subsequently remating with a male of their choosing. Indeed, tenerally mated females were six times more likely to remate than were control females that had mated when mature. Our results substantiate a novel aspect of sexual conflict in fruit flies, which could counteract processes driven by female mate choice.