Two matings lead to more copulatory wounding than a single mating in female Drosophila melanogaster

Copulation can result in males inflicting wounds to the female genitalia, so-called traumatic mating. Such wounds are potentially costly as they could be entry points for infections, and they have been associated with a shorter lifespan in an insect species. In many species of insects, females mate with more than one male, which leads to the question of whether the number of matings affects the amount of genital damage that females suffer from those matings. Here we test whether copulation frequency affects the number or size of genital wounds in Drosophila melanogaster. Females who mated twice had more genital wounds and a larger total area of wounding, compared to females who mated once. However, females who refused to mate a second time had a similar area of wounding as females who mated twice. We found that wounds to the ventral abdomen also increased with increased mating frequency. Our results support the idea that polyandry can incur an under-appreciated cost in terms of increased female copulatory wounding. Investigating genital and abdominal wounds is crucial to a better understanding of the consequences of sexual conflict and the selective pressures shaping mating behaviour.