Mate copying in Drosophila melanogaster males

Abstract

To assess potential mates' quality individuals can observe sexually interacting conspecifics. Such social information use is called mate copying and occurs when observer individuals witnessing sexual interactions of conspecifics later show a mating preference for mates that were seen mating. Most studies have focused on female mate copying, as females are usually the choosy sex. However, much less is known about the existence of male mate copying, probably because of the usual strong asymmetry in sex roles. Mate copying has been documented in female Drosophila melanogaster, and here we report on experimental evidence for mate copying in males of this species in which females can actively reject males and prevent copulation. As mate choice implies high costs for males we assumed that they perform mate copying as well. We created two artificial female phenotypes by randomly dusting females with green or pink powders, and virgin naive observer males were given the opportunity to see a demonstrator male choosing between a pink and a green demonstrator female. Immediately afterwards, observer males were given the choice between two new females, one of each colour. To circumvent the difficulty of determining actual male mate preference, we used two complementary indices of male mate choice, both of which provided evidence for male mate copying. Informed observer males showed a bias towards females of the colour they saw being chosen during demonstrations, while uninformed males chose randomly between pink and green females. This suggests that male fruit flies can also perform mate copying. Although significant, our results in males were less clear-cut than in females in previous studies. However, like females, D. melanogaster males can mate copy based on a single observation. The importance and generality of such mate copying abilities in nature, and their potential impact on the evolution of Drosophila and probably other invertebrates, need further exploration.