The role of species-specific sensory cues in male responses to mating rivals in D. melanogaster fruitflies

Complex sets of cues can be important in recognising and responding to conspecific mating competitors and avoiding potentially costly heterospecific competitive interactions. Within Drosophila. melanogaster, males can detect sensory inputs from conspecifics to assess the level of competition. They respond to rivals by significantly extending mating duration and gain significant fitness benefits from doing so. Here, we tested the idea that the multiple sensory cues used by D. melanogaster males to detect conspecifics also function to minimise ‘off-target’ responses to heterospecific males that they might encounter (D. simulans, D. yakuba. D. pseudoobscura or D. virilis). Focal D. melanogaster males exposed to D. simulans or D. pseudoobscura subsequently increased mating duration, but to a lesser extent than following exposure to conspecific rivals. The magnitude of rivals responses expressed by D. melanogaster males did not align with genetic distance between species and none of the sensory manipulations caused D. melanogaster to respond to males of all other species tested. However, when we removed or provided ‘false’ sensory cues, D. melanogaster males became more likely to show increased mating duration responses to heterospecific males. We suggest that benefits of avoiding inaccurate assessment of the competitive environment may shape the evolution of recognition cues.