Abstract
Complex sets of cues can be important in recognizing 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 minimize “off‐target” responses to heterospecific males that they might encounter (Drosophila simulans, Drosophila yakuba, Drosophila pseudoobscura, or Drosophila 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.
Highlights
The ability of individuals to discriminate between conspecifics and heterospecifics is key to maximizing reproductive success and avoiding potentially costly heterospecific interactions (Coyne & Orr, 2004)
−0.2 0.5 0 were increased after exposure to D. simulans and D. pseudoobscura (Table 2). These findings suggest that the addition of D. melanogaster olfactory cues through cuticular hydrocarbons (CHCs) extracts either rendered males more likely to respond to heterospecifics (D. simulans and D. pseudoobscura) or had no effect
The results show that in the absence of manipulations to sensory cues, exposure of D. melanogaster males to heterospecifics could elicit significant increases in mating duration, but not to the extent observed following exposure to conspecific rival males
Summary
The ability of individuals to discriminate between conspecifics and heterospecifics is key to maximizing reproductive success and avoiding potentially costly heterospecific interactions (Coyne & Orr, 2004). There are many examples in which males increase reproductive investment in ejaculate composition, or in behaviors such as mate guarding and copulation duration, if they perceive a high likelihood of sperm competition (Bretman, Gage, & Chapman, 2011; Wedell, Gage, & Parker, 2002). We tested whether D. melanogaster males responded to males of four other species when exposed to a full sensory repertoire from the heterospecifics or when single sensory cues were removed in turn (Bretman, Westmancoat et al, 2011) This enabled us to test two predictions: (1) Given a full sensory repertoire, males should avoid investing in “rivals’ responses” to heterospecifics that pose no sperm competition threat and (2) the sensory modalities used to convey species-specific information can be identified by manipulating cues in order to “trick” males into responding to heterospecific rivals as they would to conspecifics
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