Condition dependence varies with mating success in male Drosophila bunnanda

Although key to sexual selection theories, condition dependence has proven a challenging area of empirical research. It is expected that availability of resources will affect both mean and variation of sexual trait expression, with lower mean and greater variation in harsher environments. Here, I manipulated the environment in a laboratory population of Drosophila bunnanda to test for condition dependence of sexually selected traits. Sexually successful and unsuccessful males differed in how the environment affected sexual trait expression. Specifically, sexual trait attractiveness declined more rapidly with declining resources in sexually unsuccessful males, consistent with the expectation that low quality males were less able to meet the greater signalling costs associated with harsher environments. This study illustrates the potential insights into condition dependence that might be gained through considering sexual trait expression and mating success within the same manipulative experimental design.