Selection on male physical performance during male-male competition and female choice

Male contest competition and female choice are key features of the mating systems of many species, and whole-organism performance may be targeted by both mechanisms given the dynamic body movements required during fighting and courtship displays. Using the dimorphic horned dung beetle Onthophagus taurus as a model system, we tested whether physical performance was important in determining a male's victory in fights, and whether successful fighters were preferred by females as mates. We found that physical strength, horn length, and body mass were significant predictors of male fighting success, but males that won fights were not more attractive to females. Rather, females preferred males that delivered a high courtship rate, which was not correlated with strength, horn length, or body mass, but previously has been shown to be genetically correlated with body condition. The fact that there was no relationship between fighting success and mating success suggests that selection on traits favored by male-male competition and female choice can act relatively independently in this species, although both mechanisms appear to favor traits (strength and courtship, respectively) that are linked to a male's ability to acquire and allocate resources for mass gain. Future work is needed to determine the relative contributions of these processes to the total strength of sexual selection acting on male phenotypes.