Longevity cost of reproduction for males but no longevity cost of mating or courtship for females in the male-dimorphic dung beetle Onthophagus binodis

Abstract

Life history theory predicts a trade-off between current and future reproduction. Despite a wealth of research on the cost of reproduction for females, there have been very few studies that have looked at the cost of reproduction for males. Longevity is closely related to the opportunity for future reproduction, and thus decreased longevity in response to current reproductive effort has been used as a measure of the cost of reproduction. Here we examine the cost of reproduction for males and females in the dung beetle Onthophagus binodis. Like many onthophagines, O. binodis exhibit dimorphic male morphology; major males develop a large pronotal horn while minor males remain hornless. Alternative morphologies are associated with alternative reproductive tactics. Thus, we ask whether major and minor males pay different costs of reproduction. We found that in contrast to previous work on Diptera, mating is not costly in terms of reduced longevity for female dung beetles. Despite a longevity cost of reproduction for males, we found no evidence for differential longevity costs associated with alternative reproductive tactics.