Spotting the top male: sexual selection in a lek-mating paper wasp, Polistes dominulus.

摘要

Acquiring mates is a problem ubiquitous in the animal kingdom. Males typically face the brunt of the burden by bearing the elaborate weaponry and ornamentation required to compete for and attract females. Despite prolific interest in understanding the dynamics of male-male competition and female choice, many questions remain. In particular, there is little understanding of how sexual selection operates in systems lacking obviously costly ornamentation, or what drives female choice in systems in which males provide no tangible resources. Polistes paper wasps serve as a uniquely-suited model organism with which to address these questions: they epitomize intense competition as they have lek-based mating systems; females are genetically monogamous, suggesting strong female choosiness; and females hibernate between mating and producing offspring, making male ejaculate quality an important factor for female fitness. Finally, male paper wasps are unique among lekking organisms in that they do not appear to possess the obviously costly ornamentation typical of lekking males. Despite these interesting facets of paper wasp reproductive biology, it remains poorly studied. Here, I examine multiple aspects of the mating system of Polistes dominulus paper wasps, with the following objectives: (1) to identify sexually selected signals, (2) to determine whether identified signals advertise quality information, and (3) to determine how females benefit from choice in a lekking system. I show that while chemical information is unrelated to reproductive success, male morphology functions as condition dependent sexually selected quality signals: males use dorsal abdominal spots in both inter- and intra-sexual competition, and larval diet influences the development of these spots. Further, female choice for attractive spots results in direct benefits to females, with females whose mates advertise high quality surviving hibernation longer than females whose mates advertise low quality. Overall, these results demonstrate that male ornaments are important mediators of mating dynamics in Polistes dominulus. Moreover, they show that females can gain direct benefits in non-economic mating systems, providing an alternative hypothesis to "good genes" models of female choice on leks. This work builds a foundation necessary for paper wasps to become model organisms for studying sexual selection and lekking dynamics.