Data from: Benefits of polyandry: molecular evidence from field-caught dung beetles

When females mate with multiple males, they set the stage for post-copulatory sexual selection via sperm competition and/or cryptic female choice. Surprisingly little is known about the rates of multiple mating by females in the wild, despite the importance of this information in understanding the potential for post-copulatory sexual selection to drive the evolution of reproductive behavior, morphology, and physiology. Dung beetles in the genus <i>Onthophagus</i> have become a laboratory model for studying pre- and post-copulatory sexual selection, yet we still lack information about the reproductive behavior of female dung beetles in natural populations. Here, we develop microsatellite markers for <i>Onthophagus taurus</i>, and use them to genotype the offspring of wild-caught females, and to estimate natural rates of multiple mating and patterns of sperm utilization. We found that <i>O. taurus</i> females are highly polyandrous: 88% of females produced clutches sired by at least two males, and 5% produced clutches with as many as five sires. Several females (23%) produced clutches with significant paternity skew, indicating the potential for strong post-copulatory sexual selection in natural populations. There were also strong positive correlations between the number of offspring produced and both number of fathers and paternity skew, which suggests that females benefit from mating polyandrously by inciting post-copulatory mechanisms that bias paternity towards males that can sire more viable offspring. This study evaluates the fitness consequences of polyandry for an insect in the wild, and provides strong evidence that female dung beetles benefit from multiple mating under natural conditions.