Stepping off the pasture: Evidence of widespread alternative male mating tactics in the yellow dung fly

Geoff Parker's investigations of the yellow dung fly mating system revitalized interest in sexual selection theory, sparked development of sperm competition and sexual conflict theories, and stimulated use of this species as an important model system. Numerous studies across widespread populations have demonstrated large-male advantages in competition contests occurring on dung in cow pastures; however, recent work suggests that smaller males adopt an alternative mating tactic by avoiding dung and instead copulating with females at foraging sites. Though this finding has the potential to expand our understanding of sexual selection in yellow dung flies, such behavior has to date been documented at only one field site, raising the possibility that this phenomenon is highly localized. Here, we report the expression of size-dependent alternative mating tactics across three discrete populations. These findings provide a cautionary tale for researchers limiting their attention to aggregation sites where study organisms are most conveniently encountered.