No evidence of negative frequency-dependent selection in alternative reproductive tactics in a bulb mite

Abstract

Alternative reproductive tactics typically involve males aggressively competing for access to females coexisting with males using nonaggressive, often sneaky tactics. When tactics are heritable, game-theoretic models are commonly invoked to explain such coexistence. These models, including the classic Hawk and Dove model, assume that a tactic's success decreases with its frequency in a population; however, evidence supporting this assumption is scarce. In this study, we investigated the frequency dependence of male reproductive success in an acarid mite, Rhizoglyphus robini, where heritable male morphs exhibiting alternative reproductive tactics, aggressive fighters and benign scramblers, coexist. We placed focal fighter or scrambler males in populations dominated by scramblers or fighters or containing even proportions of both morphs and, using the sterile male technique, determined the number of progeny they sired and the number of females inseminated. Although we found that focal male reproductive success differed depending on mating tactics between competitive mating environments, these differences do not support our predictions and the role of negative frequency-dependent selection in this system. These results question the Hawk–Dove model as an explanation and indicate other mechanisms are required to explain the coexistence of alternative reproductive tactics in R. robini.