The genetic mating system of the two-spotted goby during sex-role reversal

An outstanding question in behavioral ecology is how the strength of sexual selection affects the evolution of alternative reproductive tactics. In this study, we investigated the genetic mating system of the two-spotted goby (Gobiusculus flavescens), a species that has dynamic sex-roles. We developed four polymorphic microsatellite markers and used them to conduct parentage analyses on 21 nests collected during the latter portion of the breeding season when sex roles are reversed. Results of this study indicate that male G. flavescens mate with multiple females and enjoy confidence of paternity. We detected only one instance of sneaking, so cuckoldry contributed a very small percentage (~0.1%) of the total fertilizations in this population. Nests were nearly full and males that maintain larger nests have higher mating and reproductive success, irrespective of body size. Overall, our investigation shows a considerably lower prevalence of male alternative reproductive tactics in G. flavescens compared to related species in the Pomatoschistus clade. We believe that the unique sex role reversal during the time of collection may account for the absence of sneaking encountered in this species. However, the exact ecological factors responsible for the evolution of male alternative reproductive tactics in G. flavescens require further investigation in this and closely related species.