Complex effects of sex reversal on reproductive success in wild frogs

Sex reversal, when the environment overrides genotypic sex determination, may hasten or delay climate-driven extinction in ectothermic animals, depending on sex-reversed individuals' reproductive ability and offspring viability. Empirically, next to nothing is known about these traits in natural populations. Here, we present a comprehensive dataset of wild frogs to compare sex-reversed and sex-concordant males for fertility, attractiveness to females, intrasexual competitiveness, and offspring survival in various environments. We demonstrate uncompromised potential of sex-reversed males to mate and produce viable offspring, which are all genotypic females but have increased sex-reversal propensity. However, sex-reversed males realize reduced paternity in natural populations, possibly due to cryptic female choice. Furthermore, offspring of sex-reversed sires exhibit increased vulnerability to viral infection after heat stress. Our theoretical model predicts that these handicaps of sex-reversed males compromise their ability to compensate by producing female offspring for climate-driven male bias in phenotypic sex ratios, which reduces population viability. Therefore, sex reversal exacerbates the biodiversity consequences of environmental change.