PFENNIG, K.S.*; TINSLEY, R.C.: Parasites, female mating behavior and sexual selection on male traits

Female choice for parasite-free mates often may favor the evolution of elaborate male traits that indicate male health. Yet, parasite infection of females can alter their mate preferences, thereby mitigating selection on male traits. Here, we show that female spadefoot toads face a paradox. Whereas males that can provide females with enhanced fertilization success are more likely to harbor sexually-transmittable parasites, unparasitized males may be less able to fertilize an entire female’s clutch. We found that female mate preferences depended on the female’s own infection status. In particular, unparasitized females preferred mates that potentially provide greater fertilization success despite the risk that females accrue of selecting parasitized mates. By contrast, parasitized females avoided parasitized mates, even though such males may provide enhanced fertilization success. Consequently, the different preferences between parasitized and unparasitized females reduce directional selection for exaggerated male traits. Our results suggest that to understand the effects of parasites on the evolution of mate choice behavior, it is necessary to evaluate how female mate selection is altered when females themselves are infected.