Fine-scale genetic pattern and evidence for sex-biased dispersal in the tungara frog, Physalaemus pustulosus

Tungara frogs (Physalaemus pustulosus) are a model system for sexual selection and communication. Population dynamics and gene flow are of major interest in this species because they influence speciation processes and microevolution, and could consequently provide a deeper understanding of the evolutionary processes involved in mate recognition. Although earlier studies have documented genetic variation across the species' range, attempts to investigate dispersal on a local level have been limited to mark-recapture studies. These behavioural studies indicated high mobility at a scale of several hundred metres. In this study we used seven highly polymorphic microsatellite loci to investigate fine-scaled genetic variation in the tungara frog. We analysed the influence of geographical distance on observed genetic patterns, examined the influence of a river on gene flow, and tested for sex-biased dispersal. Data for 668 individuals from 17 populations ranging in distance from 0.26 to 11.8 km revealed significant levels of genetic differentiation among populations. Genetic differentiation was significantly correlated with geographic distance. A river acted as an efficient barrier to gene flow. Several tests of sex-biased dispersal were conducted. Most of them showed no difference between the sexes, but variance of Assignment Indices exhibited a statistically significant male bias in dispersal.