Epigenomic changes in the túngara frog (Physalaemus pustulosus): possible effects of introduced fungal pathogen and urbanization

Amphibian populations are being threatened by human related activities including the spread of the fungal pathogen, Batrachochytrium dendrobatidis (Bd) and urbanization. With growing losses in global amphibian biodiversity, it is essential to document how amphibian populations are responding to rapid environmental changes. While most evolutionary processes, e.g. changes in allelic frequencies, may be too slow to allow adequate response to environmental changes, epigenetic modifications can rapidly translate environmental changes into adaptive phenotypic responses. Epigenetic modifications come in multiple, non-exclusive forms, the most notable being DNA methylation. Here we sought to examine variation in the frequency of DNA methylation among four tungara frog populations distributed across Gamboa, Panama; which vary in both their level of fungal presence/prevalence and urbanization. DNA samples were collected from amplexed (male–female) pairs and frequency of DNA methylation was analyzed using a methylation-sensitive amplified fragment length polymorphism protocol. We found significant variation in DNA methylation among populations, and correlations between Bd infection status and methylation patterns. Urbanization, however, had no influences on the frequency of DNA methylation. These data suggest epigenetic modifications are substantially flexible across fine-scale, environmental gradients and there appears to be possible biologically relevant links between DNA methylation and Bd infection status. Our results provide a basis for future work investigating the causal role epigenetics have in mediating phenotypic response to human-induced, environmental changes.