Columbia spotted frogs (Rana luteiventris) have characteristic microbiota that may be shaped by their skin peptides and the environment
Global amphibian declines due to the fungal pathogen Batrachochytrium dendrobatidis (Bd) have led to questions about how amphibians defend themselves against skin diseases. Two amphibian defense mechanisms are antimicrobial peptides (AMPs), a component of amphibian innate immune defense, and symbiotic skin bacteria, which can act in synergy. We characterized components of these factors in four populations of Columbia spotted frogs (Rana luteiventris) to investigate their role in disease defense. We surveyed the ability of their AMPs to inhibit Bd, skin bacterial community composition, skin metabolite profiles, and presence and intensity of Bd infection. We found that AMPs from R. luteiventris inhibited Bd, but inhibition did not correlate with Bd. R. luteiventris had two prevalent and abundant core bacteria: Rhizobacter and Chryseobacterium. The bacterium Rhizobacter was negatively correlated with AMP's ability to inhibit Bd, but not associated with Bd. There was no relationship between metabolites and Bd. Bacterial communities and Bd were affected by location, which suggests a strong environmental influence.  R. luteiventris are dominated by consistent core bacteria, but also house transient bacteria that are infrequent, rare and site specific. Our emergent hypothesis is that host control and environmental factors are largely shaping the bacterial communities on R. luteiventris.