The interactions between vertebrate hosts and their microbial communities have recently become a subject of interest. In particular, research on amphibian skin microbiota has focused on identifying bacterial taxa capable of deterring a pathogenic chytrid fungus responsible for massive mortality events. However, it remains unclear how soil pH and rainfall patterns (two factors known to shape soil bacterial communities) affect the amphibian skin bacterial communities, and the overall function of the amphibian skin microbiota remains unexplored. We sampled skin microbial communities (N=89) from three sympatric frog species before and after the onset of the wet season in one site, and we sampled one frog species across an environmental gradient in the Panama Canal. We hypothesized: (1) soil pH and the onset of the wet season to have an effect on the frog skin microbiota because amphibians require environmental reservoirs, such as forest soil, to maintain diverse skin bacterial communities; and (2) variation in microbial functional groups to be associated with pH and rainfall as skin microbial community shifts are ecologically relevant to the frog host.
Results/Conclusions
We found that frog skin microbial community structure varied across a soil pH gradient and was associated with the onset of the wet season, and that these community shifts corresponded with changes in microbial functional group (predicted using the Functional Annotation of Prokaryotic Taxa database). We also found that alpha diversity (estimated with Shannon’s diversity index, which considers both number and evenness of bacterial species within a sample) does not always correlate with microbial functional group diversity, challenging widespread assumptions linking higher bacterial alpha diversity to higher bacterial functional groups diversity. Overall, our results suggest that the frog host’s metabolic requirements facilitated by bacteria follow seasonal patterns and that these requirements may be site-specific.