Little Overlap in Symbiotic Bacteria of Coquí Frogs in Hawaii and Puerto Rico

ABSTRACT Amphibian skin bacteria are important for host health by protecting against pathogens, but communities can vary greatly among host populations, influenced by environmental factors, habitats, and ecological interactions. Understanding this variation is key to studying how amphibians adapt and remain healthy across diverse environments. In this study, we sampled skin bacteria on coquí frogs ( Eleutherodactylus coqui ) from two sites in each of two regions: Puerto Rico, where they are native, and Hawaii, where they are introduced. We tested the hypothesis that bacterial communities differ between regions but are relatively more similar within each region. We also expected that comparing bacteria at the genus level would show more similarity than at the level of unique sequences, indicating the importance of microdiversity and functional roles. Beta diversity provided mixed support for these hypotheses, showing differences between sites that became less pronounced within each region at the bacterial genus level. Interestingly, one Hawaiian site stood out as distinct in multiple analyses. Despite predicted variation, we expected to find core (prevalent) bacteria shared across sampling locations, which was confirmed for a few taxa, suggesting they play important functional roles and may be selected by the host. Microbial community variation on coquí frogs is influenced by their habitat‐generalist nature, with habitat likely affecting environmental bacterial sources, but can also be shaped by invasion history, disease, development stages, and season. This research enhances our understanding of how environmental and biological factors shape amphibian microbiomes, which is valuable for conservation efforts and studying invasive species.