Bacterial Skin Assemblages of Sympatric Salamanders are Primarily Shaped by Host Genus

Hill, Aubree; Grisnik, Matthew; Walker, Donald

ABSTRACT: Bacterial assemblages on the skins of amphibians are known to affect pathogen resistance and other important physiological functions in the host. Host-specific factors and the environment play significant roles in structuring skin assemblages. This study used high-throughput 16S rRNA sequencing and multivariate analyses to examine differences in skin-bacterial assemblages from 246 salamanders belonging to three genera in the lungless family Plethodontidae along multiple spatial and temporal gradients. Composition and α- and β-diversity of bacterial assemblages were defined, and the relative influences of host- versus environment-specific ecological factors were evaluated. At the broadest spatial scale, host genus and sampling site were both predictive of skin assemblage structure, but host-specific variation was more influential after controlling for the marginal effects of site, as well as nestedness of site. Furthermore, assemblage similarity within each host genus did not change with increasing geographic distance. At the smallest spatial scale, site-specific climate analyses revealed different relationships to climatic variables for each of the three genera, and these relationships were determined by host ecomode. Variation in bacterial assemblages of terrestrial hosts correlated with terrestrial climatic variability, and this pattern decayed with increasing water dependence. Results from this study highlight host-specific considerations for researchers studying wildlife diseases in co-occurring, yet ecologically divergent, species.