Spatial Variation of Skin-associated Microbiota in a Green Salamander Metapopulation

As compared to free-living microbes, host-associated (HA) microbes are unique in that they experience dispersal at both the microbial and host scales. This is particularly clear in systems where hosts experience strong barriers to dispersal, for example in host metapopulations. In these systems, HA microbes can experience dispersal limitation in moving from host to host (microbial scale dispersal). However, they can also experience dispersal limitation in moving from host habitat patch to host habitat patch (host scale dispersal). Here we use green salamanders to study the role of host metapopulation structure on the spatial patterns of skin microbiota. This species exhibits metapopulation structure wherein animals primarily inhabit rock outcrops with occasional dispersal between. We find that skin microbiota alpha diversity is relatively constant across subpopulations, but that composition changes. In particular, we find evidence of distance-decay in similarity of skin microbiota that is not evident in our environmental samples. We then discuss implications of these findings, both with reference to spatial processes governing HA microbiota as well as applied implications related to amphivian conservation. For the latter, we consider variation in antifungal community profiles across populations and what this might mean in terms of variation in susceptibility to Chytridiomycota susceptibility.