Animals host a wide variety of symbiotic microorganisms that compose their microbiomes. Recent research has focused on the beneficial functions of microbial communities that occur on amphibian skin, which includes vitamin generation and pathogen resistance. Amphibian skin microbiomes are highly variable among populations and species because they are strongly influenced by a variety of factors, such as host identity, environmental microbial community structure, temperature, and salinity. Salinity is a particularly strong environmental filter that affects microbial communities, and amphibian exposure to saltwater is increasing due to progressive salinization of freshwater wetlands resulting from increased application of road de-icing salts, sea level rise, and other factors. While it is predicted that secondary salinization will detrimentally affect amphibian communities, there are abundant reports of anuran species that can persist in saline habitats, and research indicates that exposure to saltwater can provide protection against microbial pathogens like Batrachochytrium dendrobatidis. However, very little is known about a.) How salinity affects microbial community structure on amphibian skin, b.) Whether the environmental (e.g., water, vegetation, etc.) microbial community strongly influences the microbiome of the integument, and c.) Whether microbiomes sampled from anurans from saline wetlands contained distinct and potential more pathogen resistant microbiomes than freshwater individuals.
We sampled the microbial community of the skin of Hyla cinerea (American green tree frog) following standardized swabbing protocols. We swabbed multiple individuals from several populations from coastal, saline wetlands and inland, freshwater wetlands. Mud, vegetation, and water microbial samples were also collected from each site. Relative abundance of operational taxonomic units (OTUs) based on 16S rRNA gene amplicon sequencing was used to assess bacterial community structure on the skin. Illumina sequencing revealed approximately 6000 OTUs between all samples. Our analysis of these samples suggests that microbial communities on hosts are distinct from the environmental samples suggesting that the microbial communities are host specific. We also found that the microbial communities on anuran integument are divergent among populations and according to habitat salinity. We are currently quantifying differences in the abundances of bacteria species that are commonly associated with providing beneficial anti-pathogenic services to the host (e.g., Janthinobacterium lividum). This study is among the first to investigate how skin microbial communities change along a salinity gradient in freshwater species and the first to compare the skin micro-biomes of an amphibian persisting in both saline and freshwater habitats.