The Hidden Ecosystem: the Microbial World of Red-Backed Salamanders

Abstract

Each organism has a complex microbiota that protects the organism from pathogenic microbes, while simultaneously occupying residency on the surface of the host. There are several factors that can contribute to microbial diversity, such as anthropogenic, abiotic, and biotic factors within their habitat. Red-backed salamanders (Plethodon cinereus) are found across the northeastern US in a variety of different habitats. We aimed to collect and culture salamander epidermal microbes along an urbanization gradient (Point au Roche State Park, Rugar Woods, and the Paul Smiths VIC- control and 2-aged silviculture stand) to evaluate microbial diversity patterns. At each site, 15 salamanders were located under microhabitat (e.g., rocks, logs, leaf litter), weighed, and measured before swabbing dorsoventral surfaces. Swabs were streaked across plates and were allowed to grow at ambient temperatures for a week. Morphotype diversity was calculated based on the richness and abundance of colonies on plates across sites. Samples of both common and unique morphotypes were sent off for sequencing. Salamanders were more commonly found under rocks at Rugar Woods as compared to all other sites respectively. Additionally, red-backed salamanders at Point au Roche were notably larger than Paul Smiths VIC and Rugar Woods. Bacterial morphotype richness was greatest and least at Rugar Woods (urban) and Point au Roche State Park (agriculture), respectively. Findings at Rugar Woods suggest that rocky substrate may support greater microbial richness as compared to coarse woody debris. Common salamander bacteria include Microbacterium liquefaciens, Pseudomonas moraviensis, Chryseobacterium scophthalmum, and Stenotrophomonas rhizophilia all species associated with soil, water, and plant rhizosphere. Chryseobacterium scophthalmum is associated with amphibian disease and S. rhizophilia is known to possess anti-chytrid and other antifungal properties. Our research sheds light on how landscape management, specifically understory conditions and complexity, can influence salamander condition and microbial diversity and potentially influence disease risk within the herpetofaunal community.