ASSOCIATIONS BETWEEN IMMUNOGENETICS AND CUTANEOUS MICROBIAL COMMUNITY COMPOSITION IN TWO SUBSPECIES OF GIANT SALAMANDERS. Hellbender cutaneous microbiome

The complex association between hosts and their microbial symbionts requires the implementation of multiple approaches to effectively evaluate variation in host physiology. Within amphibians, population level heterogeneity in immunogenetic traits and cutaneous microbiome composition have been associated with variation in disease resistance. Variation in disease resistance and conservation status between Ozark (Cryptobranchus alleganiensis bishopi) and eastern hellbenders (C. a. alleganiensis) provides an ideal model system to assess variation in immunological traits and microbiomes. Ozark hellbenders have experienced dramatic declines throughout their limited range, are currently listed as federally endangered, and experience chronic wound retardation that is not evident in the sister subspecies. Previous microbial investigations indicate substantial differentiation in the composition of the skin microbiome of both hellbender subspecies, but it is not clear if these results are linked to diversity in the major histocompatibility complex (MHC) genes. I characterized the MHC class IIB and the skin microbiome of eastern and Ozark hellbenders in Missouri, where both subspecies co-occur though not sympatric. I compared the microbiome composition and MHC diversity between both subspecies and investigated whether individual-level MHC diversity was associated with microbiome composition. Overall MHC IIB diversity was reduced in Ozark hellbenders compared to the eastern subspecies. My multivariate statistical comparisons detected compositional differentiation between the two subspecies, despite the sharing of a core set of bacterial lineages within their skin microbiome. MHC IIB allele presence/absence and divergence significantly defined grouping of hellbender microbial communities in at least two populations. Differentiation of the skin microbiome and MHC IIB genes between Ozark and eastern hellbenders suggest that differences exist in immunity between subspecies. This study demonstrates how simultaneous assessments of host genetic traits and microbial symbiont communities can inform patterns of microbial community structure in natural systems. In addition, Ozark hellbender conservation programs should consider additional assessment and management of the MHC.