Semester of Graduation
Master of Science (MS)
Renewabke Natural Resources
Reticulated flatwoods salamander (Ambystoma bishopi) populations began decreasing dramatically in the late 1900s. Contemporary populations are small, isolated, and may be susceptible to inbreeding and reduced adaptive potential because of low genetic variation. Genetic variation at immune genes is especially important as it influences disease susceptibility and adaptation to emerging infectious pathogens, a central conservation concern for declining amphibians. Connectivity between isolated populations is also vital to maintain genetic diversity and avoid inbreeding. I collected tissue samples from across the extant range of this salamander to examine genetic variation and population structure in: immune genes broadly (immunome), the major histocompatibility complex (MHC) class Iα and IIβ exons, as well as the mitochondrial control region. I also screened for ranavirus, a pathogen associated with amphibian declines worldwide. Overall, I found low MHC variation when compared to other amphibian species but mitochondrial diversity similar to other Ambystomatids. I also found moderate diversity in the immunome with possible gene duplication. I did not detect ranavirus at any site. MHC class Iα sequencing revealed only three highly similar alleles while MHC class IIβ sequencing found five alleles. However, unique variation still exists across this species’ range with private alleles at several sites. I hypothesize that a combination of factors may have contributed to low MHC diversity, specifically, a historic disease outbreak and/or a population bottleneck. Ultimately, MHC data indicates that the reticulated flatwoods salamander is at an elevated risk from infectious diseases due to low levels of immunogenetic variation necessary to combat novel pathogens. Population structure and migration between major sites was calculated using all three genetic marker types (immunome, MHC, and mitochondria). Population structure for immunome and MHC data was low between major breeding sites, but mitochondrial structure was higher. This pattern is indicative of male biased dispersal with females dispersing at a lower rate than males. Using program Migrate-N and BayesAss I calculated migration rates and found historic gene flow between salamander breeding sites. Since there is low population structure and historic migration between sites, I suggest human mediated dispersal of this species to re-establish gene flow and extirpated populations.
Williams, Steven Tyler, "Immune Gene Diversity and Populations Structure of Reticulated Flatwoods Salamander (Ambystoma bishopi)" (2019). LSU Master's Theses. 5014.
Available for download on Wednesday, October 28, 2020