Mapping pathogen distributions and population connectivity of a sentinel Arctic species, the polar bear (Ursus maritimus) across a changing North American Arctic

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Tschritter, Christina
Molecular Ecology , Wildlife disease surveillance , population genetics
Large-scale environmental shifts are expanding pathogen distributions making many northern species more vulnerable to disease. To understand such rapidly changing host-pathogen dynamics and potentially mitigate impacts of novel pathogens on northern peoples and ecosystems, I quantify population connectivity and pathogen presence in a sentinel Arctic species, the polar bear (Ursus maritimus). Polar bears are apex predators that can provide insight into pathogen distribution and prevalence across marine and terrestrial ecosystems. The focus of my dissertation was to develop molecular tools to monitor polar bear populations and to promote co-management through non-invasive and harvest-based sampling. More specifically I aimed to: (i) Delineate polar bear population structure using genome-wide panels of Single Nucleotide Polymorphic markers (SNPs) to interpret population connectivity that might impact pathogen spread; (ii) Develop and validate a sensitive multiplexed, magnetic-capture, and digital PCR tool for surveillance of five zoonotic pathogens (three bacteria Erysipelothrix rhusiopathiae, Francisella tularensis, and Mycobacterium tuberculosis complex (MTBC), and two parasites T. gondii and Trichinella spp.) relevant to wildlife and human health; and (iii) Quantify the spatial distributions of focal pathogens in polar bear tissues and observe associations between pathogen detections and predictors. Despite the mobility of polar bears and their large home ranges, I found three population clusters that coincide with Arctic ice ecoregions. I made novel pathogen detections (first detection of E. rhusiopathiae in a polar bear, first molecular detection of F. tularensis in the tundra, and the first detection of a MTBC member in Arctic wildlife) and provide insights on how populations might respond to future exposure to novel pathogens. Overall, we found that harvest season and human settlements were important predictors of presence for some pathogens. I envision the establishment of a long-term harvest-based monitoring program that incorporates the powerful molecular tools that we have created, enabling territorial governments to monitor changes in prevalence and/or the geographic advance of select pathogens. The continuation and expansion of this work into a monitoring program would present an unprecedented opportunity to provide critical, real-time, and community-based disease surveillance across the Arctic and ultimately improve opportunities for the co-management of the polar bear species.
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