White-tailed deer population structure in Georgia
McGraw, Sabrina Nicole
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Hemorrhagic disease (HD) is the most significant infectious disease of white-tailed deer (WTD) in the southeastern USA. Acute fatal HD is most often associated with northern latitudes, and results from experimental infection studies provide evidence for the role of innate host factors in HD resistance. In Georgia (GA), a consistent geographic pattern of mortality has prompted speculation regarding the potential role of spatial variation in host innate factors introduced to the state during extensive restocking efforts to reestablish the species following near extirpation in the early 20th century. This study estimated the population genetic structure of white-tailed deer in GA using mitochondrial and microsatellite markers, compared extant deer from GA and Wisconsin (WI) to identify residual genetics from source populations, and evaluated Georgia deer for disparities in allelic diversity at the major-histocompatability (MHC) class I heavy chain locus. Metapopulations across the state demonstrate varying degrees of genetic isolation, and two isolated populations (Blue Ridge Mountains, barrier islands; p<0.05 for mtDNA) are associated geographically with increased HD mortality reports. Of 16 mitochondrial D-loop control haplotypes identified in 21 Wisconsin WTD, 7 (43.8%) were identical to haplotypes found in GA WTD, and were associated spatially with counties where WI deer were introduced in the mid-1900s. No significant differences were found in allelic diversity at the MHC Class I heavy chain locus across sampled locations. In order to appreciate purportedly high level of spatial genetic heterogeneity in Georgia white-tailed deer attributed to extensive restocking, we compared genetic diversity and structure of white-tailed deer in two states. Mitochondrial sequences were compared between similarly sized areas of both Georgia (restocked) and Wisconsin (no restocking history). Although the number of haplotypes identified in each area were similar, they were significantly more variable in Georgia. Our findings suggest fine-scale genetic structure in GA WTD, influenced by introduction history, with isolated metapopulations corresponding geographically with areas of increased HD mortality. However, host-pathogen dynamics are complex, and host innate factors represent only a portion of potential variables influencing the geographic distribution of HD mortality in GA.