Characterization of Major Histocompatibility Complex (MHC) DRB Exon 2 and DRA Exon 3 Fragments in a Primary Terrestrial Rabies Vector (Procyon lotor)

The major histocompatibility complex (MHC) presents a unique system to explore links between genetic diversity and pathogens, as diversity within MHC is maintained in part by pathogen driven selection. While the majority of wildlife MHC studies have investigated species that are of conservation concern, here we characterize MHC variation in a common and broadly distributed species, the North American raccoon (Procyon lotor). Raccoons host an array of broadly distributed wildlife diseases (e.g., canine distemper, parvovirus and raccoon rabies virus) and present important human health risks as they persist in high densities and in close proximity to humans and livestock. To further explore how genetic variation influences the spread and maintenance of disease in raccoons we characterized a fragment of MHC class II DRA exon 3 (250bp) and DRB exon 2 (228 bp). MHC DRA was found to be functionally monomorphic in the 32 individuals screened; whereas DRB exon 2 revealed 66 unique alleles among the 246 individuals screened. Between two and four alleles were observed in each individual suggesting we were amplifying a duplicated DRB locus. Nucleotide differences between DRB alleles ranged from 1 to 36 bp (0.4–15.8% divergence) and translated into 1 to 21 (1.3–27.6% divergence) amino acid differences. We detected a significant excess of nonsynonymous substitutions at the peptide binding region (P = 0.005), indicating that DRB exon 2 in raccoons has been influenced by positive selection. These data will form the basis of continued analyses into the spatial and temporal relationship of the raccoon rabies virus and the immunogenetic response in its primary host

Genetic analysis reveals hidden threats and new motivation for conservation translocation of black-tailed prairie dogs at the northern limit of their range

Biodiversity loss continues at unprecedented rates; to slow loss, conservation practitioners are working to remove species from risk of extinction. But, even when species are no longer at risk of extinction, they likely exist in small, isolated populations, especially at range edges, and their long-term persistence is uncertain. The northernmost population of the black-tailed prairie dog (Cynomys ludovicianus), located in Grasslands National Park, Saskatchewan, Canada, is potentially isolated from the core of the prairie dog range and has experienced dramatic population fluctuations. To better understand the genetic health of this population, we genotyped 566 individuals alongside individuals from Montana (N = 48) and South Dakota (N = 40), at 15 microsatellite loci. We also generated over 1000 base pairs of mtDNA sequence data for a subset of individuals from each of these three locations. The microsatellite data indicate that the Saskatchewan population has extremely low variability (HO = 0.231), and a high level of inbreeding (FIS = 0.14) compared to other prairie dog populations. Analysis of population structure indicates that the Saskatchewan population is isolated from the black-tailed prairie dog range. However, data from the mtDNA indicates the Saskatchewan population was connected to Montana in the recent past. Considering these results, it is important to evaluate management strategies such as genetic rescue via translocations to increase diversity and circumvent negative impacts of inbreeding. While translocating individuals presents challenges, we believe this may be the best option for Saskatchewan prairie dogs given the continuing impacts of climate change and disease

Genetic population structure of invasive raccoons (Procyon lotor) in Hokkaido, Japan: Unique phenomenon caused by pet escape or abandonment

Phylogeographic studies can resolve relationships between genetic population structure of organisms and geographical distributions. Raccoons have become feral in Japan, and in Hokkaido island, they have been rapidly increasing in number and spreading since the 1970s. We analyzed mitochondrial (mtDNA) and microsatellite DNA to understand the current phylogenetic distribution and invasive founder events. Overall, Hokkaido raccoons maintained high genetic diversity (i.e., the level of heterozygosity was comparable to the original habitat, North America). Based on mtDNA distribution and microsatellite diversity, Hokkaido raccoons were divided into six management units. However, mtDNA haplotype distributions and genetic structures based on microsatellites did not always correspond to each other (e.g., two geographically and genetically separated populations showed similar mtDNA distributions). In addition, a high degree of genetic admixture was observed in every unit, and the degree of genetic differentiation was low even between regions separated by long distances. Compared with other countries in Europe where genetic distribution of introduced raccoons is more clearly structured, the current results represent a unique and complex phenomenon of pet escape/abandonment in Hokkaido: i.e., genetically related colonies were introduced into multiple regions as founder events, resulting in the current state in which raccoons are not clearly genetically differentiated even 40 years after introduction