Determining demographic and genetic structure of sedentary and migratory bears (Ursus arctos) within Eastern Anatolia using genome-wide genetic markers

Large carnivores are known for altering their life-history strategies in response to environmental change. One such shift was recently discovered in brown bears (Ursus arctos) within Eastern Anatolia, where the availability of city dumps as a food source has led to the evolution of two distinct life strategies: sedentary bears that use city dumps as a primary food source and migratory bears that avoid the dump and migrate in search of food. Understanding the demographic and genetic processes that have led to the establishment of these life-history strategies is vital for predicting which life history strategy will dominate in the future and the overall impact of anthropogenic pressures on wild carnivores forced to live in human-dominated landscapes. Adaptive and genomic processes responsible for the two life-history strategies were determined using genotype data from 57 blood samples collected from captured bears, 31 of which were fitted with satellite collars and tracked almost for one year, providing information on bears' movement ecology and migratory behavior. We found that the Eastern Anatolian brown bear population is genetically highly differentiated and isolated from other world populations but contains high genetic diversity. Historical demography showed a recent dramatic increase in the effective population size of the bear population in Eastern Anatolia while relatedness analysis showed higher coefficient of kinship and sib-ship in sedentary bears utilizing the garbage dump. We also determined several genomic regions and distinct genotypes associated with sedentary and migratory behavior and strong signatures of positive selection at these loci. Outlier loci were associated with a number of transcript modifier genes, including the first exon of CCRL2, a gene that regulates immune response. Moreover, polygenic discrimination studies revealed 464 SNPs distributed throughout the genome actively contributing to difference in movement behaviorand could reliablt predict movement behavior in un-classified individuals. Gene ontology for these discriminatory SNPs revealed that the detection of sensory and chemical stimuli was the most important function that differentiated sedentary and migratory bears. Collectively our results indicate that adaptation to human-oriented landscapes in the East Anatolian brown bear population may have a strong genetic basis and emphasizes the importance of evolutionary genomics for understanding how species survive and adapt to human-mediated global change.