Genome-Wide Investigation of Admixture in Polar and Brown Bears

Recent advances in next-generation sequencing technology have opened doors to conservation and population genomic studies of wildlife species, for which only limited genetic resources exist. We are using a next-generation sequencing strategy to detect genome-wide single nucleotide polymorphisms (SNPs) in bear species. Based on distinct differences in morphology, physiology, and behavior, polar bears and brown bears are recognized as separate species. In particular, the polar bear is specialized to a life on the sea ice, and as such represents an excellent species for investigating the response of Arctic animals to global climate change. Yet, data from mitochondrial genomes indicate an intricate relationship between the two species suggesting a maternal origin of polar bears from within brown bears. Using both deep and shallow next-generation sequencing, we have discovered thousands of genome-wide SNPs, which may not only provide a potential genomic window into polar bear adaptation to a high-Arctic climate but also facilitate evolutionary genomic studies among bear populations. Sequencing amplified SNPs, we generated digitally genotyped markers where inter- and intra-individual heterozygosity can be detected with high sensitivity. Preliminary data indicate admixture in the bear genomes and possible hybridization during early stages of polar bear evolution. Our approach is highly flexible since more SNPs and more samples can easily be added throughout the course of the project, without need for re-development of costly SNP arrays. Using this model, single investigators can produce high numbers of genome-wide variable markers to investigate ecological and evolutionary genomics of wildlife species.