Copy Number Variation in the Amylase Gene (AMY) in the Brown Bear (Ursus arctos), Based on Whole Genome Resequencing Data.

Copy number variation (CNV) in gene loci in animals can be driven by adaption to the environment. The relationship between CNV in genes for amylase (AMY), which hydrolyzes starch, and dietary adaptation has been well studied. Copy number (CN) of AMY is higher in human populations with high-starch diets, compared with those with low-starch diets. Although CNV in AMY has been reported in humans and some domestic animals, there have been few studies of animals in the wild. The brown bear (Ursus arctos), widespread in the Northern Hemisphere, shows large dietary variation among individuals and groups. Brown bear population genetic structures are associated with the dispersal history due to climate change over the past few tens of thousands of years, and this together with dietary variation should have led to CNV in AMY. In this study, we investigated CNV in AMY in brown bears worldwide by using whole genome sequencing data. We detected AMY CNV among regional groups. AMY CN was similar among brown bears in geographically proximate populations, such as between Hokkaido (Japan) and East Asia, and between the North America mainland and the ABC islands. CNs were smaller in bears from East Asia, including Hokkaido, compared to those from other regions across brown bears' distribution. Our results suggest that CNs of AMY reflect the population demographic history of brown bears after the Last Glacial Maximum.