Ancient DNA perspectives on North American cervids identify fluctuations in genetic diversity

Abstract

North American fauna has experienced major changes over the last two million years. Glacial cycles, animal migrations, peopling waves, and, more recently, European colonisation, caused demographic fluctuations, divergence, and wildlife extinctions. Caribou (Rangifer tarandus), moose (Alces alces), wapiti (Cervus canadensis), white-tailed (Odocoileus virginianus) and mule deer (O. hemionus) are the five extant cervids in Northern America, with unique dispersal patterns and conservation statuses. Here, we used DNA analysis of ancient, historical and modern individuals of these Cervidae to retrace evolutionary processes through time. We show that present-day eastern Canada caribou share ancestry with a 30-thousand-year-old sample from western Canada consistent with the species' complex dispersal history as suggested by literature. Our results suggest rapid expansion of moose following their arrival on the continent ~15 thousand years ago. Data on wapiti shows a recent loss of diversity consistent with its large-scale extirpation after European colonisation. Results on Odocoileus species are in line with their recognised mito-nuclear discordance. Our results exemplify the utility of chronological sampling to gain a better understanding of how external pressures drive genomic changes.