The Muskox Lost a Substantial Part of Its Genetic Diversity on Its Long Road to Greenland.

The muskox (Ovibos moschatus) is the largest terrestrial herbivore in the Arctic and plays a vital role in the tundra ecosystem [1-4]. Its range, abundance, and genetic diversity have declined dramatically over the past 30,000 years [5]. Two subspecies are recognized, but little is known about the genetic structure and how this relates to the species history. One unresolved question is how and when the species dispersed into its present range, notably the present strongholds in the Canadian archipelago and Greenland. We used genotyping by sequencing (GBS) data from 116 muskox individuals and genotype likelihood-based methods to infer the genetic diversity and distribution of genetic variation in the species. We identified a basal split separating the two recognized subspecies, in agreement with isolation of the muskox into several refugia in the Nearctic around 21,000 years ago [6], near the last glacial maximum (LGM). In addition, we found evidence of strong, successive founder effects inflicting a progressive loss of genetic diversity as the muskox colonized the insular High Arctic from an unknown Nearctic origin. These have resulted in exceptionally low genetic diversity in the Greenlandic populations, as well as extremely high genetic differentiation among regional populations. Our results highlight the need for further investigations of genetic erosion in Nearctic terrestrial mammals, of which several show similar colonization histories in the High Artic.