The muskox lost a substantial part of its genetic diversity on its long road to Greenland. Muskox population genetics

The muskox (Ovibos moschatus) is the largest terrestrial herbivore in the Arctic and plays a vital role in the tundra ecosystem. Its range, abundance and genetic diversity has declined dramatically over the past 30,000 years. 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, 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 Neartic terrestrial mammals, of which several show similar colonization histories in the High Artic.

麝牛（Ovibos moschatus）是北极地区体型最大的陆生植食性动物，在苔原生态系统中发挥着至关重要的作用。过去3万年间，其分布范围、种群丰度与遗传多样性均出现了大幅下降；目前学界已确认该物种存在2个亚种，但人们对其遗传结构及其与该物种种群演化历史的关联仍知之甚少，其中一项尚未解决的科学问题是：该物种是如何、在何时扩散至当前的分布范围，尤其是当前作为其核心分布区域的加拿大群岛与格陵兰岛。本研究采集了116头麝牛的测序分型（genotyping by sequencing, GBS）数据，并采用基于基因型似然值的分析方法，对该物种的遗传多样性与遗传变异分布格局进行了推断。我们鉴定出了分隔两个已确认亚种的基础分化事件，这与约2.1万年前末次冰盛期（last glacial maximum, LGM）前后，麝牛在新北区（Nearctic）的多个冰期避难所（refugia）发生隔离的假说相符。此外，我们发现了强烈且连续的奠基者效应（founder effects）的相关证据：当麝牛从未知的新北区起源地殖民至孤立的高北极群岛区域时，这种效应导致其遗传多样性逐步丧失，最终造成格陵兰种群的遗传多样性极低，且不同区域种群间的遗传分化程度极高。本研究结果凸显了针对新北区陆生哺乳动物开展遗传侵蚀状况进一步研究的必要性——其中多个类群在高北极地区都存在类似的殖民演化历史。