To predict species responses to anthropogenic disturbances and climate change, it is reasonable to use species with high sensitivity to such factors. Snow sheep (Ovis nivicola) could represent a good candidate for this; as the only large herbivore species adapted to the cold and alpine habitats of northeastern Siberia, it plays a crucial role in its ecosystem. Despite having an extensive geographical distribution among all ovine species, it is one of the least studied. In this study, we sequenced and analysed six genomes of snow sheep in combination with all other wild sheep species to infer key aspects of their evolutionary history and unveil the genetic basis of their adaptation to subarctic environments. Despite their large census population size, snow sheep genomes showed remarkably low heterozygosity, which could reflect the effect of isolation and historical bottlenecks that we inferred using the pairwise sequential Markovian coalescent and runs of homozygosity. F₄-statistics indicated instances of introgression involving snow sheep with argali (Ovis ammon) and Dall (Ovis dalli) sheep, suggesting that these species might have been more widespread during the Pleistocene. Furthermore, the introgressed segments, which were identified using mainly minimum relative node depth, covered genes associated with immunity, adipogenesis and morphology-related traits, representing potential targets of adaptive introgression. Genes related to mitochondrial functions and thermogenesis associated with adipose tissue were identified to be under selection. Overall, our data suggest introgression as a mechanism facilitating adaptation in wild sheep species and provide insights into the genetic mechanisms underlying cold adaptation in snow sheep.

中文翻译：

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全基因组测序揭示了野羊复杂的渐渗历史和适应亚北极气候的基础

为了预测物种对人为干扰和气候变化的反应，使用对这些因素高度敏感的物种是合理的。雪羊 ( Ovis nivicola) 可以代表一个很好的候选人；作为唯一适应西伯利亚东北部寒冷和高山栖息地的大型食草动物，它在其生态系统中发挥着至关重要的作用。尽管在所有绵羊物种中具有广泛的地理分布，但它是研究最少的物种之一。在这项研究中，我们结合所有其他野生绵羊物种对雪羊的六个基因组进行了测序和分析，以推断它们进化历史的关键方面，并揭示它们适应亚北极环境的遗传基础。尽管它们的人口普查人口规模很大，但雪羊基因组显示出非常低的杂合性，这可能反映了我们使用成对顺序马尔可夫聚结和纯合性运行推断的隔离和历史瓶颈的影响。F ₄-统计数据表明，雪羊与盘羊 ( Ovis ammon ) 和 Dall ( Ovis dalli ) 羊的基因渗入实例表明，这些物种可能在更新世更为普遍。此外，主要使用最小相对节点深度识别的基因渗入片段覆盖了与免疫、脂肪生成和形态相关性状相关的基因，代表了适应性基因渗入的潜在目标。与脂肪组织相关的线粒体功能和产热相关的基因被确定为正在选择中。总体而言，我们的数据表明基因渗入是促进野生绵羊物种适应的一种机制，并提供了对雪羊冷适应的遗传机制的见解。