Over the last several hundred years, donkeys have adapted to high-altitude conditions on the Tibetan Plateau. Interestingly, the kiang, a closely related equid species, also inhabits this region. Previous reports have demonstrated the importance of specific genes and adaptive introgression in divergent lineages for adaptation to hypoxic conditions on the Tibetan Plateau. Here, we assessed whether donkeys and kiangs adapted to the Tibetan Plateau via the same or different biological pathways and whether adaptive introgression has occurred. We assembled a de novo genome from a kiang individual and analyzed the genomes of five kiangs and 93 donkeys (including 24 from the Tibetan Plateau). Our analyses suggested the existence of a strong hard selective sweep at the EPAS1 locus in kiangs. In Tibetan donkeys, however, another gene, i.e., EGLN1, was likely involved in their adaptation to high altitude. In addition, admixture analysis found no evidence for interspecific gene flow between kiangs and Tibetan donkeys. Our findings indicate that despite the short evolutionary time scale since the arrival of donkeys on the Tibetan Plateau, as well as the existence of a closely related species already adapted to hypoxia, Tibetan donkeys did not acquire adaptation via admixture but instead evolved adaptations via a different biological pathway.
在过去的几百年里，生活在青藏高原的家驴已经适应了高海拔的环境。有趣的是，同属于马科的近缘物种藏野驴也居住在这一地区。以往的研究阐述了不同谱系中特定基因的适应性渐渗对青藏高原低氧环境适应有重要的作用。在这项研究中，我们对藏家驴和藏野驴是否通过相同或不同的生物途径适应高原环境，以及是否发生了适应性渐渗现象展开了研究。我们从头组装了一个藏野驴的基因组，结合5个藏野驴和93个家驴(包括24个藏家驴)的基因组重测序数据展开了分析研究。分析表明，藏野驴EPAS1基因存在强的选择性清除信号；然而，藏家驴的高原适应，则是另一与高原适应相关的基因EGLN1，参与它们适应高海拔环境。此外，针对基因流的分析，我们未发现藏野驴和藏家驴中与高原适应相关的基因流动。我们的研究结果表明，尽管家驴在青藏高原的进化时间较短，且存在一个已经适应高原低氧环境的近缘物种，但藏家驴并没有通过与藏野驴的适应性渐渗来获得对高原的适应性，藏野驴与藏家驴这两个物种通过不同的生物途径进化出了对高原的适应能力。.
Keywords: Adaptation; Donkey; High altitude; Kiang; Selection.