Zokors in the genus Eospalax, which are endemic to northern and western China, are subterranean rodents that inhabit various niches, including grasslands, high-altitude meadows, forests, and farmlands. Six species in Eospalax were described a century ago but their taxonomy and phylogeny remain controversial. In this study, we performed high-depth whole-genome sequencing of 47 zokor samples, comprising all six previously described species. Genomic analyses revealed a reliable and robust phylogeny of Eospalax and supported the validity of the six named species. According to the inferred phylogenetic relationships, Eospalax first divergent into two clades in the early Pliocene (ca. 4.68 million years ago (Ma)), one inhabiting the high-altitude Qinghai-Xizang (Tibet) Plateau (QTP) and adjacent regions, and the another inhabiting the low-altitude Loess Plateau and Qinling-Daba Mountains. The most recent divergences occurred between E. baileyi and E. smithii and between E. rufescens and E. rothschildi in the late Pliocene (ca. 2.09 and 2.19 Ma, respectively). We also collected specimens of zokors in the southern Hengduan Mountains (Muli County, Sichuan Province), far from the known distributions of all other zokors. Morphological and molecular analyses strongly suggested that the specimens represent a new species, formally described here as Eospalax muliensissp. nov. The new species belongs to the high-altitude clade and diverged from closely related species (ca. 4.22 Ma) shortly after the first divergence in Eospalax. Interestingly, Eospalax muliensissp. nov. possesses more supposedly plesiomorphic characters, suggesting a possible origin of the genus in the Hengduan Mountains.
凸颅鼢鼠属（Eospalax）是一类严格地下生活的啮齿类动物，为中国特有属，主要分布于中国西部与北部的草原、高海拔草甸、森林和农田等生境。早在一个世纪前，研究者就已对凸颅鼢鼠属的6个物种进行了描述，但至今其分类学和系统发育关系仍存在争议。该研究对47个鼢鼠样本进行了高深度的全基因组测序，并构建了高可信度且稳健的系统发育关系。研究结果支持所有6个已命名物种的有效性。全基因组分析显示，凸颅鼢鼠属在上新世早期（约468万年前）首先分化为两个支系：一支栖息在青藏高原及其邻近的高海拔地区；另一支生活在黄土高原和秦岭大巴山脉低海拔地区。凸颅鼢鼠属最近的分化发生在高原鼢鼠（E. baileyi）和斯氏鼢鼠（E. smithii）之间以及在秦岭鼢鼠（E. rufescens）和罗氏鼢鼠（E. rothschildi）之间，时间为上新世晚期（分别约209和219万年前）。此外，我们还在远离鼢鼠所有已知分布地的横断山脉南部（四川省木里县）采集到了鼢鼠标本。形态学和分子水平的分析都强烈表明这些标本代表一新种，在此正式描述为木里鼢鼠Eospalax muliensissp. nov.。木里鼢鼠属于高海拔支系，其在约422万年前，凸颅鼢鼠属属内第一次分化后不久，与其近缘物种发生划分。有意思的是，相比于凸颅鼢鼠属的其他物种，木里鼢鼠保留了更多假定的祖先型性状，提示凸颅鼢鼠属有可能起源于横断山脉。
Keywords: Eospalax; Hengduan Mountains; New species; Phylogenomic analyses; Zokor.