Phylogenetic relationships of the zokor genus Eospalax (Mammalia, Rodentia, Spalacidae) inferred from whole-genome analyses, with description of a new species endemic to Hengduan Mountains

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 muliensis sp. 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 muliensis sp. nov . possesses more supposedly plesiomorphic characters, suggesting a possible origin of the genus in the Hengduan Mountains.