The Stummer’s Racerunner (Eremias stummeri Wettstein, 1940) does occur in Northwest China
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The status of Eremias stummeri in China has been a matter of controversy for over two decades, although it is well acknowledged that this species occurs in Northeast Kyrgyzstan and Southeast Kazakhstan. To date, whether its occurrence extends to the adjacent Chinese region (possibly in the Ily River Valley) has not been confirmed yet. To overcome constraints on field surveys imposed by the region’s remoteness and rugged terrain, we targeted areas of further field inventories by estimating the potential distribution of the species. Ecological niche modeling (ENM) enabled us to predict a continuous distribution area from Kazakhstan to the Chinese part of the Ily River Valley in Zhaosu county for the species’ occurrence. We conducted extensive field surveys in the predicted area. In 2017, for the first time, the occurrence of E. stummeri in China was confirmed with a single find in Zhaosu county. Further morphological and multilocus phylogenetic analyses congruently supported the taxonomic status of the recently discovered population as E. stummeri. In contrast to its distribution continuity between Kazakhstan and China, the ENM indicates distribution discontinuity between Kazakhstan and Kyrgyzstan. This geographic distribution pattern of E. stummeri is supported by morphological and molecular evidence, which highlights that individuals from China and Kazakhstan are more closely related to each other than to those from Kyrgyzstan. The mismatch between mitochondrial and nuclear phylogeographic pattern implies that historical mitochondrial introgression occurred from E. stummeri individuals from Kyrgyzstan to those from Kazakhstan.