Snow voles from Zard Kuh in Zagros Mts., Western Iran, were identified as distinct from the European snow vole Chionomys nivalis and described as a species new to science under the name C. layi Zykov, 2004. This description was missed in subsequent years by majority of authors dealing with the genus Chionomys, and taxonomic identity of the new species remains uncertain. In this study we conducted the first testing ever performed on taxonomic status of C. layi. We sequenced cytochrome b (1140 bp) and nuclear growth hormone receptor ghr (870 bp) in topotypes of layi and used them, together with all available haplotypes for snow voles, in phylogenetic reconstructions. Topology of phylogenetic trees accorded published results and topotypes of layi nested within reference samples of C. nivalis. They hold a supported sister position against sequences from the geographically nearby Caucasus and Alborz. Kimura-2 parameter metrics retrieved relatively low divergence (3.2 ± 0.5) between samples from the Zagros and the Alborz + Caucasus. We conclude that layi is synonymous with C. nivalis. Our results also show that the ancient refugium for the European snow vole in the Kopet Dagh was detached from the Hyrcanian refugium in the mesic mountains to the south of the Caspian Sea.

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