Complete mitochondrial genomes of Chionomys roberti and Chionomys nivalis (Mammalia: Rodentia) from Turkey: Insight into their phylogenetic position within Arvicolinae

The complete mitochondrial DNA (mitogenome) sequences of Chionomys nivalis and C. roberti were first presented as reference mitogenomes by the current study using Long-Range PCR and Next-Generation Sequencing. The structure and organization of the circular mitogenomes were similar for each species. Each mitogenome included 22 tRNA genes, two rRNA genes, 13 protein-coding genes (PCGs), a control region (D-loop), and an origin of the light-strand region (OL), with the mitogenome lengths of 16.293 for C. nivalis and 16.300 for C. roberti. Phylogenetic analyses based on whole mitogenomes sequences allowed us to see better the relative position of the Chionomys within Arvicolinae. According to this, Chionomys was in a close phylogenetic relationship with Microtus rather than Arvicola. Contrary to the results of past studies, the relative positions of the species within Chionomys varied in the cytochrome b sequence-based phylogenetic analyses. Additionally, the presence of 10 genetic lineages determined by previous works within C. nivalis was approved. Among them, the Central Taurus lineage genetically was the lineage most distant from others. On the other hand, Turkish C. roberti specimens were clustered with the Transcaucasian specimens (Datvisi- Georgia and Alania-North Ossetia-Russia) splitting from other GenBank specimens of Russia and Georgia. Divergence-time analyses demonstrated that the first appearance of Arvicolinae dates back to the Early Pliocene (4.96 mya, 95% HPD: 4.09-5.82, BPP: 1), compatible with the past findings. Also, it was detected that the split of Arvicola / Chionomys + Microtus took place at the beginning of the Quaternary period (2.35 mya, 95% HPD: 1.97-2.75, BPP: 0.98). This corresponded to the Early Pleistocene divergence (approximately 2.4 mya) of these three genera suggested by the fossil record. In addition to this, molecular dating analyses demonstrated that the divergence between C. nivalis and C. roberti occurred in the Middle Pleistocene (1.06 mya, 95% HPD: 0.87-1.25, BPP: 1). Further studies using other molecular markers are needed to make definite judgments on the taxonomy and evolution of Chionomys.