Molecular systematics of the Sicista tianschanica species complex: a contribution from historical DNA analysis

The Tianshan birch mouse Sicista tianschanica is an endemic of the Central Asian mountains and has previously been shown to include several karyomorphs ("Terskey", "Talgar", "Dzungar"); however, the taxonomic status of these forms has remained uncertain. We examined the genetic variation in S. tianschanica based on historical DNA samples from museum collections, including the type series. Mitochondrial and nuclear data indicated that the species complex includes two major clades: Northern (N) and Southern (S) (cytb distance 13%). The N clade corresponds to the "Dzungar" karyomorph (Dzungar Alatau, Tarbagatay). The S clade is comprised of four lineages (S1-S4) divergent at 6-8%; the relationships among which are resolved incompletely. The S1 lineage is found in eastern Tianshan and corresponds to the nominal taxon. The S2 is distributed in central and northern Tianshan and corresponds to the "Terskey" karyomorph. The S3 is restricted to Trans-Ili Alatau and belongs to the "Talgar" karyomorph. The S4 is represented by a single specimen from southeastern Dzungar Alatau with "Talgar" karyotype. No interlineage gene flow was revealed. The validity of S. zhetysuica (equivalent to the N clade) is supported. Based on genetic and karyotypic evidence, lineages S2 and S3 are described as distinct species. The status of the S4 requires further investigation.