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Genetic variation in chromosomally polymorphic Sicista subtilis complex and related Sicista betulina species group was analysed using two mitochondrial markers (COI and Cytb). The S. subtilis group is shown to include six lineages, five of which correspond to species currently recognized based on cytogenetic and genetic data: Sicista nordmanni, Sicista trizona, S. subtilissensu stricto, Sicista severtzovi and Sicista cimlanica. A previously unknown genetic lineage of S. subtilis was found in the North Caucasus. The existence of two divergent lineages within Sicista strandi is supported. It is suggested that the speciation rate in Sicista was strongly affected by rapid chromosomal evolution. [ABSTRACT FROM AUTHOR]

Phylogeny of birch mice is estimated using sequences of ten nuclear genes and one mitochondrial gene. Based on the results of tree reconstructions and molecular dating, five major lineages are recognized: "tianschanica," "concolor," "caudata," "betulina," and "caucasica." It is established that the three latter lineages constitute a clade and that the long‐tailed birch mouse Sicista caudata is the sister group of the "caucasica" lineage. The "tianschanica" lineage is placed as the sister branch to all other species, however, with insufficient support. The cytochrome b tree is generally concordant with the nuclear topology. The molecular clock results suggest that the radiation among the main lineages occurred in the Late Miocene–Early Pliocene (6.0–4.7 Mya). The correspondence between molecular dating and the fossil record is discussed. Based on nuclear data, a high level of divergence between cryptic species in the "tianschanica" lineage is confirmed. Mitochondrial and nuclear data suggest the existence of a potential cryptic species within Sicista strandi. [ABSTRACT FROM AUTHOR]