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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]

The systematics of the genus S icista is unclear, mostly because of the high level of chromosomal variability within the genus. One of the most challenging groups for systematists is the steppic S icista subtilis species group that extends from central Europe to Lake Baikal. We present a systematic review of these European southern birch mice using an integrative taxonomic approach., In this review, we evaluate the degree of genetic and morphological differentiation of the S icista subtilis complex by analysing 12 European populations, and propose a new taxonomic treatment for the subtilis group based on an integrative approach combining phylogenetic and morphometric analyses with a review on previously published cytogenetic and morphological data., The phylogenetic relationship was reconstructed using sequences of the whole mitochondrial cytochrome b ( CytB) and the nucleus-encoded interphotoreceptor binding protein ( IRBP) under the maximum parsimony and maximum likelihood criteria. Based on whole CytB sequences, genetic distances were reconstructed and visualised among the taxa. These data were supplemented with multivariate analysis of the morphology of the baculum and of the penile spike of museum specimens., Based on the genetic and the morphological data set, we suggest that the subspecies trizona and nordmanni should be raised to the species rank. We suggest S icista trizona ( Frivaldszky, 1865) and S icista nordmanni ( Keyserling and Blasius, 1840) as names for these species, respectively., The species status of S icista severtzovi is not supported by our results, so we recommend reclassifying it as a subspecies of S icista subtilis., Finally, the large genetic distance between the Hungarian and Romanian populations of S icista trizona led us to describe the Romanian population as a new subspecies. [ABSTRACT FROM AUTHOR]