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On the basis of a study of our own and published data on voles from the shores of Lake Evoron (n = 8) and the Amgun River (n = 8) in the Evoron-Chukchagir lowland, as well as individuals from laboratory breeding, new data on karyotypic variation (2n = 38–41, NF = 54–59), chromosomal transformations, and their combinations in the karyotype are presented. The numbering of chromosomes in the Evoron vole karyotype using differential (GTG) staining methods made it possible to identify pairs of chromosomes involved in various chromosomal rearrangements and to number the original pairs for the pairs formed from them by chromosome fusion. The tandem telomere-telomere (TTel) fusions of biarmed chromosomes form a large submetacentric element Mev1/4M; telomere-centromere fusion (TCen) as a result of inactivation of the centromere in one of the acrocentric pairs forms either an acrocentric (Mev17/18A) or metacentric element (Mev17/18M), and the Robertsonian translocation of the same pairs forms a metacentric element (Mev17/18M). The variability of the centromere position in two pairs of autosomes (Mev8 and Mev14) is also shown. The revealed rearrangements made it possible to describe twelve variants of the karyotype: two with 2n = 41, six with 2n = 40, three with 2n = 39, and one with 2n = 38. It is proposed that the voles of the Evoron-Chukchagir lowland be assigned to the “еvoron” chromosome race, and the other voles be assigned to the “argi” race. Prolific offspring from the individuals with TTel fusion in the karyotype and a high percentage of this rearrangement in individuals from natural sample sets indicates the absence of a harmful effect on the viability of voles.

The ranges of all three zokor (Myospalax) species, the little-studied burrowing rodent, are described in southeastern Transbaikalia, Russia, based on the results of special expeditions. Myospalax aspalax inhabits only the Onon River basin, M. psilurus populates the forested steppe in the Argun River basin and the upper reaches of the Borzya River (a tributary of the Onon River), while M. armandii is known only from the Klichkinskii Mountain Range. The distribution area of M. armandii is very small (less than 2000 km2) and is isolated from the other parts of the range (in China). The zokor species in the region are shown to be parapatric, with no sympatry being involved. The ranges of M. psilurus and M. armandii are the closest, the distance between the closest settlements being less than 5 km. Reduction in the zokor distributions is observed in Transbaikalia. It is advisable to include M. armandii on the Red Data list of Russia.

Microsatellite analysis was used to examine intraspecific polymorphism in two extensive continental isolates of the striped field mouse (Apodemus agrarius Pallas, 1771) separated by the Baikal disjunction. Striped field mice from the western isolate (from the European and Kazakh-Siberian parts of the range) and from the eastern isolate (from the territory of the Middle Amur Region and Coastal Territory of Far East) were tested. The analysis used 180 specimens collected from 33 localities and five microsatellite loci developed earlier for the genus Apodemus. The work was carried out based on the summation of local samples in each of the aforementioned geographical regions. It was shown that allelic diversity and the number of specific alleles were higher in the eastern isolate that may be the result of the longer habitation of the striped field mouse in the eastern part of the range. The limited number of specific alleles in the western isolate as compared to the eastern one can be determined by the founder effect and may reflect the direction of the historical migration of the species from east to west. Our results demonstrate no more than a population level of differentiation within the continental isolates of the striped field mouse and indicate no more than a subspecies level of differences between these isolated forms, i.e., the relatively recent penetration of A. agrarius to western Eurasia.

Morphological (craniometrical characteristics and variations of cusp t3 on the second upper molar (M2)) and genetic (polymorphism of chromosomes and blood proteins) variability was analyzed in small island populations of the striped field mouse Apodemus agrarius Pallas, 1771 from the Peter the Great Bay (Sea of Japan). It was found that the absence of t3 on M2 is not a specific trait for A. agrarius. It was demonstrated that the population of field mice on the Bolshoy Pelis Island significantly differs from the populations from other islands and from the mainland according to the craniometrical parameters, teeth phenes, and variants of blood transferrin. The possible age of establishment of the island populations of the striped field mouse is discussed.

International audience; To better understand the evolutionary history of oriental wildlife newcomers in Europe, we studied the phylogeography and demographic history of the striped field mouse, Apodemus agrarius, throughout its Palaearctic distribution area. Genetic datasets including cytochrome b gene sequences and microsatellite markers were analysed using a large range of population genetics methodologies, including coalescent models and approximate Bayesian computations. Our results showed high mitochondrial genetic homogeneity among A. agrarius populations throughout the Palaearctic region, but microsatellite markers detected a finer population structure with the genetic differentiation of populations from the Eastern and Western distribution ranges. The Western colonisation likely originated from Far East Russian populations during one of the last interglacials. After their colonisation of the Central Asia and Western regions, the Central Palaearctic populations became isolated from their Eastern relatives. Our coalescent-based approaches suggested a separation between these two distribution ranges around 38 kya or more recently (around 11 kya). Limited gene flow still happened between populations in the two main distribution ranges, mainly from the Eastern to Western populations. Our study, for the first time, provides an overview of the evolutionary and demographic history of the striped field mouse throughout the Palaearctic region. A. agrarius appears to be an Asiatic immigrant and a relatively new member of the European fauna community. This study further confirms the important role of Far East Asian regions as a source of European biodiversity.

We examine the diversity of six microsatellite loci and partial RAG1 exon of “barabensis” and “pseudogriseus” karyoforms in Cricetulus barabensis sensu lato species complex. A total of 435 specimens from 68 localities ranging from Altai to the Far East are investigated. The results of the population structure analysis (factor analysis and NJ tree based on Nei genetic distances) support subdivision into two well-differentiated clusters corresponding to the two karyoforms. These karyoforms are also well differentiated by the level of microsatellite variability. In several “barabensis” specimens, we found microsatellite alleles that are common in “pseudogriseus” populations but are otherwise absent in “barabensis.” Most of these specimens originate from a single population in one of the zones of potential contact between karyoforms, Kharkhorin in Central Mongolia. These molecular results are consistent with previously published karyological data in suggesting that rare hybridization events between the two chromosomal races occur in nature.

The striped field mouse Apodemus agrarius is an invasive species new for Magadan oblast; however, the adaptation of the animals to the conditions of the habitats north of the Sea of Okhotsk has been successful. The full nucleotide sequence of the cytochrome b (cytb) gene from the mtDNA has been determined for mice from four local populations in the region (settlements of Snezhnaya Dolina, Snezhnyi, Solnechnyi, and Talon), and five cytb-haplotypes have been detected. Phylogenetic analysis revealed the similarity of cytb nucleotide sequences in the mice from the habitats north of the Sea of Okhotsk and the conspecifics from the Far East-Chinese part of the range. The invasion of A. agrarius into Talon is likely to have started from Primorsky krai, whereas the animals captured in Snezhnaya Dolina had ancestors from both Primorsky krai and from China, and the animals captured in Snezhnyi and Solnechnyi were exclusively of Chinese ancestry. The striped field mice from Snezhnyi and Solnechnyi were of a single monophyletic origin. The origin of mice captured in Snezhnaya Dolina was apparently polyphyletic, and the origin of the animals from Talon was monophyletic and different from the origin of other populations of the enclave located north of the Sea of Okhotsk. Investigation of 16 allozyme loci revealed highly significant differences between the samples of striped field mice of Snezhnyi, Solnechnyi, and Talon. The variability parameters in the set of biochemical gene markers used for the analysis showed a trend to a decrease in striped field mouse samples from the habitats north of the Sea of Okhotsk. Genetic analysis revealed that the local settlements of A. agrarius in Magadan oblast are currently represented by small isolated populations.

The phylogeography of four Apodemus species (Apodemus agrarius, Apodemus peninsulae, Apodemus latronum, and Apodemus draco) was studied in the Far East of Asia, based on sequences of the mitochondrial DNA cytochrome b gene. The results obtained show the existence of many different genetic lineages within the studied Apodemus species, suggesting the isolation and differentiation of populations in multiple refuge areas. Higher genetic diversities in some regions such as Yunnan, Sichuan (China), and eastern Russia suggest these areas are potential refuges for these species. The existence of such complex genetic structures could be linked to the presence of many biogeographic barriers (Himalaya Mountains, Tien-shan Mountains, Altai Mountains, Tibetan Plateau, Gobi desert, Yunnan Guizhou Plateau, Dzungaria basin, and others) in these regions, which were probably reinforced during the Quaternary climate changes. These barriers also played an important role concerning the low dispersal abilities of the two studied Apodemus species adapted to forest habitats (A. latronum and A. draco) with respect to colonizing regions other than China. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 797-821.