This work is dedicated to subfamily Murinae, which remains an area of relative taxonomic uncertainty, even within the Palearctic. Special attention is paid to Mus and Apodemus s. l., where the number of species within these genera has increased from 12 to 26 over the past 40 years. However, questions about the delimitation of a number of species and, accordingly, how many species exist in general, remain insufficiently clarified. The reasons lie in the ambiguity of species divergence, and therefore the solution to the problem is connected with the application of the system concept of the species, where according to modern interpretation the species can be a system of subordinate categories (semispecies, allospecies, species). A promising region for murine research is Southeast Asia, which is considered one of the key areas of formation and distribution of Mus and Sylvaemus representatives. Accumulated material for a series of DNA markers in this taxonomic group allows for comparative studies focusing on important aspects of molecular evolution. This concerns such a phenomenon as transition bias and its evolutionary compensation, because the ambiguous nature of nucleotide substitutions at different stages of divergence is an evidence of the irreducibility of evolution at different stages of historical development and raises questions about the correctness of using molecular data in phylogenetics. These aspects serve as a basis for conducting research, which purpose is to determine levels of evolutionary and genetic divergence and patterns of molecular evolution of Palearctic representatives of the Murinae subfamily, with an emphasis on Apodemus and Mus genera.
The scientific novelty of the study lies in objectivity of six degrees of evolutionary divergence, which includes: population, subspecies, allospecies, species, subgeneric, generic levels. The material for the study consists of six DNA markers: cytochrome b, D-loop, COI, 12S RNA, ISBP and Fv1, obtained from GenBank, as well as private samples for cytb and D-loop of mice from Israeli Mus and Apodemus.
The taxonomy and evolutionary scenario based on genetic differentiation was established primarily by the analysis of cytb gene, the results were confirmed by analysis of five more DNA markers. The effectiveness of the application of the systematic species concept to Palearctic mice, taking into account the presence of two categories of critic forms of semispecies and allospecies, has been proven. Within a number of genera and subgenera certain species and superspecies were identified, which should be recognized as separate; additionally, groups of allospecies have been distinguished. Taxonomy of the genus remains ambiguous, which is caused not only by different scales of differentiation of Western and Eastern Palearctic phyla, but also by the lack of information on key genus-specific features. As a result, within Apodemus s. l. group three taxonomic scenarios are possible; the system of Palearctic representatives of Mus subgenus is also complex and includes three taxonomic levels.
Modeling of the ecological niche of the forest mouse S. (superspecies sylvaticus) showed that the abiotic conditions of Western Europe, where the main cores of the range are concentrated, are the most favorable for the species. The main limiting factor for the spread of the species in the eastern direction is the continentality of the climate, which has an indirect effect through the types of vegetation on the location of the eastern limit of the range of S. (superspecies) sylvaticus and both subspecies, despite the peculiarities of their relatively independent origin.
A comparative analysis of the rates of molecular evolution, transition bias and its evolutionary compensation was carried out using six markers. According to the levels of variability, the nature of nucleotide substitutions is manifested. A comparative analysis of the features of the transition/transversion bias of nucleotide sequences in cytb gene in microbats (Vespertilionidae, Chiroptera) and mice (Muridae, Rodentia) shows a sharp predominance of transitions over transversions at the early stages of the evolutionary process, followed by equalization of ts/tv bias at the species and genus levels of divergences.
By example of 15 orders of Palearctic mammals it has been confirmed that the genetic differentiation of small and large mammalian taxa shifts to one taxonomic level, besides, the period of hidden speciation of micromammals (semi-/allospecies level) corresponds to divergence of standard macromammalian species, and all families have a transition bias and its evolutionary compensation. The degree of transition/transversion bias and, accordingly, the rates of its evolutionary compensation are ambiguous for long- and short-cycle species, which indicates a different nature of mutational processes in groups of mammals that differ in intensity of metabolism.
