New data on the variability of quantitative and morphotypic parameters of B chromosomes (Bs) in the Korean field mouse Apodemus peninsulae from forest-steppe and forest biotopes of Zabaikalsky krai are presented. The karyotypes of these mice were found to contain 1–19 B chromosomes. All individuals had micro-B chromosomes, most often in combination with biarmed small and medium (but not large) Bs. Two geographic population groups were identified that were statistically significantly different in the number of Bs, indices of the mean number of Bs per individual (xB) and conditional “mass” of Bs (mB), as well as in the number of morphotypes and the frequency of micro-Bs. In the “northwestern” population group, relatively low values of quantitative Bs parameters are maintained. On the contrary, the “southeastern” group demonstrated high parameter values. The possible barrier role of the large Shilka and Onon rivers, as well as the steppe region in the middle and lower reaches of the Onon River, in maintaining numerical and morphotypic differences in B chromosomes between these groups is discussed. It was demonstrated that a decrease in the diversity of Bs morphotypes was most characteristic of the Korean field mice from forest-steppe biotopes, likely due to the location of these populations at the edge of their range and their existence in the most pessimal conditions for the species.
Рослик et al. (Wed,) studied this question.
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