This study reports for the first time the banding pattern on chromosomes of the Tatra vole, Microtus tatricus, as revealed by G-, C-, and Ag-NOR staining procedures. The banded karyotype of M. tatricus was compared with Microtus (Terricola) subterraneus, M. (Stenocranius) gregalis, and M. (Blanfordimys) aghanus. The karyotype of M. tatricus possesses highly derived features, e.g., the low diploid number of chromosomes or unique combinations of arms in the biarmed autosomes. It is almost impossible to find clear relationships of M. tatricus with other extant vole species from the point of view of comparative karyology. The karyotypic changes in voles are apparently not accompanied by adequate divergence in morphological and genetic traits.
Geographic isolation of small populations in refugia during late Pleistocene glaciations resulted in population differentiation that in some cases lead to speciation. We report the karyotype of Microtus bavaricus, an evolutionary young and threatened rodent endemic to the Alps. Our results show that the karyotype of M. bavaricus is almost identical to that of M. liechtensteini (2N = 46, NF = 54). A close relationship between the two species was also supported by phylogenetic analysis of complete mitochondrial DNA sequences for the cytochrome b gene. The cytochrome b divergence between Microtus bavaricus and M. liechtensteini was 1.7 %, the lowest estimate observed among the 14 currently recognised species of Eurasian pine voles (subgenus Terricola).