Abstract. In the present work chromosomal polymorphism is studied on the basis or cariotypes analisis of more than 100 species and intraspecific forms of Mammalia of the Caucasus. Divergence of branches on the phylogenetic trees received on different chromosomal reorganization is ambiguous, that is probably the consentience of recent and fast separation from the basic trunk of some groups. It is noticed for the first time that the morphological evolution was not always accompanied by visible chromosomal reorganization and the contrary. The obtained data testifies in favour of chromosomal formation of species in some genera: Talpa, Sicista, Pitymys, Microtus etc.

Introduction. Studying of chromosomal polymorphism and the role of chromosomal rearrangement in the formation of reproductive isolation is important in evolutionary researches. Robertson type chromosomal rearrangements, redistribution of heterochromatic material and chromosome division have dominating role in the evolution of karyotype.

Methods. During carrying the experimentation out, all landscape areas of the Caucasus were explored; karyological researches were carried out in 243 spots. We succeeded to study chromosomal complement of 100 species, forms and hybrids of the region. Chromosome preparations are received using a method of “dried out” preparations (Ford, Hamerton, 1956; Orlov, Bulatova, 1983).

Results. Karyological peculiarities conditioned by various distribution of structural heterochromatin prevail in Erinaceus. Karyotype evolution of moles in the Caucasus went by the way of chromosome division. Karyotype evolution of Pitymys in the Caucasus progressed step-by-step. Preglacial period probably was the longest and is characterized by the genesis of three independent species: P. schekovnikovi (2n = 54, NF = 62), P. majori (2n = 54, NF = 60) and P. daghestanicus (2n = 54, NF = 58). Chromosome evolution in the group “schekovnikovi” resulted from the pericentric inversion of four pairs of autosomes. In the chromosome set of P. majori the centromere position in two large autosome pairs changed, and that led to increasing of chromosome arm quantity to 60. As a result of pericentric inversion of the smallest acrocentric pair of P. daghestanicus a pair of metacentrics was formed, which is the marker chromosome of all the representatives of the group P. daghestanicus, and this led to increasing of chromosome arm quantity in set to 58.

Conclusion. Interaction of plain and mountain landscapes exerts essential influence on the karyotype evolution both in altitude and horizontal directions. Certain law was revealed: species with stable morphological parameter and sibling species possess polymorphous karyotype, and, on the contrary, species, which exophenes are subjected to the marked changeability, have stable karyotype long the whole length of the area. Almost all the types of chromosomal rearrangements known by this time are present in mammals of the Caucasus.