Interspecies hybridization and factors of its formation in the East-European mammalian fauna

Phenomenon of hybridization as a special type of interspecies relationships is considered in relation to mammalians of East-European fauna. Hybridization can be considered either as restoration of panmixia or as violation of isolation depending on the level of evolutionary differentiation of populations. Diversity of hybridization cases could be categorized in six main groups, analyzed separately. It is shown that principal aspect in the concept of hybridization is the presence of «trigger» mechanisms of this process. In case of experimental (incl. stock-raising) hybridization, the key factor is an artificial formation of reproductive pairs. In natural conditions, main factor provoking hybridization is the changing of species geographical ranges. The leading role in case of young species is played by the expansions of allospecies inside geographical ranges of their siblings. Territory of Eastern Europe is a zone of high concentration of cryptic biodiversity, as well as polygon for multipling expansions. The expansions associated with colonization of post-glacial zones (in the past) and agricultural landscapes (recently), and with similarly directed migrations of fauna are the result of global climate changes. Keywords: hybridization, interspecies relations, invasions, evolution.