[Whitefish: a new mechanism of reproductive isolation]

Taxonoprint (a modification of DNA restrictase analysis) allows to distinguish sympatric species, that do not mate or produce hybrid offspring that are sterile or not viable. It is shown that taxonoprints of whitefish are very similar of identical. Sympatric whitefish are continuing to be separate despite they easily mate in experiments and in nature (up to 30% of individuals in nature are hybrids) and hybrids offspring have some features of heterosis. However it appears that hybrids of the second generation are not viable and can exist only because of back crossing with parents. In allows to keep a species independence in the process of gene exchange and to use heterosis of the first generation. Similar isolation mechanism is determined for other fish families (Acipensepidae, Clupeidae, Cyprinidae, Percidae) and some mammals (camels, sheep, bulls).