LAUSR

To date a considerable amount of data on sympatric diversification of the laсustrine fish has been accumulated and many important advances made. However, the evolutionary mechanisms of the process still remain unclear. The paper discusses fish polymorphism in the water bodies of different latitudes, but the major focus is the question of sympatry in the charrs of the genus Salvelinus across the northern lakes. Numerous cases of diversification were comparatively analyzed, which provides evidence for the existence of several main pathways of evolutionary process. The pathways are controlled by environmental factors, which determine the structure of the lake ecosystems in the northern latitudes.