[The role of the natural selection in supporting genotypical constancy of natural populations of Bradybaena fruticum (Muller), Mollusca, Gastropoda, as a result of ecological monitoring].

Prolonged 16-year's monitoring has revealed dynamics of genotypical structure in two generations of mollusks from eight natural populations of Bradybaena fruticum in four areas of Moscow region and two Moscow parks. The selection effect was determined through the analysis of shifts of allele frequencies, different age groups of the same generation and adults of different generations were compared. The selection effect on two polymorphous locuses--conchological and allozymic is revealed. It is shown, that the natural selection supports constancy of indicated polymorphous characters in populations in time. Two aspects of action of selection are revealed: the selection during life of one generation changes alleles' value; the direction of selection revealed among generations shows the advantage of geterozygotes. Vectors of selection in generations can differ. The mechanism of maintaining populational gomeostas in time is revealed. The supposition about primary importance of one of estherases alleles is confirmed.