Bashinsky I. V. RussiaMoscowA. N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, 33 Leninsky Prospect, Moscow 119071, Russiaosipovv@mail.ru Author's articles ON THE CASTOR FIBER (CASTORIDAE, MAMMALIA) ACTIVITY INFLUENCE ON THE ECOSYSTEM BIODIVERSITY OF SMALL RIVERS IN THE FOREST-STEPPE ZONE