THE FAUNA OF CADDISFLIES (TRICHOPTERA: INSECTA) OF THE ULBA RIVER BASIN (SOUTH-WESTERN ALTAI)

Abstract

The rivers of South-West Altai are poorly-studied by entomologists. To analyze the fauna composition and spatial distribution of caddisflies in watercourses of the Ulba river basin (South-Western Altai), the hydrobiological studies in 11 streams of the basin were performed in 2002-2013. The river basin is distinguished by high species richness of caddisflies. Here, 64 species of caddisflies from 38 genera and 19 families that is 48% of the species and 67% of the genera found in Kazakhstan are present. In the Ulba caddisflies fauna, the Transpalaearctic species (41%) dominate, a large quantity (33%) falls on Western Palaearctic ones. East Palaearctic species form 20% of the fauna, while the Altai and Siberia species – 6%. It is shown that despite the prevalence of widely distributed Transpalaearctic elements, the caddisflies fauna of South-Western Altai is hardly similar to that of the Altai-Sayan Mountain Country. Geographically approximate regions of Altai show the best similarity. The analysis of similarity of caddisflies species lists for some streams of South-Western Altai is evidence of a decisive role of abiotic factors of river biocenoses in the Trichoptera fauna formation. The suggestion has been made that ecological factors are critical in spatial distribution of caddisflies in the rivers of South-Western Altai. It is noted that composition and community structure of caddisflies depend on the level of anthropogenic transformation of rivers. The species richness of caddisflies and their share in total biomass of zoobenthos from river sites located below discharge points of polluted waters are reduced. The revealed features of caddisflies communities transformation in the impact zone call for modification of biotic indices used for assessing ecological state of rivers in the region.