Estimation of the Zonal Distribution of Species of Bottom Communities in Lowland Rivers of the Middle and Lower Volga River Basin

Abstract—A comparative analysis of the variability of the species structure of macrozoobenthos communities in small and medium rivers of the Middle and Lower Volga river basin has been carried out. The statistically significant influence of the natural climatic zone, where the watercourse is located, and manifestation of the latitudinal gradient of biodiversity are shown. A list of indicator species has been made for each geographical zone identified using different criteria of biotopical distribution. Based on the analysis, the indicator value (IndVal) index, which takes into account the zonal distribution of both the occurrence frequencies of a species and its abundance ratios, was recognized as the most adequate. Association rules that contain combinations of species that most frequently occur together in hydrobiological tests have been formulated using the Apriory algorithm.