Analysis of Macrozoobenthic Species Associations in the Eastern European Plain Under Changing Climatic Zone Conditions

ABSTRACT The assessment of the geographical distribution of species under the influence of environmental factors at different scales is important in ecological studies. This study aimed to investigate macrozoobenthos species associations and determine the factors influencing their co‐occurrence, based on data from various climatic zones of the Eastern European Plain. We analysed a large dataset from 11 mid‐sized and 81 small rivers in the Lower Volga Basin. Using a discrete binomial distribution, we identified pairs of associated species, grouped them and analysed their dependence on various abiotic factors. Four clusters of macrozoobenthic species were identified, gradually replacing each other from the forest‐steppe to the semi‐desert climatic zone. From high to low latitudes, in these clusters the number of rheophilic and freshwater species decreased, while the number of limnophilic, euryhaline and halophilic species increased. Species associations with habitat are determined by morphological and physiological adaptations to the complex of abiotic factors within local biotopes, trophic specialisation and facilitative interactions. The abiotic characteristics of the biotopes, in turn, were influenced by the following climatic and landscape factors: Average annual air temperature, precipitation volume influences salinity in the watercourses, and finally, the altitude and ruggedness of the terrain influenced water velocity. These factors constrained the spatial distribution of identified species assemblages to varying degrees. The results obtained contribute significantly to our understanding of the geographical distribution of macrozoobenthic assemblages. The methodical approach employed in this study has the potential to facilitate the distribution analysis of other groups of living organisms across diverse spatial scales.