On the criteria for identifying rare species of algae and the analysis of taxonomic lists in sozological studies

The results of the analysis of data on rarely observed algal species on the territory of the Middle Volga Integrated Biosphere Reserve, based on the results of long-term observations are presented. In terms of frequency of occurrence, the number of singly recorded in general includes 286 species and intraspecific taxa, which is about a third of the total number of species of algal flora of the studied reservoirs and watercourses. Analysis of this list, taking into account data on the ecology of species and their distribution in water bodies of adjacent territories, made it possible to identify 133 taxa that need to be studied for their conservation status. The composition of species with a low frequency of occurrence is critically examined. New habitats of species included in the “Red Book of the Samara Region” have been identified. It is shown that the discovery of habitats of rare taxa and the presence of a large number of singly noted species require the collection and careful analysis of information on their occurrence based on the study of all hydrological and hydrochemical types of water bodies in the territory where sozological studies are carried out.