Variability indexes of a taxonomic diversity of macrozoobentos communities on the longitudinal gradient of the rivers

Indexes of the taxonomic diversity, based on Rао's quadratic entropy, are discussed. On an example of macrobenthos communities of the average flat river Sok (inflow of the Saratov water basin) the matrix of taxonomic distances between 277 species of macrozoobenthos on the basis of 11 levels of a hierarchical tree of Linnaean classification system is generated. The dynamics of variability of indexes of taxonomic diversity ∆ and distinctness ∆+ is considered on a longitudinal profile of a waterway. Monotonous growth of indexes on a natural gradient from a river source to its mouth which is possible to consider as the law of a river continuum caused by nestedness effect of compositions of species is shown. The comparative analysis of sensitivity of the indexes and estimate of confidence intervals are made.