The Importance of a Species in a Biocoenosis, a Class of Biocoenoses, and a Region: A Review of Combined Indexes

This paper reviews the combined indexes created to reflect the importance of a species (species population) in an individual biocoenosis, in a region (regional or spatial complex), and in a class (type) of biocoenoses. The main features of the indexes, such as the parameters included, structures of formulas, areas of applicability, and limitations of use are discussed. The content of some parameters, such as the frequency in a biocoenosis, the frequency in a region, and the presence, is made more accurate for an interdisciplinary context. The combined importance indexes were created from parameters that can be measured during the collection of mass data using common field research methods. The ease of measurement largely determines whether the combined indexes are in demand. The main areas of their application are in investigation of the dominance structure, in comparative analysis of importance values of different species in one biocoenosis, and in comparative analysis of biocoenoses considering the importance value of their constituent species. Therefore, combined indexes are used for the study of dynamics, for the description of classes of biocoenoses, for analysis of spatial series of biocoenoses, for calculation of the correlation between species or biocoenoses and the environment, for estimation of the biomass, for modeling of the geographical distribution of species, etc. Additionally, these indexes can be used everywhere where not only the composition but also the importance of species are considered. For example, currently a tendency to use combined indexes in geographic information systems has been outlined.