Species Diversity Index - allows to assess the structure of a community by comparing the characteristics of its constituent species.

The ratio between the number of species and an indicator of significance: abundance, biomass, productivity, etc. The most commonly used are the Gleason Species Diversity Index (ratio of the total number of species to the logarithm of the number of individuals), Simpson (ratio of the total number of species to the number of individuals of a species), Shannon-Weaver (determined by the formula H=- Spi ln pi, where i=1,2...S; S - number of species; pi - relative abundance of the i-th species) and McIntosh.