Definitions: S, observed species richness; \(p_{i}\), relative abundance of species i; q , exponent that determines the sensitivity to rare species (0 = very sensitive, 2 = not very sensitive); N, observed number of individuals in the sample; \(X_{i}\) number of individuals of species i; ENS, the effective number of species which is the number of equally abundant species that results in the same value of diversity as the sample. To calculate \(E_{n}\), equation 3 can be solved numerically for given values of \(S_{n}\)and n.