Species diversity consists of three components: species richness,taxonomic or phylogenetic diversity and species evenness. Species richness is a simple count of species,taxonomic or phylogenetic diversity is the genetic relationship between different groups of species,whereas species evenness quantifies how equal the abundances of the species are. Species diversity in a dataset can be calculated by first taking the weighted average of species proportional abundances diversity of microorganisms pdf the dataset, and then taking the inverse of this.
The denominator equals mean proportional species abundance in the dataset as calculated with the weighted generalized mean with exponent q – 1. The proportional abundances themselves are used as weights.
The value of q defines which kind of mean is used. 2 corresponds to the arithmetic mean. In practice, q modifies species weighting, such that increasing q increases the weight given to the most abundant species, and fewer equally abundant species are hence needed to reach mean proportional abundance.
Consequently, large values of q lead to smaller species diversity than small values of q for the same dataset. If all species are equally abundant in the dataset, changing the value of q has no effect, but species diversity at any value of q equals species richness. In many real datasets, the least abundant species is represented by a single individual, and then the effective number of species would equal the number of individuals in the dataset.