<P> The same equation can be used to calculate the diversity in relation to any classification, not only species . If the individuals are classified into genera or functional types, p i (\ displaystyle p_ (i)) represents the proportional abundance of the ith genus or functional type, and D equals genus diversity or functional type diversity, respectively . </P> <P> Often researchers have used the values given by one or more diversity indices to quantify species diversity . Such indices include species richness, the Shannon index, the Simpson index, and the complement of the Simpson index (also known as the Gini - Simpson index). </P> <P> When interpreted in ecological terms, each one of these indices corresponds to a different thing, and their values are therefore not directly comparable . Species richness quantifies the actual rather than effective number of species . The Shannon index equals log (D), and in practice quantifies the uncertainty in the species identity of an individual that is taken at random from the dataset . The Simpson index equals 1 / D and quantifies the probability that two individuals taken at random from the dataset (with replacement of the first individual before taking the second) represent the same species . The Gini - Simpson index equals 1 - 1 / D and quantifies the probability that the two randomly taken individuals represent different species . </P> <P> Depending on the purposes of quantifying species diversity, the dataset used for the calculations can be obtained in different ways . Although species diversity can be calculated for any dataset where individuals have been identified to species, meaningful ecological interpretations require that the dataset is appropriate for the questions at hand . In practice, the interest is usually in the species diversity of areas so large that not all individuals in them can be observed and identified to species, but a sample of the relevant individuals has to be obtained . Extrapolation from the sample to the underlying population of interest is not straightforward, because the species diversity of the available sample generally gives an underestimation of the species diversity in the entire population . Applying different sampling methods will lead to different sets of individuals being observed for the same area of interest, and the species diversity of each set may be different . When a new individual is added to a dataset, it may introduce a species that was not yet represented . How much this increases species diversity depends on the value of q: when q = 0, each new actual species causes species diversity to increase by one effective species, but when q is large, adding a rare species to a dataset has little effect on its species diversity . </P>

What are the two specific concerns of species diversity species diversity is concerned with both and