Diversity can calculate several common diversity and evenness metrics. These metrics can be calculated for a single collection by clicking the calculate metrics button. They can also be calculated for all collections in one step by going to the Collections menu and choosing Calculate Metrics for All Collections.
If you want to see the effect on the metrics of removing some species from a collection, just uncheck those species next to their names and click calculate metrics again.
The metrics can be exported to a comma-delimited text file by going to the File menu and choosing Export Ecological Metrics.
Richness is the total number of species in a collection. It is symbolized by S.
Sample size is the total number of individuals in a collection. It is symbolized by N.
Shannon’s H is an entropy metric that reflects both richness and evenness. It is calculated as:
where pi is the proportion of the total number of individuals represented by that species (calculated as the number of individuals of one species divided by the total number of individuals of all species in that collection).
Buzas-Gibson E is an evenness metric that relates Shannon's H to species richness. It is calculated this way:
Pielou’s J is an evenness metric like Buzas-Gibson E in that it reflects both richness and evenness, but is calculated by dividing by the log of richness rather than richness:
Peter’ Ess is an evenness metric based on the concept of variance in the proportions of species. It is calculated as:
Hurlbert’s PIE is an evenness metric based on the probability that two successive individuals taken from a collection belong to the same species. It is calculated as:
Simpson’s D is similar in concept to Hurlbert's PIE, but reflects the probability that two successive individuals will belong to different species. Simpson’s D is calculated as:
The fraction in front of the sum is a bias correction for sample size.
The Chao-1 metric is unlike any of the other metrics in that it is an extrapolation estimate of the total diversity in a collection. It extrapolates diversity by adding an estimate of the unsampled diversity given by the number of species that occur only once in a collection (s1) and the number of species that occur only twice in a collection (s2). It is calculated as: