asbio (version 0.2-1)

evenness: Pielou's measure of species evenness

Description

Calculates Pielou's measure of species evenness, i.e. J = H'/ln(S) where H' is Shannon Weiner diversity and S is the total number of species in a sample, across all samples in dataset.

Usage

evenness(x)

Arguments

x

A vector or matrix of species abundances (e.g. counts). The function assumes that species are in columns and sites are in rows.

Value

• Returns Pielou's J.

Details

Many diveristy indices incoporate evenness (e.g. Simpson's diversity, Shannon- Weiner diversity). Diversity indices which concentrate totally on evenness are fraught with problems including dependence on species counts (McCune and Grace 2002). A particular problem with Pielou's index is that it is a ratio of a relatively stable index, H', and one that is strongly dependent on sample size, S.

References

McCune, B., and Grace, J.B. (2002) Analysis of ecological communities. MjM Software design. Gelenden Beach OR.

See Also

SW.index, fidelity, const

Examples

library(vegan)
data(varespec)
evenness(varespec)