pianka: Pianka Niche Overlap Metric

In EcoSimR: Null Model Analysis for Ecological Data

Description

Takes a resource utilization matrix as input and returns the average pairwise Pianka's niche overlap index.

Usage

pianka(m = matrix(rpois(80, 1), nrow = 10))

Arguments

m	a matrix of resource utilization values.

Details

Pianka's niche overlap index is averaged over each unique species pair. The index is symmetric, with a normalization term in the denominator for the overlap between species 1 and 2. Values of Pianka's niche overlap index close to 0.0 reflect usage of exclusive resource categories, whereas values close to 1.0 reflect similar resource utilization spectra.

O_jk = O_kj = sum(p_ij*p_jk) / sqrt(sum((p_ij)^2)sum((p_jk)^2))

Value

Returns the average pairwise niche overlap.

Note

The resource utilization matrix (rows = species, columns = discrete resource categories) may include zeroes, but no negative numbers or missing values. Relative resource within a species is first calculated, so the rows need not sum to 1.0.

References

Pianka, E. 1973. The structure of lizard communities. Annual Review of Ecology and Systematics 4:53-74.

Winemiller, K.O. and E.R. Pianka. 1990. Organization in natural assemblages of desert lizards and tropical fishes. Ecological Monographs 60: 27-55.

See Also

czekanowski niche overlap index.

Examples

obsOverlap <- pianka(m=matrix(rpois(40,0.5),nrow=8))

Example output

Loading required package: MASS

EcoSimR documentation built on May 2, 2019, 7:26 a.m.