Pianka Niche Overlap Metric

Usage

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

Arguments

m
a matrix of resource utilization values.

Value

Returns the average pairwise niche overlap.

Description

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

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))

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.

Examples

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

See also

czekanowski niche overlap index.