PiankaVariance Niche Overlap Metric

Usage

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

Arguments

m
a matrix of resource utilization values.

Value

Returns the variance of the average pairwise niche overlap.

Description

Takes a niche utilization matrix as in put and returns the variance of Pianka's niche overlap index.

Details

A large value for variance implies that some species pairs show high niche overlap and others show low niche overlap. A low value for variance implies that niche overlap (high or low) is very similar among all species pairs.

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

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

Examples

obsVar <- pianka_var(m=matrix(rpois(40,0.5),nrow=8))

See also

pianka niche overlap index.