cheddar (version 0.1-639)

TrophicSimilarity: Trophic similarity

Description

A measure of trophic overlap between nodes in a community.

Usage

TrophicSimilarity(community)
MeanMaximumTrophicSimilarity(community)

Value

TrophicSimilarity returns a matrix with NumberOfNodes rows and columns. MeanMaximumSimilarity returns a number.

Arguments

community

an object of class Community.

Author

Lawrence Hudson

Details

TrophicSimilarity computes `trophic similarity' (I) as defined by Martinez (1991). For each pair of nodes, I = c/(a+b+c), where a is the number of resources and consumers unique to one node, b is number of resources and consumers unique to the other node and c is the number of resources and consumers common to both nodes. Where two nodes have exactly the same set of resources and consumers, I = 1. Where two nodes have no resources or consumers in common, I = 0.

Williams and Martinez (2000) defined the mean maximum trophic similarity as the sum of the largest value in each column of I (excluding the diagonal), divided by the number of nodes.

References

Martinez, N. D. (1991) Ecological Monographs 61, 367--392.

Williams, R. J. and Martinez, N. D. (2000) Nature 404 180--182.

See Also

PredationMatrix, NumberOfNodes, TrophicSpecies

Examples

data(TL84)

I <- TrophicSimilarity(TL84)
I

MeanMaximumTrophicSimilarity(TL84)