bipartite (version 0.7)

togetherness: Calculates the number of identical co-presences and co-absences for species-on-islands

Description

Togetherness, or T-score, describes the level of similarity in the distributional pattern of two species. Originally proposed by Stone & Roberts (1992) for biogeographical situations can it also be applied e.g.~to pollinators on different host plants.

Usage

togetherness(web, normalise=TRUE, FUN = mean, ...)

Arguments

web

A matrix with binary or counted interactions/links, where the higher trophic level is represented by columns.

normalise

Logical; shall index be normalised to a range of 0-1?

FUN

The function to summarise species-pair T-scores with; defaults to mean.

...

Arguments passed on to FUN, especially na.rm=T or colours for hist.

Value

• Returns the average (default) togetherness of all species combinations.

References

Stone, L. and Roberts, A. 1992 Competitive exclusion, or species aggregation? An aid in deciding. Oecologia 91, 419--424

See Also

C.score for another of Stone & Roberts' indices.

Examples

(m <- matrix(c(0,1,0,0,1,1,0,1,1,0), ncol=2, byrow=TRUE))
togetherness(m)
# or, with two togethernesses:
(n <- matrix(c(0,1,1,0,1,1,0,0,1,1,0,1,0,1), ncol=2, byrow=TRUE))
togetherness(n, normalise=FALSE)

data(Safariland)
togetherness(m)