V.ratio: Calculates the variance-ratio as suggested by Schluter (1984)

Description Usage Arguments Details Value Note Author(s) References See Also Examples

View source: R/V.ratio.R


A of species association is provided by the ratio of the variance in total species number (or total density of individuals) in samples to the sum of the variances of the individual species.





A matrix with pollinators in columns and plants in rows. For biogeographical applications: rows are islands (or sites).


This is a rather straight-forward index, which is described and evaluated extensively in Schluter (1984). He also warns against overinterpretation of the value. In principle, V-ratios larger than 1 indicate positive, smaller than 1 negative associations. Ecologically, competition can lead to small or large values, depending on their exact effects (see discussion in the Schluter paper).


Returns the V-ratio, i.e. a single value representing the ratio of variance in species number and variance in individual numbers within species.


Any quantitative matrix is first transformed into a binary (presence-absence) matrix!

Do not interpret without first reading the paper! It's worth it! See also applications in other studies, such as Gotelli and Rohde (2002).


Carsten F. Dormann


Gotelli, N.J. and Rohde, K. (2002) Co-occurrence of ectoparasites of marine fishes: a null model analysis. Ecology Letters 5, 86–94

Schluter, D. (1984) A variance test for detecting species associations, with some example applications. Ecology 65, 998–1005

See Also

C.score for another measure of species associations.



Example output

Loading required package: vegan
Loading required package: permute
Loading required package: lattice
This is vegan 2.4-3
Loading required package: sna
Loading required package: statnet.common
Loading required package: network
network: Classes for Relational Data
Version 1.13.0 created on 2015-08-31.
copyright (c) 2005, Carter T. Butts, University of California-Irvine
                    Mark S. Handcock, University of California -- Los Angeles
                    David R. Hunter, Penn State University
                    Martina Morris, University of Washington
                    Skye Bender-deMoll, University of Washington
 For citation information, type citation("network").
 Type help("network-package") to get started.

sna: Tools for Social Network Analysis
Version 2.4 created on 2016-07-23.
copyright (c) 2005, Carter T. Butts, University of California-Irvine
 For citation information, type citation("sna").
 Type help(package="sna") to get started.

 This is bipartite 2.08
 For latest changes see versionlog in  ?"bipartite-package".
 For citation see: citation("bipartite").
 Have a nice time plotting and analysing two-mode networks.

Attaching package: 'bipartite'

The following object is masked from 'package:vegan':


[1] 0.5806452

bipartite documentation built on May 22, 2019, 1:02 a.m.