Distance-based multivariate analyses confound location and dispersion effects
- Publication Type:
- Journal Article
- Citation:
- Methods in Ecology and Evolution, 2012, 3 (1), pp. 89 - 101
- Issue Date:
- 2012-02-01
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| Warton_et_al-2012-Methods_in_Ecology_and_Evolution.pdf | Published Version | 630.51 kB |
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A critical property of count data is its mean-variance relationship, yet this is rarely considered in multivariate analysis in ecology. This study considers what is being implicitly assumed about the mean-variance relationship in distance-based analyses - multivariate analyses based on a matrix of pairwise distances - and what the effect is of any misspecification of the mean-variance relationship. It is shown that distance-based analyses make implicit assumptions that are typically out-of-step with what is observed in real data, which has major consequences. Potential consequences of this mean-variance misspecification are: Confounding location and dispersion effects in ordinations; misleading results when trying to identify taxa in which an effect is expressed; failure to detect a multivariate effect unless it is expressed in high-variance taxa. Data transformation does not solve the problem. 6.A solution is to use generalised linear models and their recent multivariate generalisations, which is shown here to have desirable properties. © 2011 The Authors. Methods in Ecology and Evolution © 2011 British Ecological Society.
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