Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 544500
Title Integrating spatial and phylogenetic information in the fourth-corner analysis to test trait–environment relationships
Author(s) Braga, João; Braak, Cajo J.F. ter; Thuiller, Wilfried; Dray, Stéphane
Source Ecology 99 (2018)12. - ISSN 0012-9658 - p. 2667 - 26764.
DOI https://doi.org/10.1002/ecy.2530
Department(s) PE&RC
Biometris
Publication type Refereed Article in a scientific journal
Publication year 2018
Keyword(s) community ecology - fourth-corner analysis - functional ecology - Moran's spectral randomization - null models - type I error
Abstract

The fourth-corner analysis aims to quantify and test for relationships between species traits and site-specific environmental variables, mediated by site-specific species abundances. Since there is no common unit of observation, the significance of the relationships is tested using a double permutation procedure (site based and species based). This method implies that all species and sites are independent of each other. However, this fundamental hypothesis might be flawed because of phylogenetic relatedness between species and spatial autocorrelation in the environmental data. Here, using a simulation-based experiment, we demonstrate how the presence of spatial and phylogenetic autocorrelations can, in some circumstances, lead to inflated type I error rates, suggesting that significant associations can be misidentified. As an alternative, we propose a new randomization approach designed to avoid this issue, based on Moran's spectral randomization. In this approach, standard permutations are replaced by constrained randomizations so that the distribution of the statistic under the null hypothesis is built with additional constraints to preserve the phylogenetic and spatial structures of the observed data. The inclusion of this new randomization approach provides total control over type I error rates and should be used in real studies where spatial and phylogenetic autocorrelations often occur.

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