Combining the fourth-corner and the RLQ methods for assessing trait responses to environmental variation

Ecology. 2014 Jan;95(1):14-21. doi: 10.1890/13-0196.1.

Abstract

Assessing trait responses to environmental gradients requires the simultaneous analysis of the information contained in three tables: L (species distribution across samples), R (environmental characteristics of samples), and Q (species traits). Among the available methods, the so-called fourth-corner and RLQ methods are two appealing alternatives that provide a direct way to test and estimate trait-nvironment relationships. Both methods are based on the analysis of the fourth-corner matrix, which crosses traits and environmental variables weighted by species abundances. However, they differ greatly in their outputs: RLQ is a multivariate technique that provides ordination scores to summarize the joint structure among the three tables, whereas the fourth-corner method mainly tests for individual trait-environment relationships (i.e., one trait and one environmental variable at a time). Here, we illustrate how the complementarity between these two methods can be exploited to promote new ecological knowledge and to improve the study of trait-environment relationships. After a short description of each method, we apply them to real ecological data to present their different outputs and provide hints about the gain resulting from their combined use.

MeSH terms

  • Adaptation, Physiological / physiology*
  • Altitude
  • Ecosystem*
  • Models, Biological*
  • Phytochemicals
  • Plants / classification*
  • Snow

Substances

  • Phytochemicals