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

Area of Science:

• Ecology
• Environmental Science
• Quantitative Biology

Background:

• Assessing species trait responses to environmental gradients necessitates integrating species distribution (L), environmental data (R), and species traits (Q).
• The fourth-corner and RLQ methods offer direct approaches to investigate trait-environment relationships by analyzing a cross-product matrix weighted by species abundances.

Purpose of the Study:

• To illustrate the complementary nature of the fourth-corner and RLQ methods.
• To demonstrate how combining these methods can advance ecological knowledge and improve the study of trait-environment interactions.

Main Methods:

• Analysis of three data tables: species distribution (L), environmental characteristics (R), and species traits (Q).
• Application of the fourth-corner method for testing individual trait-environment relationships.
• Utilization of the RLQ method for multivariate analysis and summarization of joint structures across the three tables.

Main Results:

• The fourth-corner method focuses on individual trait-environment associations.
• The RLQ method provides ordination scores to summarize the integrated structure of species traits, environmental variables, and species distributions.
• The study highlights the distinct yet complementary outputs of both methods when applied to ecological data.

Conclusions:

• The combined application of the fourth-corner and RLQ methods offers a more comprehensive understanding of trait-environment relationships than either method alone.
• Exploiting the complementarity of these techniques can lead to novel ecological insights and improved analytical power in ecological research.