The traits of "trait ecologists": an analysis of the use of trait and functional trait terminology

Abstract

Trait and functional trait approaches have revolutionised ecology improving our understanding of community assembly, species coexistence, and biodiversity loss. Focusing on traits promotes comparability across spatial and organisational scales, but terms must be used consistently. While several papers have offered definitions, it remains unclear how ecologists operationalise ’trait’ and ’functional trait’ terms. Here we evaluate how researchers and the published literature use these terms and explore differences among subdisciplines and study systems (taxa and biome). By conducting both a survey and a literature review, we test the hypothesis that ecologists’ working definition of ‘trait’ is adapted or altered when confronting the realities of collecting, analysing and presenting data. From 486 survey responses and 712 reviewed papers, we identified inconsistencies in the understanding and use of terminology among researchers, but also limited inclusion of definitions within the published literature. Discrepancies were not explained by subdiscipline, system of study, or respondent characteristics, suggesting there could be an inconsistent understanding even among those working in related topics. Consistencies among survey responses included the use of morphological, phenological and physiological traits. Previous studies have called for unification of terminology, yet our study shows proposed definitions are not consistently used or accepted. Sources of disagreement include trait heritability, defining and interpreting function, and dealing with organisms in which individuals are not clearly recognisable. We discuss and offer guidelines for overcoming these disagreements. The diversity of life on Earth means traits can represent different features that can be measured and reported in different ways, and thus, narrow definitions that work for one system will fail in others. We recommend ecologists embrace the breadth of biodiversity using a simplified definition of ’trait’ more consistent with its common use. Trait-based approaches will be most powerful if we accept that traits are at least as diverse as trait ecologists.