Trait-based ecology: definitions, methods, and a conceptual framework

Abstract Functional diversity can be studied at different levels of organization of biological systems. Here the chapter considers the individual as a key level to understanding this functional diversity. Adaptation occurs at this level, and the functioning and responses of individuals determine those of populations, communities, and ecosystems. The ‘trait’ concept allows one to assess the different expressions of functions performed by organisms, and is extensively used in the various fields of study concerned with biological diversity. A trait is defined as ‘any morphological, physiological, or phenological heritable feature measurable at the level of the individual, from the cell to the whole organism, without reference to the environment or any other level of organization’. Trait-based ecology, the discipline at the core of this book, extensively uses the trait concept at different levels of organization. A conceptual ‘response and effect’ framework allows for the linkage of the response of plants to environmental factors with the potential effects of this on ecosystem properties and services. Environmental factors filter species as a function of their trait values (called ‘response traits’), resulting in a community functional structure defined on the basis of the distribution of trait values in this community. In turn, this functional structure has impacts on ecosystem properties and the services delivered by these to humans, through ‘effect traits’. The chapter argues that it is the components of the functional structure of communities which have impacts on ecosystem properties and services, and not the number of species present in these communities.