Components of functional diversity revisited: A new classification and its theoretical and practical implications

Abstract

Functional diversity is regarded as a key concept for understanding the link between ecosystem function and biodiversity. The different and ecologically well‐defined aspects of the concept are reflected by the so‐called functional components, for example, functional richness and divergence. Many authors proposed that components be distinguished according to the multivariate technique on which they rely, but more recent studies suggest that several multivariate techniques, providing different functional representations (such as dendrograms and ordinations) of the community can in fact express the same functional component. Here, we review the relevant literature and find that (1) general ecological acceptance of the field is hampered by ambiguous terminology and (2) our understanding of the role of multivariate techniques in defining components is unclear. To address these issues, we provide new definitions for the three basic functional diversity components namely functional richness, functional divergence and functional regularity. In addition, we present a classification of presence‐/absence‐based approaches suitable for quantifying these components. We focus exclusively on the binary case for its relative simplicity. We find illogical, as well as logical but unused combinations of components and representations; and reveal that components can be quantified almost independently from the functional representation of the community. Finally, theoretical and practical implications of the new classification are discussed.

Relationships between functional alpha and beta diversities of flea parasites and their small mammalian hosts

“…It is now commonly recognized that functional alpha diversity is a multifaceted concept that can be characterized by a number of components, namely functional richness, functional divergence and functional regularity (Mason et al, 2005;Villéger et al, 2008;Tucker et al, 2017;Mammola et al, 2021;Schmera et al, 2023). Schmera et al (2023) proposed a concept of so-called functional diversity units (FDUs) which are discrete entities that represent community members (e.g. species) from a functional perspective.…”

“…It is now commonly recognized that functional alpha diversity is a multifaceted concept that can be characterized by a number of components, namely functional richness, functional divergence and functional regularity (Mason et al ., 2005 ; Villéger et al ., 2008 ; Tucker et al ., 2017 ; Mammola et al ., 2021 ; Schmera et al ., 2023 ). Schmera et al .…”

“…Schmera et al . ( 2023 ) proposed a concept of so-called functional diversity units (FDUs) which are discrete entities that represent community members (e.g. species) from a functional perspective.…”

“…how large is a community in relation to functional traits of its members), whereas functional divergence and functional regularity answer the question about how different and how variable, respectively, these FDUs are. The components of functional alpha diversity can be calculated based on the unrooted functional tree constructed from the matrix of trait (dis)similarity between species in a community (Cardoso et al ., 2022 ), where functional richness, functional divergence and functional regularity are represented by the sum, the mean and the variance of the branch lengths, respectively (Cardoso et al ., 2022 ; Schmera et al ., 2023 ). In the framework of this study, we considered these components of functional diversity separately.…”