Functional diversity in marine fish assemblages

Abstract

In the last decades, the rising interest in trait-based ecology is closely related to a growing demand for knowledge on ecosystems’ functioning and on mechanisms generating ecological patterns and processes, and with the urgency for approaches that allow to predict the consequences of climate change and anthropogenic impacts (McGill et al., 2006; De Bello et al., 2021a,b). This fundamental knowledge is difficult to obtain when considering specific species (i.e., taxonomic-based ecology), therefore ecologists are increasingly using functional diversity approaches (i.e., trait-based ecology), with the added advantage of allowing the comparison across different ecosystems and biogeographical regions, which due to biogeographical reasons support different species compositions (e.g., Henriques et al., 2017a,b). Functional diversity (FD) refers to the distribution and range of what species do (as determined by their functional traits) in a given ecosystem, influencing how the ecosystem operates or functions (e.g., stability, dynamics, productivity; Tilman, 2001; Petchey and Gaston, 2006). Currently, the most accepted definition of the trait was proposed by Violle and colleagues in which a trait is defined as “any morphological, physiological or phenological feature measurable at the individual level, from the cell to the whole organism” (Violle et al., 2007). For a trait to be considered a functional trait, it needs to influence organismal performance (fitness), meaning its growth, reproduction, and/or survival (McGill et al., 2006; Violle et al., 2007). Additionally, traits can also be related to the effect of organisms on ecosystem properties, or on the other hand, to how they respond to a disturbance or environmental change (Hooper et al., 2005). In this way, traits can be further divided into the following: (1) effect traits, those that significantly affect another trophic level (e.g., predator-prey interactions) and/or an ecosystem process (e.g., nutrient cycling, primary productivity), regardless of whether they affect or not the organismal performance; (2) response traits, those that allow organisms to survive, grow, and reproduce under different disturbances and/or environmental conditions (biotic and abiotic factors; Lavorel and Garnier, 2002).