Abstract
Understanding how the biodiversity of freshwater fish assemblages changes over time is an important challenge. Until recently most emphasis has been on taxonomic diversity, but it is now clear that measures of functional diversity (FD) can shed new light on the mechanisms that underpin this temporal change. Fish biologists use different currencies, such as numerical abundance and biomass, to measure the abundance of fish species. Nonetheless, because they are not necessarily equivalent, these alternative currencies have the potential to reveal different insights into trends of FD in natural assemblages. In this study, the authors asked how conclusions about temporal trends in FD are influenced by the way in which the abundance of species has been quantified. To do this, the authors computed two informative metrics, for each currency, for 16 freshwater fish assemblages in Trinidad's Northern Range that had been surveyed repeatedly over 5 years. The authors found that numerical abundance and biomass uncover different directional trends in these assemblages for each facet of FD, and as such inform hypotheses about the ways in which these systems are being restructured. On the basis of these results, the authors concluded that a combined approach, in which both currencies are used, contributes to our understanding of the ecological processes that are involved in biodiversity change in freshwater fish assemblages.
Highlights
Freshwater fishes are one of the most diverse vertebrate taxa (Magurran et al, 2011), and one of the most threatened because of multiple anthropogenic impacts including introductions of nonnative invasive species, modification and destruction of habitats and overexploitation (Albert et al, 2020; Dudgeon et al, 2006; Reid et al, 2019)
The authors focused on functional diversity (FD), a facet of biodiversity that is gaining increasing attention in the literature (Laureto et al, 2015; Villéger et al, 2017), and for this they used data from rivers in the Northern Range on the island of Trinidad in the Caribbean to ask how the choice of abundance currency influences the understanding of biodiversity change
This study investigated whether different currencies influenced our ecological understanding of the temporal change in FD experienced by tropical fish assemblages
Summary
Freshwater fishes are one of the most diverse vertebrate taxa (Magurran et al, 2011), and one of the most threatened because of multiple anthropogenic impacts including introductions of nonnative invasive species, modification and destruction of habitats and overexploitation (Albert et al, 2020; Dudgeon et al, 2006; Reid et al, 2019). The authors focused on functional diversity (FD), a facet of biodiversity that is gaining increasing attention in the literature (Laureto et al, 2015; Villéger et al, 2017), and for this they used data from rivers in the Northern Range on the island of Trinidad in the Caribbean to ask how the choice of abundance currency influences the understanding of biodiversity change. On the contrary, tends to scale positively with body size, which results in an inverse relationship between currencies If this relationship is not entirely symmetrical, biomass and numerical abundance will reveal different patterns of abundance structure. The authors addressed this question using numerical abundance and biomass data from tropical freshwater fish assemblages surveyed repeatedly over 5 years (Magurran et al, 2018). In light of the different emphases the two currencies give to species relative abundances, the authors predicted that they would provide different conclusions about the temporal FD patterns observed in these rivers
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