What drives zooplankton taxonomic and functional β diversity? A review of Brazilian rivers

We carried out a literature review to investigate the taxonomic and functional beta diversity of zooplankton and its species replacement (beta repl) and richness difference (beta rich) components in Brazilian rivers. In addition, the taxonomic (LCBD-t) and functional ecological uniqueness (LCBD-f) were also measured. We tested the following hypotheses: (i) The beta repl component is the main driver of taxonomic beta diversity, while beta rich is most important for functional beta diversity, due to functional simplification; (ii) Sites with lower taxonomic and functional richness are the ones that most contribute to LCBD. Contrary to expectations, beta rich drove the taxonomic and functional beta diversity. This may have occurred due to environmental constraints and geographic distance, thus causing a loss or gain of species and traits between hydrographic regions. For just two regions, the sites with the lowest functional richness were the ones that most contributed to LCBD-f. This reinforces that sites with lower richness can support species that perform unique functions in the ecosystem. As studies involving zooplankton from lotic systems are still limited in Brazil, we suggest that future research should consider the patterns of beta diversity in these dynamic, diverse, and threatened aquatic ecosystems.