Ecological uniqueness and species richness of zooplankton in subtropical floodplain lakes

Beta diversity can be analysed using various approaches, but those integrating site and species contributions to beta diversity are rare in floodplain lake systems. We analysed the beta diversity of rotifers and cladocerans across 50 floodplain lakes in Brazil, focusing on both pelagic and littoral zones. We partitioned beta diversity into local contributions (LCBD), species contributions (SCBD), and related LCBD with environmental variables and SCBD with species features. We expected lower species richness and higher ecological uniqueness for both groups in the pelagic zones than in the littoral zones. The highest ecological uniqueness and low species richness were detected in the pelagic zone, whereas the littoral zones had high species richness and low ecological uniqueness. We found a negative relationship between species richness and LCBD for rotifers, but no significant relationship was detected for cladocerans. Nitrate, transparency and conductivity affected variation in ecological uniqueness. Common and accessory species had higher contributions to beta diversity compared with rare species. The SCBD of rotifers and cladocerans showed similar responses based on occurrence and density data. We suggest that the use of zooplankton assemblages to determine conservation actions across floodplain lakes should be based on different biological groups and lake zones. The inclusion of littoral zones adds to our knowledge of zooplankton biodiversity that has typically been based on studies of pelagic zones, and may have implications for the conservation planning of floodplain lakes.