Drivers of phytoplankton richness and diversity components in Neotropical floodplain lakes, from small to large spatial scales

Understanding the distribution patterns of species and how spatial and environmental factors drive the structure of communities is crucial to the preservation of biodiversity. We evaluate, during the low and high water periods, the phytoplankton diversity in lakes of four Brazilian floodplain systems (FPs): Amazon, Araguaia, Pantanal, and Paraná. We hypothesized that (i) species variation/replacement among floodplains (β2) is the predominant mechanism in shaping phytoplankton gamma diversity; (ii) the variation in phytoplankton taxonomic composition within each floodplain (β1) is mainly governed by local environmental conditions due to the high dispersal ability of phytoplankton at small spatial scales; and (iii) variation in the phytoplankton taxonomic composition among floodplains (β2) is mainly influenced by dispersal limitation. Variation partitioning was used to evaluate the influence of spatial and environmental factors on species richness. Higher γ diversity was found in the Araguaia and Amazon FPs. The high contribution of β2 (large scale) to γ diversity revealed the high degree of environmental heterogeneity in each floodplain. β1 (small scale) was more influenced by environmental variables, and β2 by both spatial and environmental factors. Our findings showed that γ diversity was explained by the interaction between the two factors, and that these processes influencing variation were scale dependent.