The relative influence of the environment, land use, and space on the functional and taxonomic structures of phytoplankton and zooplankton metacommunities in tropical reservoirs

Disentangling the effects of space and the environment on species distribution is one of the current goals of ecology and biogeography. In this study, we aimed to determine the relative influence of local, spatial (directional and non-directional), and land-use predictors on the taxonomic and functional trait compositions of phytoplankton and zooplankton assemblages. We collected data from 25 sampling points within shallow artificial water reservoirs in the central-western region of Brazil. This study was conducted in an area with a small spatial extent (<50 km between sampling sites) and in a reservoir of a typical hierarchical branching river network. The explanatory variables included 8 environmental features, 2 land-use predictors, and 2 spatial proxies (non-directional and directional spatial eigenvectors). We used a partial redundancy analysis to evaluate the relative influence of each predictor. Only spatial predictors, mainly directional, were important in explaining the phytoplankton and zooplankton metacommunity structure (functional and taxonomic). According to the metacommunity perspective, our results indicated that the phytoplankton and zooplankton metacommunities could be classified as species sorting with high dispersal, that is, a mass-effect perspective. We expected to see mass-effect processes in our study area, in which highly-dispersive species occur in a small-scale, highly-connected area where upstream reservoirs act as sources for dispersing species downstream. Moreover, some functional traits and morphofunctional attributes of phytoplankton (presence of flagella and small size) and zooplankton (suspensivore, carnivore, and littoral habitats) were associated with an increase in dispersal. Finally, this study contributes to the understanding of how environment, space, and land-use components structure plankton metacommunities.