Distance decay as a descriptor of the diatom compositional variation in tropical reservoirs

Abstract

In the present study, distance decay was used as a descriptor of the compositional variation in diatom communities’ similarity between different habitats (phytoplankton and surface sediment) and seasons (summer and winter; only for phytoplankton) along a geographical gradient of ~64km over six reservoirs located in south-east Brazil. Whether rates of decay in similarity changed with distance in tropical biological communities was tested, and the degree to which dispersal (geographic distance) and niche (habitat association) processes explain variation in the diatom communities was estimated. In addition, whether the diatom assemblage captured in the surface sediment reflected the water column assemblage events was evaluated. Distance–decay curves were estimated using linear regressions. Partial Mantel tests were performed to examine the significance of relationships among the biological, environmental and spatial datasets. Similarity decreased significantly with distance between habitats and seasons, but the results were not statistically significant for surface sediment assemblages. All diatom communities were controlled more by limited dispersal than by environmental factors, probably as a result of the water quality and scale of the study area.