Patterns in species and functional dissimilarity: insights from periphytic algae in subtropical floodplain lakes

Abstract

Understanding spatial and temporal changes in species composition has long demanded the attention of ecologists. However, only recently questionsrelatedtochangesinspecies functionaltraits have been investigated. We explored patterns of species andfunctionaldissimilarity ofperiphyticalgae at six lakes sampled over a year across a subtropical floodplain. We evaluated the importance of turnover and nestedness components across space and time; the influence of environmental dissimilarity, spatial dis- tance,andtimeonspecies andfunctionaldissimilarity; and whether functional dissimilarity results from non- stochastic assembly processes. We used six functional traits to describe 155 species. Functional dissimilarity was estimated by functional dendrograms, and stochasticity was evaluated using null models. The turnover component was greater than nestedness for species and functional dissimilarity. Environmental dissimilarity, spatial distance, or time did not signif- icantly explain species or functional dissimilarity. However, functional dissimilarity was significantly greater than expected given the observed species dissimilarity. The main finding of this study is that communityassemblywasdeterministicwithrespectto traits. Further, each lake contributed similarly to the overall species and traits pool. These results highlight the importance of comparing species and functional dissimilarities to reach a better understanding of the organization of periphytic algal communities.