Evaluating drivers and patterns of aquatic community distribution in Neotropical floodplain systems : an approach based on beta-diversity analyses.

Abstract

Evaluating patterns and predictors of species distribution is important, because anthropogenic actions have been threatening global biodiversity. Hence, researchers have used measures of beta-diversity, defined as the variation in species composition amongst sites of a given area. Several measures of beta-diversity have been created, because using this approach makes it simple to elaborate and test ecological hypotheses, considering species distribution. Here, it was aimed to contribute to the knowledge about drivers and patterns of distribution amongst aquatic communities in Neotropical riverine floodplains. For this, this thesis was fractionated into two approaches, in which was used two different methods to measure beta-diversity. In the first approach, it was assessed the environmental and spatial factors affecting the beta-diversity facets (species-, traits- and phylogeny-based), and their components (Beta-total, replacement and richness difference), of ostracod communities associated with macrophytes, in the Upper Paraná River floodplain. Furthermore, it was compared these factors amongst the different life forms: emergent, rooted floating, rooted submerged, free submerged and free floating. In the second approach, it was used the local contribution to beta-diversity approach (LCBD) to evaluate the drivers and patterns of ecological uniqueness of the sites, in terms of species composition, in four floodplain systems, Amazon, Araguaia, Pantanal and Paraná. It was gathered data on community composition for eight aquatic biological groups: phytoplankton, ciliates, testate amoebae, rotifers, cladocerans, copepods, ostracods and fish. In general, environmental filtering was more important in explaining distribution patterns of communities, and the species sorting mechanism might be responsible for them, within and amongst the floodplains. In the first approach, different environmental and spatial factors influenced each of the beta-diversity facets of ostracod communities (species-, traits- and phylogeny-based). The factors affecting ostracod beta-diversity were different amongst the macrophyte life forms, evidencing the importance of considering them in ecological surveys of associated communities. In the second approach, the Amazon and Paraná floodplains had higher uniqueness in terms of species composition, showing the importance of conservation actions in these ecosystems. Furthermore, the drivers (e.g. environmental variables) and patterns of LCBD were different amongst the different biological groups, evidencing the need to include a variety of taxa. It was considered that the results of this thesis, based on beta-diversity analyses, contributed to a better understanding of drivers and patterns of distribution amongst communities in Neotropical floodplains. This is because researchers can use them as a reference in conservation and restoration plans for these systems and to prevent the destruction of areas with high conservation value, for example, by the construction of dams and reservoirs.