Amazonian lotic ecosystems are among the environments that have received most attention in studies on species distribution. This is related to the presence of high environmental complexity and spatial variation in these ecosystems, thus it is necessary to elucidate how such conditions affect the species distribution in response to habitat specificity and dispersion under different scales. Thus, in this thesis we aim to evaluate how environmental and spatial factors structure semi-aquatic bug (Hemiptera: Gerromorpha) communities in Amazonian streams. To achieve this goal, the thesis was divided into three chapters. First, we evaluated factors that structure metacommunities, considering environmental factors, linear and fluvial spatial structure within a drainage basin. We observed that the effect of the environment had greater effect on metacommunity structure and only factors related to river dispersion were important for these response. Thus, at basin scale, the metacommunity structure was affected mainly by species sorting and mass effects was associated to dispersion in smaller scales within basin network. In second chapter, we analyzed the patterns of metacommunities of semiaquatic bugs among different biogeographic areas of the Amazon region, we found that the limitation of community variation across space was decisive in structuring the diversity of assemblies. These results showed that high turnover occurs within the ecoregions evaluated due to environmental heterogeneity. In addition, beta diversity between different biogeographic areas in Amazon region evidenced general patterns of decay of similarity due to environmental and spatial distances. In the third chapter, we deconstructed the assemblages between wingless and winged individuals to evaluate the alteration of the environment in areas with anthropic alteration. We find that the composition of winged species assemblages differs from the total community composition, however, assemblages of winged and winged species showed responses associated with the loss of diversity caused by anthropic activity. However, the environmental variables that structure these assemblies were different, indicating that a trade-off occurs between reproduction (wingless) and dispersion (winged) to reach the fitness of these populations. In general, we highlight that characteristics of the aquatic habitat on a local scale, and the fluvial connectivity between habitats are the main determinants in structuring the communities of these organisms at a basin scale. Considering biogeographic scales, the limitation of the dispersion through space was the main factor in the structure of the communities, however, the beta diversity between regions also showed to be dependent on local factors. We consider that the specificity of these organisms to live on the surface of the water, besides showing strong relation with this habitat, also shows that the locomotion on the water surface is the main dispersion mechanism of these organisms in the basin network. In addition, the processes that have determined communities' patterns of diversity act on local scales up to biogeographic scales. However, we highlight that advances in the impacts of anthropic activities in the Amazon can also interfere in these processes and act on the distribution of species among the lotic ecosystems of the region.
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