Influência dos fatores ambientais sobre a estrutura de comunidade de peixes em diferentes ambientes aquáticos na Amazônia

Abstract

Species diversity varies over time and space as a reflection of resource availability, suitable conditions, and biotic interactions that can locally exclude species from the regional pool. Understanding the causes of species variations remains challenging for ecologists. Still, it is already known that both biotic (interactions) and local environmental conditions (abiotic variables) are important factors in determining fish richness and abundance. Environmental conditions act differently in various aquatic ecosystems, structuring fish assemblages differently. In this context, the central objective of this thesis was to evaluate how local and regional environmental factors influence fish assemblage structure in different aquatic ecosystems in the southwest Amazon. Firstly, we assessed how the environment affects fish assemblages in river beaches. Next, we evaluated how local and regional environments influence the fish assemblage structure associated with aquatic macrophyte banks in lake environments. Finally, we examined how stream fish assemblage structure responds answered to local and regional environmental factors. In beach habitats, we found that temperature, dissolved oxygen, and depth were important in determining variation in fish species composition, while the temperature was the only variable influencing species richness. For fish in macrophyte banks habitats, the results indicated that both local and regional environmental variables (space and hydrological period) influenced fish assemblage structure. The variables depth of macrophyte bank, bank size, and space were significant for species richness. For species composition, environmental factors such as macrophyte composition, bank size, macrophyte richness, and regional variables such as space and hydrological period were influential, with the hydrological period being the strongest predictor of this variation, showing that flood pulses are a strong determinant in the structure of fish assemblages associated with macrophyte banks in Amazonian floodplains. Finally, we evaluated the influence of local, regional (landscape), and spatial factors on fish assemblage structure in upland streams in western Amazonia. The percentage of forest and spatial component (identity of Conservation Units) influenced species richness. Meanwhile, physical habitat and spatial variables influenced species composition, indicating that the fish assemblage in Amazonian streams answered to intact environments and habitat characteristics capable of supporting the persistence of these assemblages within and between watersheds.