Efeitos do contexto espacial e hidroperíodo sobre a variação de comunidades em ambientes aquáticos

Abstract

One of the major goals of community ecology is to understand the processes that underline the composition and distribution of species. In aquatic environments, lentic systems have a wide range of environmental stabilities, presenting permanent or temporary waterbodies, due to changes in the hydroperiod. This variation can cause variation in species composition (or beta diversity) among sites. On the other hand, lotic systems, such as rivers and streams, have a dendritic configuration that can be fundamental to the variation in beta diversity. This thesis presents two studies that aim to analyse the effects of hydroperiod and spatial context on the composition of aquatic organisms. The first study refers to a global meta-analysis published in the journal Hydrobiologia, which aims to compare beta diversity among permanent and among temporary aquatic systems and to clarify if there is any pattern of beta diversity linked to hydroperiod. The second study consists of a mesocosm experiment that seeks to understand how the spatial context (sites in the periphery or center of the catchment) of dendritic systems influences the dynamics of aquatic communities. The results of the meta-analysis did not indicate a pattern of beta diversity in relation to the hydroperiod, with context-dependent factors (such as hydrology or species dispersal rates) being more determinant in the structuring of communities. However, our exploratory analyses suggest that organism group may mediate the difference of beta diversity among permanent and among temporary water bodies, with zooplankton (in contrast to benthic invertebrates) presenting a higher beta diversity among permanent than among temporary habitats. In the second study, the results did not indicate an influence of the network position on beta diversity. Nevertheless, a relationship between beta diversity and time sampling was demonstrated, with communities losing species and showing increasing variation in community composition over time.