Metacommunity structure and dynamics

Freshwater biological communities are spatially distributed in relatively isolated patches over a terrestrial landscape matrix, but they may be connected through dispersal processes and can therefore be studied as a set of interrelated communities, constituting a metacommunity. In this chapter, we explore the different processes shaping metacommunity structure, and their relationship with diversity patterns. Besides evolution in the long term, there are three main ecological processes structuring metacommunities: environmental control, dispersal, and stochasticity. Environmental control (i.e., selection), also referred to as niche-control or species sorting, refers to the filtering effect of the environment by selecting species adapted to the abiotic and biotic conditions, working at local and regional scales. Another key process, whose role is highlighted by metacommunity theory, is dispersal, a scale-dependent process with a high influence on biodiversity. Finally, stochastic processes (e.g., ecological drift) can lead to unpredictable but important changes in community structure. Focusing on the influence of these mechanisms through different organisms and scales, we show how the relative roles of selection, dispersal, and drift are crucial in organizing tropical wetland metacommunities worldwide. We also illustrate how variation partitioning analysis, one of the most widely used methods for the study of empirical metacommunities, provides information about the major role of environmental, spatial, and neutral effects in tropical wetland metacommunity organization. Finally, we present some remarks on conservation biology under the lens of metacommunity theory, which assumes that not only local conditions but also the regional environment and connectivity are essential elements to be considered for successful management planning.