compositional divergence and convergence in local communities and spatially structured landscapes的发散和收敛在当地社区和空间结构化的风景.pdfVIP

Compositional Divergence and Convergence in Local Communities and Spatially Structured Landscapes 1 1,2 1 Tancredi Caruso *, Jeff R. Powell , Matthias C. Rillig ¨ ¨ 1 Institut fur Biologie, Plant Ecology, Freie Universitat Berlin, Berlin, Germany, 2 Hawkesbury Institute for the Environment, University of Western Sydney, Richmond, New South Wales, Australia Abstract Community structure depends on both deterministic and stochastic processes. However, patterns of community dissimilarity (e.g. difference in species composition) are difficult to interpret in terms of the relative roles of these processes. Local communities can be more dissimilar (divergence) than, less dissimilar (convergence) than, or as dissimilar as a hypothetical control based on either null or neutral models. However, several mechanisms may result in the same pattern, or act concurrently to generate a pattern, and much research has recently been focusing on unravelling these mechanisms and their relative contributions. Using a simulation approach, we addressed the effect of a complex but realistic spatial structure in the distribution of the niche axis and we analysed patterns of species co-occurrence and beta diversity as measured by dissimilarity indices (e.g. Jaccard index) using either expectations under a null model or neutral dynamics (i.e., based on switching off the niche effect). The strength of niche processes, dispersal, and environmental noise strongly interacted so that niche-driven dynamics may result in local communities that either diverge or converge depending on the combination of these factors. Thus, a fundamental result i