From species to communities: The scaling of biodiversity.
Storch, David*,1, 2, 1 Center for Theoretical Study, Charles University, Jilská 1, Praha 1, Czech Republic2 Department of Ecology, Faculty of Sciences, Charles University, Viničná 7, Praha 2, Czech Republic
ABSTRACT- One of the most important questions in ecology is whether the properties of local communities or large species assemblages can be derived purely from the knowledge of patterns occuring at the species level, or whether at least some assumptions of interspecific interactions are needed for the prediction of these emergent properties. I will show, using extensive data sets on avian distribution on continental scales, that two major macroecological patterns concerning species richness, the species-area and species-energy relationships, as well as the interaction between these two patterns, can be derived on the basis of very simple assumptions concerning spatial distribution of individual species. Namely, the slope and shape of the species-area relationship on a continental scale can be derived from the knowledge of frequency distribution of species relative occupancies and the assumption of random spatial aggregation on several spatial scales, whereas the slope of the species-energy relationship as well as the distribution of species along the productivity gradient are predicted by a simple simulation model assuming stochastic range dynamics modulated by productivity. This approach also predicts lower slope of the species-area relationship in more productive areas (and vice versa), which is also supported by the data. All these findigs indicate that the emergent properties of multispecies assemblages may not depend on interspecific interactions related to any sort of biotic saturation, and can be understood as an outcome of scaling properties of distributions of individual species which behave in an individualistic manner. This does not rules out, however, the role of competition and saturation effects in shaping the overall distribution of species occupancies and/or abundancies, nor their importance for local community patterns. Anyway, null models of multispecies patterns should consider geometric and biological constraints independently imposed upon the distribution of individual species before involving complex interspecific interactions.
Key words: birds, null models, richness-productivity relationship, species-area relationship
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