Mathew A. Leibold1, Lissete N DeSenerpont-Domis1, Jelena H Pantel1, Jennifer G Howeth1, Jonathan G Cox1, Genevieve Smith1, Mary K. Johnston1, Maria J La Roca1, and Pedro R. Peres-Neto2. (1) University of Texas at Austin, (2) University of Quebec at Montreal
Background/Question/Methods Work to date on metacommunities indicates that they can be regulated by a complex array of processes. Key to much of metacommunity pattern seems to be the process of species sorting in which species composition of communities track environmental conditions. However there is substantial evidence that there are also some important spatial dynamics that are independent of this. Theory also indicates that communities with heterogenous dispersal rates or with heterogeneity of niche breadth should show heterogeneity in the relative importance of species sorting versus spatial effects even though species share the same metacommunity. We hypothesize that much of the variation in the relative importance of species sorting versus spatial patterning might be explained by the relative dominance of species in local communities. We argue that the most common species in a given local community (i.e. ‘core’ species) should show stronger distributional patterns related to species sorting than do less common (or ‘satellite’) species. Results/Conclusions
We test this hypothesis using variance decomposition methods community composition as it scales with local dominance in two contrasting metacommunities. In one of these, trees on Barro Colorado island, previous work shows that dispersal limitation is weak so that mass effects and stochastic drift likely influence composition. In the other, zooplankton in lakes of the Northeastern US, previous work has shown that dispersal limitation is strong so that parch dynamics likely influence composition. In both cases we find support for the core-satellite hypothesis. Dominant species show stronger affinity to environmental conditions than do less dominant ones. In contrast, less dominant species show stronger affinity for spatial effects that reveal the influence of mass-effects, stochastic demography, and/or dispersal limitation. These results indicate that metacommunities are likely to be regulated by a mixture of processes rather than being easily categorized into broad classes such as pure species sorting, pure mass-effects, purely neutral, or pure patch dynamics.
