Interactive effects of disturbance and dispersal directionality on species richness and composition in metacommunities

Authors

  • Florian Altermatt,

    1. Department of Environmental Science and Policy, University of California, 1 Shields Avenue, Davis, California 95616 USA
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    • Present address: Department of Aquatic Ecology, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, CH-8600 Dübendorf, Switzerland. E-mail: faltermatt@bluewin.ch

  • Sebastian Schreiber,

    1. Department of Evolution and Ecology, University of California, 1 Shields Avenue, Davis, California 95616 USA
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  • Marcel Holyoak

    1. Department of Environmental Science and Policy, University of California, 1 Shields Avenue, Davis, California 95616 USA
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Abstract

Dispersal among ecological communities is usually assumed to be random in direction, or to vary in distance or frequency among species. However, a variety of natural systems and types of organisms may experience dispersal that is biased by directional currents or by gravity on hillslopes. We developed a general model for competing species in metacommunities to evaluate the role of directionally biased dispersal on species diversity, abundance, and traits. In parallel, we tested the role of directionally biased dispersal on communities in a microcosm experiment with protists and rotifers. Both the model and experiment independently demonstrated that diversity in local communities was reduced by directionally biased dispersal, especially dispersal that was biased away from disturbed patches. Abundance of species (and composition) in local communities was a product of disturbance intensity but not dispersal directionality. High disturbance selected for species with high intrinsic growth rates and low competitive abilities. Overall, our conclusions about the key role of dispersal directionality in (meta)communities seem robust and general, since they were supported both by the model, which was set in a general framework and not parameterized to fit to a specific system, and by a specific experimental test with microcosms.

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