Empirical examples of natural metacommunities lag behind theoretical developments and therefore are needed to understand how the relative contributions of dispersal and environmental filtering varies taxonomically and in different environments. Here, we use the geographic distributions of ostracode species and their morphological traits in lakes on San Salvador Island, Bahamas to test the hypothesis that their metacommunity dynamics are dominated by species sorting. We sampled thirty-two lakes for ostracode abundance, morphological traits, and limnological variables. The abiotic environment of lakes was found to vary mostly independently of space, allowing for the evaluation of the distinct roles of spatial and environmental variables. Differences between assemblages were not found to be spatially auto-correlated, indicating that dispersal limitation of species is not an important factor influencing community assembly. Ostracode assemblages and community-weighted aggregated species’ traits were found to vary systematically with conductivity, alkalinity, and dissolved oxygen, showing that the abiotic environment is a strong filter. While conductivity did display low, but significant, spatial structure, halophilic species followed this spatial pattern. This environmental filter combined with no effects of dispersal is consistent with only a species sorting model. This study thus provides a valuable example of metacommunity models applied to a natural system by specifying the relevant ecological factors that govern community assembly.
Bibliographical noteFunding Information:
We would like to thank Dr. Donald T. Gerace, Chief Executive Officer, and Tom Rothfus, Executive Director of the Gerace Research Center, San Salvador, Bahamas and Erin Rothfus. We would also like to thank Sara Bright, Mark Dalman, Emily Draher, and Emily Woodward for providing field assistance as well as Krystal Kohlman and Tom Quick for providing laboratory assistance. Susan M. Kidwell, Jill Leonard-Pingel, Madeline Marshall, Peter Tierney, and Kristen Jenkins Voorhies provided valuable comments on previous versions of this paper. Andrew V. Michelson received funding from the University of Akron Department of Geology and Environmental Science, the University of Akron program in Integrated Bioscience, the University of Akron Graduate Student Government, and the Gerace Research Centre. Lisa E. Park Boush received funding from U.S. National Science Foundation (EAR 0851847). This work was conducted under Bahamas Permit G234 and G235 to Park Boush and was further supported by the National Science Foundation as part of the author's Individual Research Plan when she served as a Program Officer within the Earth Science Division of the Geoscience Directorate.
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- Environmental gradient
- San Salvador Island, Bahamas
- Species sorting
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