The role of dispersal in shaping plant community composition of wetlands within an old-growth forest

Authors

  • Kathryn M. Flinn,

    Corresponding author
    1. Department of Biology, McGill University, 1205 Docteur Penfield, Montréal QC H3A 1B1, Canada
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    • Present addresses: Department of Biology, Emory & Henry College, P.O. Box 947, Emory, VA 24327, USA.

  • Tarik C. Gouhier,

    1. Department of Biology, McGill University, 1205 Docteur Penfield, Montréal QC H3A 1B1, Canada
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    • Department of Zoology, Oregon State University, 3029 Cordley Hall, Corvallis, OR 97331, USA.

  • Martin J. Lechowicz,

    1. Department of Biology, McGill University, 1205 Docteur Penfield, Montréal QC H3A 1B1, Canada
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  • Marcia J. Waterway

    1. Department of Plant Science, McGill University, 21111 Lakeshore Road, Ste. Anne de Bellevue QC H9X 3V9, Canada
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*Correspondence author. E-mail: kflinn@ehc.edu

Summary

1. Dispersal ability can influence the importance of dispersal relative to other processes organizing metacommunities, such as species sorting among habitats along environmental gradients.

2. We compare plants with different dispersal modes and habitat affinities, evaluating the roles of environmental and spatial controls on plant community composition in 128 wetlands within 10 km2 of old-growth maple–beech forest in southern Québec, Canada.

3. We address two hypotheses. First, we ask whether species with short-distance dispersal mechanisms are more dispersal-limited than species with adaptations for long-distance dispersal. Second, because wetland habitats are more fragmented than upland habitats in this forested area, we test the hypothesis that wetland species are more dispersal-limited than upland species growing in the same wetlands (e.g. on hummocks within a swamp).

4. Variation partitioning based on constrained ordinations showed that the distributions of species with short-distance dispersal mechanisms related more strongly to spatial factors than the distributions of long-distance dispersers, supporting the interpretation that these species are more dispersal-limited. The distributions of short-distance dispersers also showed finer-scale spatial patterns than the distributions of long-distance dispersers.

5. Distributions of wetland species related more strongly to environmental conditions than the distributions of upland species growing in the same wetlands, suggesting that wetland species are actually less dispersal-limited than upland species. Wetland and upland species had similar patterns of spatial variation in community composition.

6.Synthesis. The processes of dispersal limitation and species sorting along environmental gradients have differential importance to plants that grow within the same communities, but differ in dispersal ability and habitat affinity. This result emphasizes the impact of dispersal ability on the organization of metacommunities.

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