Dispersal as a limiting factor in the colonization of restored mountain streams by plants and macroinvertebrates

Authors

  • Robert J. Brederveld,

    1. Ecology & Biodiversity Group, Department of Biology, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands
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    • Present addresses: Witteveen+Bos Consulting Engineers, Ecology group, PO Box 233, 7400 AE Deventer, The Netherlands.

  • Sonja C. Jähnig,

    1. Department of Applied Zoology/Hydrobiology, University of Duisburg-Essen, D-45117 Essen, Germany
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    • Department of Limnology and Conservation, Senckenberg Research Institute and Natural History Museum, Clamecystrasse 12, 63571 Gelnhausen, Germany; Biodiversity and Climate Research Centre (BiK-F), Senckenberganlage 25, Frankfurt am Main D-60325, Germany.

  • Armin W. Lorenz,

    1. Department of Applied Zoology/Hydrobiology, University of Duisburg-Essen, D-45117 Essen, Germany
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  • Stefan Brunzel,

    1. Department of Animal Ecology, Faculty of Biology, Philipps-Universität Marburg, Karl von Frisch-Str. 8, 35032 Marburg, Germany
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  • Merel B. Soons

    Corresponding author
    1. Ecology & Biodiversity Group, Department of Biology, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands
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Correspondence author. E-mail: m.b.soons@uu.nl

Summary

1. Over the past centuries, European streams have been heavily influenced by humans through pollution and regulation. As a result, the quality and diversity of freshwater riparian habitats have declined strongly, and the diversity of riparian flora and fauna has decreased. Recent restoration measures have resulted in stream habitat improvements, but biodiversity improvements have failed to follow in fragmented streams. It has been suggested that dispersal limitation could play an important role in the lack of biodiversity improvement in restored streams, but to date, there is no conclusive evidence for this assumption.

2. In this study, we investigated whether colonization of restored streams by plants and macroinvertebrates is limited by dispersal. We hypothesized that colonization success increases with increasing availability of (nearby) source populations and with increasing ability of species to disperse over long distances. We related species composition in seven restored stream sections to species’ abundances in the surroundings and to species’ dispersal abilities.

3. For both plants and macroinvertebrates, colonization success is strongly related to the abundance of species in the local and regional species pools.

4. For plants, dispersal strategy has an additional influence on colonization success: short-lived plants with high production of small, well-dispersed seeds colonized best within the 3- to 5-year period after restoration.

5. The existence of dispersal strategy constraints could not be confirmed in macroinvertebrates, possibly because these are limited by a lack of connectivity on larger spatial scales. On the landscape scale, beneficial effects of increased plant diversity might further improve habitat suitability for macroinvertebrates.

6.Synthesis and applications. Dispersal appears to be a limiting factor for successful (re)colonization of restored streams in fragmented landscapes. In plants, this is attributed to limitations in seed dispersal abilities and likely to a lack of nearby source populations as well. In macroinvertebrates, lack of nearby source populations may also be a limiting factor. Hence, we suggest restoring landscape connectivity at larger spatial scales and optimizing the availability of near-natural ‘source’ areas in the vicinity of restoration projects, at least for plants, to improve the success of biodiversity restoration in fragmented habitats.

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