Ecological Principles of Nature Conservation

Part of the series Conservation Ecology Series: Principles, Practices and Management pp 162-200

The Ecology of Dispersal in Relation to Conservation

  • Lennart HanssonAffiliated withDepartment of Wildlife Ecology, Swedish University of Agricultural Sciences
  • , Lars SöderströmAffiliated withDepartment of Plant Ecology, University of Umeå
  • , Christer SolbreckAffiliated withDepartment of Plant and Forest Protection, Swedish University of Agricultural Sciences

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Small populations easily become extinct (Goodman, 1987). Small populations may also be affected by genetic drift and inbreeding (Schonewald Cox et al, 1983), although the importance of these latter effects on population dynamics is less clear (Ehrlich, 1983; Shaffer, 1987; see also chapter 4). The adverse demographic and genetic processes in small populations are both counteracted by immigration. Such immigration should keep the density over a certain threshold level (Brown & Kodric–Brown, 1977) or supply at least one reproducing individual per generation (Schonewald–Cox et al., 1983) to circumvent extinction or loss of genetic variability. However, immigration of foreign competing or predating species may have negative effects on local and circumscribed communities (Helle & Järvinen, 1986).