Landscape heterogeneity and marine subsidy generate extensive intrapopulation niche diversity in a large terrestrial vertebrate

Authors

  • Chris T. Darimont,

    Corresponding author
    1. Department of Biology, PO Box 3020, Station CSC, University of Victoria, Victoria, BC, Canada V8W 3N5;
    2. Raincoast Conservation Foundation, PO Box 86, Denny Island, BC, Canada V0T 1B0; and
      Correspondence author. Environmental Studies Department, University of California, Santa Cruz, 405 Interdisciplinary Sciences Building, 1156 High Street, Santa Cruz, CA 95064, USA. E-mail: darimont@ucsc.edu
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  • Paul C. Paquet,

    1. Raincoast Conservation Foundation, PO Box 86, Denny Island, BC, Canada V0T 1B0; and
    2. Faculty of Environmental Design, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4
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  • Thomas E. Reimchen

    1. Department of Biology, PO Box 3020, Station CSC, University of Victoria, Victoria, BC, Canada V8W 3N5;
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Correspondence author. Environmental Studies Department, University of California, Santa Cruz, 405 Interdisciplinary Sciences Building, 1156 High Street, Santa Cruz, CA 95064, USA. E-mail: darimont@ucsc.edu

Summary

  • 1Inquiries into niche variation within populations typically focus on proximate ecological causes such as competition. Here we examine how landscape heterogeneity and allochthonous (marine) subsidy might ultimately generate intrapopulation niche diversity.
  • 2Using stable isotope analysis, we detected extensive terrestrial–marine isotopic niche variation among subpopulations, social groups, and individual grey wolves (Canis lupus) that occupy a spatially heterogeneous landscape in coastal British Columbia comprising a mainland area and adjacent archipelago.
  • 3The inner island subpopulation exhibited the widest isotopic niche in the population, consuming extensive terrestrial and marine resources. Mainland and outer island subpopulations occupied comparatively narrow and primarily terrestrial, and primarily marine, niches respectively. Within these biogeographical subpopulations, social groups also diverged in niche.
  • 4To support examination at the individual level, we used an isotopic approach to test Van Valen's (1965) niche variation hypothesis. Consistent with the hypothesis, we observed that among-individual variation increased with subpopulation niche width.
  • 5Patterns at all levels related to how a spatially heterogeneous coastal landscape structured the competitive environment, which in turn mediated the availability and use of terrestrial and marine resources. Broadly, our results suggest that spatial heterogeneity and allochthonous subsidy – both widespread but commonly subject to contemporary anthropogenic change – might provide novel opportunities for examination and conservation of ecological variation within populations.

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