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Why is adaptation prevented at ecological margins? New insights from individual-based simulations


  • Jon R. Bridle,

    Corresponding author
    1. Institute of Zoology, Zoological Society of London, Regent’s Park, London NW1 4RY, UK
    2. School of Biological Sciences, University of Bristol, Bristol BS8 1UD, UK
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  • Jitka Polechová,

    1. Biomathematics & Statistics Scotland, JCMB, King’s Buildings, Edinburgh EH9 3JZ, UK
    2. IST Austria (Institute of Science and Technology Austria), Am Campus 1, Klosterneuburg A-3400, Austria
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  • Masakado Kawata,

    1. Division of Ecology and Evolutionary Biology, Graduate School of Life Sciences, Tohoku University, Sendai 980-8578, Japan
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  • Roger K. Butlin

    1. Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
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  • All authors contributed equally to this publication.

* Correspondence:


Ecology Letters (2010) 13: 485–494


All species are restricted in their distribution. Currently, ecological models can only explain such limits if patches vary in quality, leading to asymmetrical dispersal, or if genetic variation is too low at the margins for adaptation. However, population genetic models suggest that the increase in genetic variance resulting from dispersal should allow adaptation to almost any ecological gradient. Clearly therefore, these models miss something that prevents evolution in natural populations. We developed an individual-based simulation to explore stochastic effects in these models. At high carrying capacities, our simulations largely agree with deterministic predictions. However, when carrying capacity is low, the population fails to establish for a wide range of parameter values where adaptation was expected from previous models. Stochastic or transient effects appear critical around the boundaries in parameter space between simulation behaviours. Dispersal, gradient steepness, and population density emerge as key factors determining adaptation on an ecological gradient.