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Testing Darwin’s naturalization hypothesis in the Azores

Authors

  • Hanno Schaefer,

    1. Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot SL5 7PY, UK
    2. CITA-A, Azorean Biodiversity Group, Universidade dos Açores, Terra Chã, 9700-851 Angra do Heroísmo, Portugal
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    • Correspondence and present address: Organismic and Evolutionary Biology, Harvard University, 22 Divinity Avenue, Cambridge, MA 02138, USA. E-mail: hschaef@fas.harvard.edu

  • Olivier J. Hardy,

    1. Evolutionary Biology and Ecology Unit, Faculté des Sciences, Université Libre de Bruxelles, Avenue F. Roosevelt 50, B-1050 Brussels, Belgium
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  • Luís Silva,

    1. CIBIO-Açores, Department of Biology, Universidade dos Açores, Rua Mãe de Deus 58, 9501-801 Ponta Delgada, Portugal
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  • Timothy G. Barraclough,

    1. Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot SL5 7PY, UK
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  • Vincent Savolainen

    1. Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot SL5 7PY, UK
    2. Royal Botanical Gardens, Kew, Richmond, Surrey TW9 3DS, UK
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Abstract

Ecology Letters (2011) 14: 389–396

Abstract

Invasive species are a threat for ecosystems worldwide, especially oceanic islands. Predicting the invasive potential of introduced species remains difficult, and only a few studies have found traits correlated to invasiveness. We produced a molecular phylogenetic dataset and an ecological trait database for the entire Azorean flora and find that the phylogenetic nearest neighbour distance (PNND), a measure of evolutionary relatedness, is significantly correlated with invasiveness. We show that introduced plant species are more likely to become invasive in the absence of closely related species in the native flora of the Azores, verifying Darwin’s ‘naturalization hypothesis’. In addition, we find that some ecological traits (especially life form and seed size) also have predictive power on invasive success in the Azores. Therefore, we suggest a combination of PNND with ecological trait values as a universal predictor of invasiveness that takes into account characteristics of both introduced species and receiving ecosystem.

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