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More species, fewer specialists: 100 years of changes in community composition in an island biogeographical study

Authors

  • Kerbiriou Christian,

    Corresponding author
    1. Muséum National d’Histoire Naturelle, UMR 5173, Conservation Restauration et Suivi des Populations, 55 rue Buffon, 75005 Paris, France
      *Kerbiriou Christian, Muséum National d’Histoire Naturelle, UMR 5173, Conservation Restauration et Suivi des Populations, 55 rue Buffon, 75005 Paris, France.
      E-mail: kerbiriou@mnhn.fr
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  • Le Viol Isabelle,

    1. Muséum National d’Histoire Naturelle, UMR 5173, Conservation Restauration et Suivi des Populations, 55 rue Buffon, 75005 Paris, France
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  • Jiguet Frédéric,

    1. Muséum National d’Histoire Naturelle, UMR 5173, Conservation Restauration et Suivi des Populations, 55 rue Buffon, 75005 Paris, France
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  • Devictor Vincent

    1. Department of Zoology, Edward Grey Institute, University of Oxford, Oxford OX1 3PS, UK
    2. Sation Biologique de la Tour du Valat, Le Sambuc, F-13200 Arles, France
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*Kerbiriou Christian, Muséum National d’Histoire Naturelle, UMR 5173, Conservation Restauration et Suivi des Populations, 55 rue Buffon, 75005 Paris, France.
E-mail: kerbiriou@mnhn.fr

Abstract

Aim  We measured the changes in an island avifauna over more than 100 years (1898–2006), using community indices accounting for difference in expected species sensitivity to land-use and climate changes.

Location  Ouessant Island, France, Great Britain.

Methods  We assessed the temporal trend of the relative proportion of generalist species breeding on Ouessant island and whether high-temperature tolerant species have replaced less tolerant species over this time period. We further tested the relationship between the observed change in the avifauna composition, and long-term population species’ trends measured independently in potential source regions of colonist species (France and Great Britain).

Results  During the whole study period, Ouessant island has experienced a strong increase in species richness (+41%), but a severe decline in specialist species. In contrast, we found no change in species composition in terms of their temperature-tolerance. The observed trend was highly correlated with species trends measured in the Great Britain.

Main conclusions  Our results revealed an ongoing biotic homogenization process towards more generalist species, coupled with a strong local increase in species richness. The observed trend was most likely driven by a strong habitat change in the island occurring during the period considered, favouring the colonization of generalist species. Our results show that an increase in species richness can be misinterpreted as a sign of conservation improvement and that assessing change in community composition using species-specific ecological traits provides more accurate insights for conservation planning purposes.

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