Are species–area relationships from entire archipelagos congruent with those of their constituent islands?

Authors

  • Ana M. C. Santos,

    Corresponding author
    1. Department of Biology, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK,
    2. Universidade dos Açores, Dep. de Ciências Agrárias – CITA-A (Azorean Biodiversity Group), Terra-Chã, 9700-851 Angra do Heroísmo, Portugal,
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  • Robert J. Whittaker,

    1. Biodiversity Research Group, Oxford University Centre for the Environment, South Parks Road, Oxford OX1 3QY, UK,
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  • Kostas A. Triantis,

    1. Universidade dos Açores, Dep. de Ciências Agrárias – CITA-A (Azorean Biodiversity Group), Terra-Chã, 9700-851 Angra do Heroísmo, Portugal,
    2. Biodiversity Research Group, Oxford University Centre for the Environment, South Parks Road, Oxford OX1 3QY, UK,
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  • Paulo A. V. Borges,

    1. Universidade dos Açores, Dep. de Ciências Agrárias – CITA-A (Azorean Biodiversity Group), Terra-Chã, 9700-851 Angra do Heroísmo, Portugal,
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  • Owen R. Jones,

    1. Department of Biology, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK,
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  • Donald L. J. Quicke,

    1. Department of Biology, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK,
    2. NERC Centre for Population Biology, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK,
    3. Department of Entomology, Natural History Museum, Cromwell Road, London SW7 5BD, UK
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  • Joaquín Hortal

    1. NERC Centre for Population Biology, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK,
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Errata

This article is corrected by:

  1. Errata: Corrigendum Volume 25, Issue 8, 1037, Article first published online: 3 July 2016

Ana M. C. Santos, Department of Biology, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK.
E-mail: ana.margarida.c.santos@googlemail.com

ABSTRACT

Aim  To establish the extent to which archipelagos follow the same species–area relationship as their constituent islands and to explore the factors that may explain departures from the relationship.

Location  Thirty-eight archipelagos distributed worldwide.

Methods  We used ninety-seven published datasets to create island species–area relationships (ISARs) using the Arrhenius logarithmic form of the power model. Observed and predicted species richness of an archipelago and of each of its islands were used to calculate two indices that determined whether the archipelago followed the ISAR. Archipelagic residuals (ArcRes) were calculated as the residual of the prediction provided by the ISAR using the total area of the archipelago, standardized by the total richness observed in the archipelago. We also tested whether any characteristic of the archipelago (geological origin and isolation) and/or taxon accounts for whether an archipelago fits into the ISAR or not. Finally, we explored the relationship between ArcRes and two metrics of nestedness.

Results  The archipelago was close to the ISAR of its constituent islands in most of the cases analysed. Exceptions arose for archipelagos where (i) the slopes of the ISAR are low, (ii) observed species richness is higher than expected by the ISAR and/or (iii) distance to the mainland is small. The archipelago's geological origin was also important; a higher percentage of oceanic archipelagos fit into their ISAR than continental ones. ArcRes indicated that the ISAR underpredicts archipelagic richness in the least isolated archipelagos. Different types of taxon showed no differences in ArcRes. Nestedness and ArcRes appear to be related, although the form of the relationship varies between metrics.

Main conclusions  Archipelagos, as a rule, follow the same ISAR as their constituent islands. Therefore, they can be used as distinct units themselves in large-scale biogeographical and macroecological studies. Departure from the ISAR can be used as a crude indicator of richness-ordered nestedness, responsive to factors such as isolation, environmental heterogeneity, number and age of islands.

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