Biogeography of western Mediterranean butterflies: combining turnover and nestedness components of faunal dissimilarity

Authors

  • Leonardo Dapporto,

    1. Department of Biological and Medical Sciences, Centre for Ecology, Environment and Conservation, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford, UK
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  • Simone Fattorini,

    Corresponding author
    1. Departamento de Ciências Agrárias, Azorean Biodiversity Group (GBA, CITA-A) and Platform for Enhancing Ecological Research & Sustainability (PEERS), Universidade dos Açores, Rua Capitão João d′Ávila, Pico da Urze, Angra do Heroísmo, Terceira, Azores, Portugal
    • Correspondence: Simone Fattorini, Azorean Biodiversity Group (GBA, CITA-A) and Platform for Enhancing Ecological Research & Sustainability (PEERS), Departamento de Ciências Agrárias, Universidade dos Açores, Rua Capitão João d′Ávila, Pico da Urze, 9700-042, Angra do Heroísmo, Terceira, Azores, Portugal.

      E-mail: simone_fattorini@virgilio.it

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  • Raluca Vodă,

    1. Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Spain
    2. Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, Spain
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  • Vlad Dincă,

    1. Department of Zoology, Stockholm University, Stockholm, Sweden
    2. Biodiversity Institute of Ontario, University of Guelph, Guelph, Ontario, Canada
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  • Roger Vila

    1. Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Spain
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Abstract

Aim

Unpartitioned dissimilarity indices such as the Sørensen index (βsor) tend to categorize areas according to species number. The use of turnover indices, such as the Simpson index (βsimp), may lead to the loss of important information represented by the nestedness component (βnest). Recent studies have suggested the importance of integrating nestedness and turnover information. We evaluated this proposition by comparing biogeographical patterns obtained by unpartitioned (βsor) and partitioned indices (βsimp and βnest) on presence data of western Mediterranean butterflies.

Location

Western Mediterranean.

Methods

We assessed the regionalization of 81 mainland and island faunas according to partitioned and unpartitioned dissimilarity by using cluster analyses with the unweighted pair-group method using arithmetic averages (UPGMA) combined with non-metric multidimensional scaling (NMDS). We also carried out dissimilarity interpolation for βsor, βsimp, βnest and the βnestsor ratio, to identify geographical patterns of variation in faunal dissimilarity.

Results

When the unpartitioned βsor index was used, the clustering of sites allowed a clear distinction between insular and mainland species assemblages. Most islands were grouped together, irrespective of their mainland source, because of the dominant effect of their shared low richness. βsimp was the most effective index for clustering islands with their respective mainland source. βsimp clustered mainland sites into broader regions than clusters obtained using βsor. A comparison of regionalization and interpolation provided complementary information and revealed that, in different regions, the patterns highlighted by βsor could largely be determined either by nestedness or turnover.

Main conclusions

Partitioned and unpartitioned indices convey complementary information, and are able to reveal the influence of historical and ecological processes in structuring species assemblages. When the effect of nestedness is strong, the exclusive use of turnover indices can generate geographically coherent groupings, but can also result in the loss of important information. Indeed, various factors, such as colonization–extinction events, climatic parameters and the peninsular effect, may determine dissimilarity patterns expressed by the nestedness component.

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