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Steep clines within a highly permeable genome across a hybrid zone between two subspecies of the European rabbit

Authors

  • Miguel Carneiro,

    Corresponding author
    1. CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, Vairão, Portugal
    2. Departamento de Biologia da Faculdade de Ciências, Universidade do Porto, Porto, Portugal
    3. Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA
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  • Stuart J. E. Baird,

    1. CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, Vairão, Portugal
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  • Sandra Afonso,

    1. CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, Vairão, Portugal
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  • Esther Ramirez,

    1. IREC, Instituto de Investigación en Recursos Cinegéticos (CSIC-UCLM-JCCM), Ciudad Real, Spain
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  • Pedro Tarroso,

    1. CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, Vairão, Portugal
    2. Departamento de Biologia da Faculdade de Ciências, Universidade do Porto, Porto, Portugal
    3. CNRS, Institut des Sciences de l'Evolution CC 061, Université Montpellier 2, Montpellier, Cedex 05, France
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  • Henrique Teotónio,

    1. Instituto Gulbenkian de Ciência, Oeiras, Portugal
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  • Rafael Villafuerte,

    1. Instituto de Investigación en Recursos Cinegéticos (CSIC-UCLM-JCCM), Departamento de Zoología, Universidad de Córdoba, Córdoba, Spain
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  • Michael W. Nachman,

    1. Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA
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  • Nuno Ferrand

    1. CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, Vairão, Portugal
    2. Departamento de Biologia da Faculdade de Ciências, Universidade do Porto, Porto, Portugal
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Abstract

Maintenance of genetic distinction in the face of gene flow is an important aspect of the speciation process. Here, we provide a detailed spatial and genetic characterization of a hybrid zone between two subspecies of the European rabbit. We examined patterns of allele frequency change for 22 markers located on the autosomes, X-chromosome, Y-chromosome and mtDNA in 1078 individuals sampled across the hybrid zone. While some loci revealed extremely wide clines (≥ 300 km) relative to an estimated dispersal of 1.95–4.22 km/generation, others showed abrupt transitions ( 10 km), indicating localized genomic regions of strong selection against introgression. The subset of loci showing steep clines had largely coincident centers and stepped changes in allele frequency that did not co-localize with any physical barrier or ecotone, suggesting that the rabbit hybrid zone is a tension zone. The steepest clines were for X- and Y-chromosome markers. Our results are consistent with previous inference based on DNA sequence variation of individuals sampled in allopatry in suggesting that a large proportion of each genome has escaped the overall barrier to gene flow in the middle of the hybrid zone. These results imply an old history of hybridization and high effective gene flow and anticipate that isolation factors should often localize to small genomic regions.

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