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Genetic exchange across a hybrid zone within the Iberian endemic golden-striped salamander, Chioglossa lusitanica

Authors

  • F. SEQUEIRA,

    1. CIBIO/UP-Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Rua Padre Armando Quintas, 4485–661 Vairão, Portugal,
    2. Departamento de Zoologia e Antropologia, Faculdade de Ciências, Universidade do Porto, Praça Gomes Teixeira, 4099-002 Porto, Portugal,
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  • J. ALEXANDRINO,

    Corresponding author
    1. CIBIO/UP-Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Rua Padre Armando Quintas, 4485–661 Vairão, Portugal,
    2. Museum of Vertebrate Zoology, University of California, Berkeley, 3101 Valley Life Science Building # 3160, Berkeley, CA 94720–3160, USA
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  • S. ROCHA,

    1. CIBIO/UP-Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Rua Padre Armando Quintas, 4485–661 Vairão, Portugal,
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  • J. W. ARNTZEN,

    1. CIBIO/UP-Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Rua Padre Armando Quintas, 4485–661 Vairão, Portugal,
    2. National Museum of Natural History, PO Box 9517, 2300 RA Leiden, the Netherlands,
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  • N. FERRAND

    1. CIBIO/UP-Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Rua Padre Armando Quintas, 4485–661 Vairão, Portugal,
    2. Departamento de Zoologia e Antropologia, Faculdade de Ciências, Universidade do Porto, Praça Gomes Teixeira, 4099-002 Porto, Portugal,
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João Alexandrino, Fax: 1510 6438238, E-mail: jmalexan@berkeley.edu

Abstract

The study of hybrid zones resulting from Pleistocene vicariance is central in examining the potential of genetically diverged evolutionary units either to introgress and merge or to proceed with further isolation. The hybrid zone between two mitochondrial lineages of Chioglossa lusitanica is located near the Mondego River in Central Portugal. We used mitochondrial and nuclear diagnostic markers to conduct a formal statistical analysis of the Chioglossa hybrid zone in the context of tension zone theory. Key results are: (i) cline centres are not coincident for all markers, with average widths of ca. 2–15 km; (ii) heterozygote deficit was not observed across loci near the transect centre; (iii) associations of parental allele combinations (‘linkage disequilibrium’R) were not detected either across loci or across the transect. These observations suggest that the Chioglossa hybrid zone is not a tension zone with strong selection against hybrids but instead one shaped mostly by neutral mixing. The patterns uncovered suggest a complex history of populations over a small scale that may be common in southern Pleistocene refugia.

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