Chloroplast DNA variation and postglacial recolonization of common ash (Fraxinus excelsior L.) in Europe

Authors

  • M. HEUERTZ,

    1. Centre de Recherche Public-Gabriel Lippmann, CREBS Research Unit, 162 a, av. de la Faïencerie, L−1511 Luxembourg, Luxembourg;
    2. Université Libre de Bruxelles, Laboratoire de Génétique et Ecologie Végétales 1850, chée. de Wavre, Bruxelles B−1160, Belgium;
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    • Present address: Uppsala University, Institute of Ecology and Evolution, Department of Conservation Biology and Genetics, Norbyvägen 18D, Uppsala SE−75236, Sweden

  • S. FINESCHI,

    1. Istituto per la Protezione delle Piante, CNR, Via Madonna del Piano, Sesto Fiorentino (Firenze) I-50019, Italy;
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  • M. ANZIDEI,

    1. Istituto di Genetica Vegetale, CNR, Via Madonna del Piano, Sesto Fiorentino (Firenze) I-50019, Italy;
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  • R. PASTORELLI,

    1. Istituto di Genetica Vegetale, CNR, Via Madonna del Piano, Sesto Fiorentino (Firenze) I-50019, Italy;
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  • D. SALVINI,

    1. Istituto per la Protezione delle Piante, CNR, Via Madonna del Piano, Sesto Fiorentino (Firenze) I-50019, Italy;
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  • L. PAULE,

    1. Technical University, Faculty of Forestry, Ul. T.G. Masaryka 2117/24, Zvolen SK−96053, Slovakia;
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  • N. FRASCARIA-LACOSTE,

    1. ENGREF, Laboratoire Ecologie, Systématique et Evolution, UMR CNRS-ENGREF n. 8079, Bâtiment 360, Université Paris-XI, Orsay F−91405, France;
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  • O. J. HARDY,

    1. Université Libre de Bruxelles, Laboratoire de Génétique et Ecologie Végétales 1850, chée. de Wavre, Bruxelles B−1160, Belgium;
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  • X. VEKEMANS,

    1. Université de Lille 1, Laboratoire de Génétique et Evolution des Populations Végétales, UMR CNRS 8016 — FR CNRS 1818, Villeneuve d’Ascq cedex F−59655, France
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  • G. G. VENDRAMIN

    Corresponding author
    1. Istituto di Genetica Vegetale, CNR, Via Madonna del Piano, Sesto Fiorentino (Firenze) I-50019, Italy;
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Giovanni G. Vendramin. Fax: +39 055 5225729; E-mail: giovanni.vendramin@igv.cnr.it.

Abstract

We used chloroplast polymerase chain reaction-restriction-fragment length polymorphism (PCR-RFLP) and chloroplast microsatellites to assess the structure of genetic variation and postglacial history across the entire natural range of the common ash (Fraxinus excelsior L.), a broad-leaved wind-pollinated and wind-dispersed European forest tree. A low level of polymorphism was observed, with only 12 haplotypes at four polymorphic microsatellites in 201 populations, and two PCR-RFLP haplotypes in a subset of 62 populations. The clear geographical pattern displayed by the five most common haplotypes was in agreement with glacial refugia for ash being located in Iberia, Italy, the eastern Alps and the Balkan Peninsula, as had been suggested from fossil pollen data. A low chloroplast DNA mutation rate, a low effective population size in glacial refugia related to ash's life history traits, as well as features of postglacial expansion were put forward to explain the low level of polymorphism. Differentiation among populations was high (GST = 0.89), reflecting poor mixing among recolonizing lineages. Therefore, the responsible factor for the highly homogeneous genetic pattern previously identified at nuclear microsatellites throughout western and central Europe (Heuertz et al. 2004) must have been efficient postglacial pollen flow. Further comparison of variation patterns at both marker systems revealed that nuclear microsatellites identified complex differentiation patterns in south-eastern Europe which remained undetected with chloroplast microsatellites. The results suggest that data from different markers should be combined in order to capture the most important genetic patterns in a species.

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