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A generalized heterozygote deficiency assessed with microsatellites in French common ash populations

Authors

  • M.-E. Morand,

    Corresponding author
    1. ENGREF, Laboratoire d’Ecologie, Systématique et Evolution (ESE), UPRESA CNRS 8079, Bâtiment 362, Université Paris-Sud, 91 405 Orsay Cedex, France,
      Marie-Elise Morand. Fax: 33 (0)1 69 15 73 53; E-mail: marie-elise.morand@ese.u-psud.fr
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  • S. Brachet,

    1. ENGREF, Laboratoire d’Ecologie, Systématique et Evolution (ESE), UPRESA CNRS 8079, Bâtiment 362, Université Paris-Sud, 91 405 Orsay Cedex, France,
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  • P. Rossignol,

    1. ENGREF, Laboratoire d’Ecologie, Systématique et Evolution (ESE), UPRESA CNRS 8079, Bâtiment 362, Université Paris-Sud, 91 405 Orsay Cedex, France,
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  • J. Dufour,

    1. INRA — Centre de Recherches d’Orléans, Unité Amélioration, Génétique et Physiologie forestières, BP 20619, 45 166 Olivet Cedex, France
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  • N. Frascaria-Lacoste

    1. ENGREF, Laboratoire d’Ecologie, Systématique et Evolution (ESE), UPRESA CNRS 8079, Bâtiment 362, Université Paris-Sud, 91 405 Orsay Cedex, France,
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Marie-Elise Morand. Fax: 33 (0)1 69 15 73 53; E-mail: marie-elise.morand@ese.u-psud.fr

Abstract

Common ash is a temperate forest tree with a colonizing behaviour, a discontinuous spatial distribution and a peculiar and poorly known mating system. Microsatellite markers were used to study the genetic structure in natural populations of common ash. Twelve populations located in northeastern France were analysed at five loci. Levels of genetic variability within and among stands were estimated for the seedling and adult stages. As expected for a forest tree, our results reveal high levels of intrapopulation diversity and a low genetic differentiation between stands. However, a general and significant heterozygote deficiency was found, with a mean FIS of 0.163 for the seedlings and of 0.292 for the adult trees. The different explanations for such an excess homozygosity are discussed: a nonMendelian inheritance of alleles, the presence of null alleles, a Wahlund effect and assortative mating.

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