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Genetic diversity in Tetrachaetum elegans, a mitosporic aquatic fungus

Authors

  • Beryl Laitung,

    Corresponding author
    1. UMR 5172 Laboratoire Dynamique de la Biodiversité, Centre National de la Recherche Scientifique, 29 rue Jeanne Marvig, 31055 Toulouse cedex 4, France,
      Beryl Laitung. Present address: Unité de Génétique et d’Amélioration des Plantes Fourragères, Institut National de la Recherche Agronomique, Centre de Recherche de Poitou-Charentes, Route de Saintes, 86600 Lusignan, France. Fax: + 33 549 556 044; E-mail: laitung@lusignan.inra.fr
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  • Eric Chauvet,

    1. UMR 5172 Laboratoire Dynamique de la Biodiversité, Centre National de la Recherche Scientifique, 29 rue Jeanne Marvig, 31055 Toulouse cedex 4, France,
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  • Nicolas Feau,

    1. Centre de Recherche en Biologie Forestière, Université Laval, Sainte-Foy (QC), Canada G1K 7P4,
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  • Katia Fève,

    1. Laboratoire de Génétique Cellulaire, Institut National de la Recherche Agronomique, BP 27, 31326 Castanet-Tolosan cedex, France,
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  • Lounès Chikhi,

    1. UMR 5174 Evolution et Diversité Biologique, Université Toulouse III — Paul Sabatier, 118 route de Narbonne, 31062 Toulouse cedex 4, France
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  • Monique Gardes

    1. UMR 5174 Evolution et Diversité Biologique, Université Toulouse III — Paul Sabatier, 118 route de Narbonne, 31062 Toulouse cedex 4, France
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Beryl Laitung. Present address: Unité de Génétique et d’Amélioration des Plantes Fourragères, Institut National de la Recherche Agronomique, Centre de Recherche de Poitou-Charentes, Route de Saintes, 86600 Lusignan, France. Fax: + 33 549 556 044; E-mail: laitung@lusignan.inra.fr

Abstract

Tetrachaetum elegans Ingold is a saprobic aquatic hyphomycete for which no sexual stage has yet been described. It occurs most commonly during the initial decay of tree leaves in temperate freshwater habitats and typically sporulates under water. Dispersal of the aquatic fungus takes place primarily in the water column and has a large passive component. Differences in substrate composition (e.g. quality of leaf litter) may also play a role in the distribution of different species or genotypes. The population genetic structure of T. elegans was studied using amplified fragment length polymorphism (AFLP) multilocus fingerprints. The populations were isolated from the leaf litter of three different tree genera, sampled in nine streams distributed throughout a mixed deciduous forest. Molecular markers were developed for 97 monosporic isolates using four selective primer pairs. A total of 247 fragments were scored, of which only 32 were polymorphic. Significant stream differentiation was detected for the isolates considered in this study. Analysis of molecular variance revealed that 20% of the genetic variation observed was the result of differences between streams. No correlation between genetic and geographical distances was found but a few multilocus genotypes were observed in different locations. Altogether these results suggest that environmental barriers play a role in the population structure of this aquatic fungus. No clear-cut effect of leaf litter composition on genetic variation could be demonstrated. Finally, tests of linkage disequilibrium between the 32 polymorphic AFLP loci as well as simulations did not provide a final answer regarding clonality in T. elegans. Indeed, it was possible to reject linkage equilibrium at different sampling levels and show that full linkage was unlikely.

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