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Extensive gene flow over Europe and possible speciation over Eurasia in the ectomycorrhizal basidiomycete Laccaria amethystina complex

Authors

  • LUCIE VINCENOT,

    1. UMR5175, Centre d’Ecologie Fonctionnelle et Evolutive, 1919 route de Mende, 34293 Montpellier Cedex 5, France
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    • Present address: Sustainable Agro-Ecosystems and Bioresources, Fondazione Edmund Mach-IASMA, via Edmund Mach 1, 38100 San Michele all’Adige, Italy

  • KAZUHIDE NARA,

    1. Department of Natural Environmental Studies, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8563, Japan
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  • CHRISTOPHER STHULTZ,

    1. UMR5175, Centre d’Ecologie Fonctionnelle et Evolutive, 1919 route de Mende, 34293 Montpellier Cedex 5, France
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  • JESSY LABBÉ,

    1. UMR1136, Interactions Arbres/Microorganismes, INRA-Nancy, 54280 Champenoux, France
    2. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6034, USA
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  • MARIE-PIERRE DUBOIS,

    1. UMR5175, Centre d’Ecologie Fonctionnelle et Evolutive, 1919 route de Mende, 34293 Montpellier Cedex 5, France
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  • LEHO TEDERSOO,

    1. Institute Ecology and Earth Sciences and The Natural History Museum, University of Tartu, 40 Lai Str., 51005 Tartu, Estonia
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  • FRANCIS MARTIN,

    1. UMR1136, Interactions Arbres/Microorganismes, INRA-Nancy, 54280 Champenoux, France
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  • MARC-ANDRÉ SELOSSE

    1. UMR5175, Centre d’Ecologie Fonctionnelle et Evolutive, 1919 route de Mende, 34293 Montpellier Cedex 5, France
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Lucie Vincenot, Fax: (+39 0461650872); E-mail: lucie.vincenot@cefe.cnrs.fr

Abstract

Biogeographical patterns and large-scale genetic structure have been little studied in ectomycorrhizal (EM) fungi, despite the ecological and economic importance of EM symbioses. We coupled population genetics and phylogenetic approaches to understand spatial structure in fungal populations on a continental scale. Using nine microsatellite markers, we characterized gene flow among 16 populations of the widespread EM basidiomycete Laccaria amethystina over Europe (i.e. over 2900 km). We also widened our scope to two additional populations from Japan (104 km away) and compared them with European populations through microsatellite markers and multilocus phylogenies, using three nuclear genes (NAR, G6PD and ribosomal DNA) and two mitochondrial ribosomal genes. European L. amethystina populations displayed limited differentiation (average FST = 0.041) and very weak isolation by distance (IBD). This panmictic European pattern may result from effective aerial dispersal of spores, high genetic diversity in populations and mutualistic interactions with multiple hosts that all facilitate migration. The multilocus phylogeny based on nuclear genes confirmed that Japanese and European specimens were closely related but clustered on a geographical basis. By using microsatellite markers, we found that Japanese populations were strongly differentiated from the European populations (FST = 0.416), more than expected by extrapolating the European pattern of IBD. Population structure analyses clearly separated the populations into two clusters, i.e. European and Japanese clusters. We discuss the possibility of IBD in a continuous population (considering some evidence for a ring species over the Northern Hemisphere) vs. an allopatric speciation over Eurasia, making L. amethystina a promising model of intercontinental species for future studies.

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