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European phylogeography of the epiphytic lichen fungus Lobaria pulmonaria and its green algal symbiont

Authors

  • Ivo Widmer,

    Corresponding author
    • WSL Swiss Federal Research Institute, Birmensdorf, Switzerland
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    • These authors contributed equally to this work and are considered joint first authors.
  • Francesco Dal Grande,

    1. WSL Swiss Federal Research Institute, Birmensdorf, Switzerland
    Current affiliation:
    1. Biodiversity and Climate Research Centre (BiK-F), Senckenberg Gesellschaft fuer Naturforschung, Frankfurt am Main, Germany
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    • These authors contributed equally to this work and are considered joint first authors.
  • Laurent Excoffier,

    1. Computational and Molecular Population Genetics Laboratory, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
    2. Swiss Institute of Bioinformatics, Quartier Sorge – Batiment Genopode, Lausanne, Switzerland
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  • Rolf Holderegger,

    1. WSL Swiss Federal Research Institute, Birmensdorf, Switzerland
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  • Christine Keller,

    1. WSL Swiss Federal Research Institute, Birmensdorf, Switzerland
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  • Vladimir S. Mikryukov,

    1. Laboratory of Population and Community Ecotoxicology, Institute of Plant and Animal Ecology, Ural Branch, Russian Academy of Sciences, Ekaterinburg, Russia
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  • Christoph Scheidegger

    1. WSL Swiss Federal Research Institute, Birmensdorf, Switzerland
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Correspondence: Ivo Widmer, Laboratory of Geographical Information Systems (LASIG), École Polytechnique Fédérale de Lausanne (EPFL), Station 18, Lausanne, CH-1015, Switzerland. Fax: +41 21 693 57 90; E-mail: ivo.widmer@epfl.ch

Abstract

In lichen symbiosis, fungal and algal partners form close associations, often codispersed by vegetative propagules. Due to the particular interdependence, processes such as colonization, dispersal or genetic drift are expected to result in congruent patterns of genetic structure in the symbionts. To study the population structure of an obligate symbiotic system in Europe, we genotyped the fungal and algal symbionts of the epiphytic lichen Lobaria pulmonaria at eight and seven microsatellite loci, respectively, and analysed about 4300 L. pulmonaria thalli from 142 populations from the species' European distribution range. Based on a centroid approach, which localizes centres of genetic differentiation with a high frequency of geographically restricted alleles, we identified the South Italy–Balkan region as the primary glacial refugial area of the lichen symbiosis. Procrustean rotation analysis and a distance congruence test between the fungal and algal population graphs indicated general concordance between the phylogeographies of the symbionts. The incongruent patterns found in areas of postglacial recolonization may show the presence of an additional refugial area for the fungal symbiont, and the impact that horizontal photobiont transmission and different mutation rates of the symbionts have on their genotypic associations at a continental scale.

Ancillary