Geographic variation in algal partners of Cladonia subtenuis (Cladoniaceae) highlights the dynamic nature of a lichen symbiosis

Authors

  • Rebecca Yahr,

    1. Duke University, Department. of Biology, Box 90338, Durham, NC 27708 USA;
    2. Department of Botany, National Museum of Natural History, Smithsonian, Institution, PO Box 37012, Washington, DC 20013-7012 USA and Smithsonian Institution, Museum Conservation Institute, 4210 Silver Hill Road, Suitland, MD 20746 USA;
    3. Present address: Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UK.
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  • Rytas Vilgalys,

    1. Duke University, Department. of Biology, Box 90338, Durham, NC 27708 USA;
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  • Paula T. DePriest

    1. Department of Botany, National Museum of Natural History, Smithsonian, Institution, PO Box 37012, Washington, DC 20013-7012 USA and Smithsonian Institution, Museum Conservation Institute, 4210 Silver Hill Road, Suitland, MD 20746 USA;
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Errata

This article is corrected by:

  1. Errata: Corrigendum Volume 172, Issue 2, 377, Article first published online: 22 September 2006

Author for correspondence: Rebecca Yahr Tel: +44 131 248 2957 Fax: +44 131 248 2901 Email: r.yahr@rbge.nc.uk

Summary

  • • Multiple interacting factors may explain variation present in symbiotic associations, including fungal specificity, algal availability, mode of transmission and fungal selectivity. To separate these factors, we sampled the lichenized Cladonia subtenuis and associated Asterochloris algae across a broad geographic range.
  • • We sampled 87 thalli across 11 sites using sequence data to test for fungal specificity (phylogenetic range of association) and selectivity (frequency of association), fungal reproductive mode, and geographic structure among populations. Permutation tests were used to examine symbiont transmission.
  • • Four associated algal clades were found. Analysis of molecular variation (amova) and partial Mantel tests suggested that the frequency of associated algal genotypes was significantly different among sites and habitats, but at random with respect to fungal genotype and clade. The apparent specificity for Clade II algae in the fungal species as a whole did not scale down to further within-species lineage-dependent specificity for particular algae. Fungal genotypes were not structured according to site and appeared to be recombining.
  • • We suggest that ecological specialization exists for a specific lichen partnership and a site, and that this selectivity is dynamic and environment-dependent. We present a working model combining algal availability, fungal specificity and selectivity, which maintains variation in symbiotic composition across landscapes.

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