Proceedings of the Royal Society of London, Biological Sciences
2003: 270(1517): 835-842 .

Specialized cheating of the ectomycorrhizal symbiosis by an epiparasitic liverwort

Bidartondo, M.I.1, Bruns, T.D.1, Weiss, M.2, Sergio, C.3 and D.J. Read4
1 Department of Plant & Microbial Biology, University of California, Berkeley, California 94720-3102, USA
2 Spezielle Botanik und Mykologie, Universität Tübingen, D-72076 Tübingen, Germany
3 Museu e Jardim Botânico, CEBV, 1250-102 Lisboa, Portugal
4 Department of Animal & Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK

Summary
Hundreds of non-photosynthetic vascular plants in 10 diverse families obtain all of their carbon from fungi, but in most cases the fungi and the ultimate sources of carbon are unknown. In a few cases, such plants have been shown to be epiparasitic because they obtain carbon from neighboring green plants via shared mycorrhizal fungi. In all such cases, the epiparasitic plants have been found to specialize upon narrow lineages of ecto- or arbuscular mycorrhizal fungi. Here we show that a non-vascular plant, the non-photosynthetic liverwort Cryptothallus mirabilis, is epiparasitic and is specialized on Tulasnella species that form ectomycorrhizae with surrounding trees at four locations in England, France and Portugal. Using microcosm experiments we show the interaction with Tulasnella is necessary for growth of Cryptothallus, and using labeling experiments we show that 14CO2 provided to birch seedlings is transferred to Cryptothallus via Tulasnella. This is one of the first documented cases of epiparasitism by a non-vascular plant and of ectomycorrhizal formation by Tulasnella. These results broaden the emerging association between epiparasitism and mycorrhizal specialization into a new class of plants and a new order of fungi.

Keywords: symbiosis, parasitism, mutualism, cheating, mycorrhizae.


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