Nature 379, 63 - 66 (04 January 1996); doi:10.1038/379063a0

Evolution of extreme specialization within a lineage of ectomycorrhizal epiparasites

K. W. Cullings^*, T. M. Szaro & T. D. Bruns

Department of Environmental Science, Policy, and Management, University of California, Berkeley, California 94720 USA
^*Present address Department of Biology, San Francisco State University, California 94132, USA

MONOTROPES (Monotropoideae, Ericaceae) are achlorophyllous, epiparasitic plants that receive all of their fixed carbon from green plants through a common ectomycorrhizal association rather than by a direct parasitic connection (Fig. 1)^1,2. Using molecular identification methods we show that some monotropes are highly specific in their fungal associations and at least one species, Pterosporo andromedea is specialized on a single species group within the genus Rhizopogon. Phylogenetic analysis of the Monotropoideae shows that specialization has been derived through narrowing of fungal associations within the lineage containing P. andromedea. High specificity is contrary to past predictions for the Monotropoideae and for plant communities in general, raising many questions about the roles of mycorrhizal specificity in ecosystem function.

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