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Graffenrieda emarginata (Melastomataceae) forms mycorrhizas with Glomeromycota and with a member of the Hymenoscyphus ericae aggregate in the organic soil of a neotropical mountain rain forest

Abstract:

Graffenrieda emarginata (Ruiz & Pav.) Triana (Melastomataceae) was found to be the most frequent tree on the nutrient-poor organic soil in a species-rich tropical mountain rain forest of southern Ecuador. Our studies revealed that the rootlets are symbiotically associated with arbuscular mycorrhizal fungi and simultaneously form ectomycorrhizas displaying a superficial Hartig net but no hyphal mantle. Molecular phylogeny revealed a multitude of previously unknown glomeromycete sequence types. Ultrastructure of the ectomycorrhiza-forming fungus indicated an ascomycete, and molecular phylogenetic studies identified the fungal symbiont as a new taxon within the Hymenoscyphus ericae (Read) Korf & Kernan aggregate (Ascomycota). The mycorrhizal state of G. emarginata is considered crucial for its competitiveness and abundance in these sites.