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 ectomy corrhizas 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 Hymenoscy phus ericae (Read) Korf & Kernan aggregate (Ascomycota). The mycorrhizal state of G. emarginata is considered crucial for its competitiveness and abundance in these sites.Key words: arbuscular mycorrhiza, ectomycorrhiza, Glomeromycota, Hymenoscyphus ericae aggregate, neotropical mountain rain forest, Ecuador.

The tropical mountain forest

“…In total, 112 tree species belonging to 40 different families were found to form arbuscular mycorrhizas (Kottke & Haug 2004). Fourteen morphotypes of arbuscular mycorrhizas corresponding to the three main groups of Glomeromycota (Glomeraceae, Gigasporaceae Acaulosporaceae) were detected on one single tree species, Alzatea verticillata (Alzateaceae; Beck et al 2007).…”

“…Three species (two of Neea and one of Guapira) belong to Nyctaginaceae, a family known to form ectomycorrhizas in tropical forests of South America (Alexander & Högberg 1986, Moyersoen 1993. Graffenrieda emarginata, however, was the first member of Melastomataceae shown to form ECM and simultaneously also AM (Haug et al 2004). Sections through the mycorrhizas revealed Glomeromycota in the inner cortical layer, and an Ascomycete forming a thin hyphal sheath (Fig.…”

“…DNA sequences of the Ascomycete clustered within the Rhizoscyphus (=Hymenoscyphus) ericae aggr. (Haug et al 2004), a group of fungi forming ericoid . Although experimental proof is lacking, we speculate that G. emarginata is supported by this Ascomycete in a similar way as shown for the ericads.…”

“…However, no information was available on their mycorrhizal state and involved fungi in the tropical mountain rainforest. A first inventory of the mycorrhizal state of a large number of trees, terrestrial and hemiepiphytic ericads, as well as some epiphytic orchids in the RBSF revealed persistently well developed mycorrhizas (Kottke et al 2004, Setaro et al 2006a, Suarez et al 2006. Morpho-typing and sequencing of the mycorrhizal fungi directly from the mycorrhizas revealed distinct associations for trees (mainly arbuscular mycorrhizas/AM, rarely ectomycorrhizas/ECM), ericads (cavendishioid mycorrhizas/CM for Andean ericads, ericoid mycorrhizas/ERM for non-Andean ericads) and pleurothallid orchids (orchid mycorrhizas/OM) (Kottke et al 2008a).…”

Placing an Omnivore in a Complex Food Web: Dietary Contributions to Adult Biomass of an Ant1

“…Samples were dried at 60°C for 24 hr, weighed, and stored in a desiccator until analysis (n = 2-5 replicates Limits between the different trophic levels were calculated in relation to the δ 15 N signature of a baseline, Graffenrieda emarginata (Ruiz & Pav.) Triana (Melastomataceae), one of the most frequent trees on the nutrient-poor soil in southern Ecuador (Haug et al 2004;Illig et al 2005). We assumed that two trophic levels were separated by a difference of ~3.4‰ δ 15 N due to fractionation (Post 2002;Maraun et al 2011).…”