Hysterangium atlanticum sp. nov., forms ectomycorrhizae with Coccoloba species (Polygonaceae) from the Atlantic rainforest of Northeastern Brazil

Hysterangium basidiomata were collected associated with Coccoloba alnifolia and C. laevis (Polygonaceae), in the Guaribas Biological Reserve in the Atlantic rainforest, of northeastern Brazil during the rainy seasons of 2012-2013. Based on its unique morphological and molecular traits, this new taxon is described as Hysterangium atlanticum sp. nov. The most prominent morphological characters that separate H. atlanticum from other close relatives are the large size of the basidiomata, the white peridium that rapidly turns greyish-orange to pale-red where bruised or exposed to air, and the ellipsoid to suboblong spores with a minutely verrucose surface. Molecular analyses of the LSU, SSU, atp6, and EF-1 alpha markers were done. The analyses of the concatenated atp6-EF-1 alpha matrix confirmed the placement of the new species in the /hysterangium lineage. Moreover, at the infra-generic level, Hysterangium atlanticum sp. nov. forms a sister clade with Hysterangium sp. from Dicymbe forests located in neighboring Guyana. Moreover, the ectomycorrhizae (EcM) formed by H. atlanticum and roots of Coccoloba species was confirmed, based on identical ITS nrDNA sequences obtained from basidiomata and EcM root tissues. The main conspicuous features of the EcM are: a well-developed plectenchimatous mantle, the ramarioid, abundant emanating hyphae with clamps and covered with crystals, the presence of oleoacanthocystidia, and the whitish rhizomorphs. This is the first report of a Hysterangium species forming EcM with native members of Coccoloba spp. in South America.