Description of two new species of Hymenagaricus (Agaricaceae, Basidiomycota) occurring on termite mounds in Dhofar, Southern Oman

Abstract Hymenagaricus is a group of small-sized, saprotrophic, veiled agaric, in the family Agaricaceae , with nearly 30 species, mainly distributed in paleotropical regions. The fruiting habit in Hymenagaricus is usually gregarious, occurring in large groups, on humus-rich soil, under forest trees. In this study, we reported two new species in the genus, namely, Hymenagaricus arabicae and H. lanosus , from Dhofar region, southern Oman. Both species are small-sized mushrooms, gregariously occurring on termite mounds. Hymenagaricus arabicae is characterized by a broadly umbonate center, which is covered with a smooth, dark-brown to blackish pellicle, composed of a hymeniform structure, with dark-brown to blackish and thick-walled veil elements. Hymenagaricus lanosus has small to slightly medium basidiomata, covered with whitish, woolly veil at the young stage; at the mature stage, the veil from the stem can easily be removed on handling and is characteristically noted for forked-shaped cheilocystidia. Species descriptions are based on morphological characterization of basidiomata and multigene phylogenetic analyses of internal transcribed spacer (ITS1-5.8S-ITS2 = ITS), D1/D2 domains of large subunit of nuclear ribosomal DNA (28S), and translation elongation factor one alpha ( EF-1α ) gene. Photographs of basidiomata, illustrations of microscopic features, and phylogenetic trees based on ITS and multigene sequence data are provided.