Diadema
Diadema Shoemaker & C.E. Babc., Can. J. Bot. 67(5): 1349 (1989).
Index Fungorum number: IF 25293; Facesoffungi number: FoF 08208, 8 morphological species (Species Fungorum 2022), no molecular data available.
Saprobic on culms of grasses (Poaceae). Sexual morph: Ascomata scattered, immersed, intra-epidermal, globose to subglobose, black to brown, smooth-walled and opening via a flat circular lid. Peridium 1-layered, composed of small pigmented thick-walled compressed cells, base composed of small pigmented thick-walled cells of textura angularis. Hamathecium of dense, numerous, septate, hyaline, cellular pseudoparaphyses. Asci 8-spored, numerous, bitunicate, fissitunicate, broadly-clavate, with a short orbicular pedicel, without an ocular chamber. Ascospores obliquely biseriate, broadly fusiform, usually cylindrical; frequently circular in section but narrowing to one end, brown to reddish-brown, 3-transseptate, without longitudinal septa, guttulate, smooth-walled or finely punctate, with wide, distinct mucilaginous sheath. Asexual morph: Unknown (adapted from Ariyawansa et al. 2014).
Type species: Diadema tetramerum Shoemaker & C.E. Babc.
Notes: Diadema is characterised by scattered, immersed ascomata, fissitunicate, broadly-clavate asci and broadly fusiform, usually cylindrical ascospores with a wide, distinct mucilaginous sheath. Ascomatal characters are significant in delineating species of Diadema (Shoemaker and Babcock 1989). Ariyawansa et al. (2014) re-examined the type specimen D. tetramerum from DAOM herbarium and considered other characters such as ascomata opening through a circular lid, asci with a short orbicular pedicel lacking an ocular chamber and trans-septate ascospores, lacking longitudinal septa, and surrounded by a very broad sheath, narrowed to a waist near the middle septum, as additional features in species delineation. Diadema is a distinct and type genus of Diademaceae but lacks sequence data. Fresh collections with DNA sequence data is needed to confirm the taxonomic placement of Diadema.
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