Clypeococcum
Clypeococcum D. Hawksw., Bot. J. Linn. Soc. 75: 196 (1977).
Index Fungorum number: IF 1114; Facesoffungi number: FoF 08783, 9 morphological species (Species Fungorum 2022), 2 species with molecular data.
Lichenicolous. Sexual morph: Pseudothecia immersed to semi-immersed under a black clypeus, visible as rounded or patch-like spots on the lichen thallus, clustered, rarely scattered, globose to subglobose, or ovoid, dark brown to black, ostiole central, discrete to gaping, with porelike opening. Peridium thin-walled, composed of 1–3 layers of brown to dark brown, pseudoparenchymatous cells, arranged in a textura angularis. Hamathecium composed of dense, filiform, branched, distinct septate, anastomosed, pseudoparaphyses, embedded in a hyaline gelatinous matrix. Asci 8-spored, bitunicate, ovoid to subcylindrical, usually short-pedicellate, apically rounded and thickened, with rounded ocular chamber. Ascospores overlapping 1–3-seriate, hyaline when young, becoming brown to dark brown when mature, ellipsoidal to fusiform, with rounded apex, uniseptate, constricted at septum, rough-walled, minutely verruculose. Asexual morph: Unknown (adapted from Doilom et al. 2018).
Type species: Clypeococcum cladonema (Wedd.) D. Hawksw.
Notes: Clypeococcum is characterised by immersed to semi-immersed pseudothecia, ovoid to subcylindrical asci and ellipsoidal to fusiform, uniseptate ascospores with a rounded apex. Clypeococcum cladonema was previously known as Lecidea cladonema, found as a parasite of Parmelia delisei by Weddell (1874). Clypeococcum resembles Polycoccum but differs in having pseudothecial walls comprising textura intricata which are thick around the ostiole and pseudothecia developing in a common clypeus while Polycoccum has clear pseudothecial walls and the pseudothecia are produced on the host thallus with a tendency to induce galls (Ertz et al. 2015). Some authors have treated Clypeococcum in Dacampiaceae (Lumbsch & Huhndorf 2010, Hyde et al. 2013, Wijayawardene et al. 2014, 2018, Pirogov 2015, Jaklitsch et al. 2016). Ertz et al. (2015) provided sequence data for C. placopsiiphilum and C. psoromatis and accommodated Clypeococcum in a new family Polycoccaceae (Trypetheliales, Dothideomycetes) based on phylogenetic analyses of LSU sequence data. Ertz et al. (2015) reported that there are very few morphological characters for generic delineation in Polycoccaceae owing to the long branches in their phylogenetic tree which he explained as ‘fast-evolving contrasting with low morphological variability’. The type species, C. cladonema differs from other species in Clypeococcum in having smaller ascospores, 8-spored asci and pseudothecia immersed in patch-like clypeus. Hawksworth (1977) re-examined the type specimen of C. cladonema and placed Clypeococcum in Pleosporaceae (Pleosporales) based on morphology of hyphal-like pseudothecial walls (textura intricata), turning pseudoparenchymatous at maturity, with subcylindrical, short-pedicellate asci. Doilom et al. (2018) examined the isotype of C. cladonema (S-F9606) and reported that it forms pseudothecial walls comprising textura angularis, pseudoparenchymatous cells, with subcylindrical to ovoid asci. Zhurbenko (2020) added C. lenae based on morphology namely immersed, aggregated pseudothecia, united by a common, K+ violet clypeus, and frequently laterally and basally surrounded by stromatically transformed host tissues, I and K/I− hymenium, well-developed pseudoparaphyses, bitunicate, 8-spored, I and K/I− asci, and brown, ellipsoid to obovate, muriform ascospores. Clypeococcum is a distinct genus in Polycoccaceae but the type species must be sequenced to confirm this taxonomic placement.
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