Polypyrenula
Polypyrenula D. Hawksw., Bull. Br. Mus. Nat. Hist., Bot. 14: 165 (1985).
Index Fungorum number: IF 25730; Facesoffungi number: FoF 08806, 1 morphological species (Species Fungorum 2022), 1 species with molecular data.
Lichenized on host. Thallus ecorticate, whitish to pale greyish or brownish. Photobiont (when present) Trentepohlia. Sexual morph: Ascomata dispersed, solitary, erumpent to prominent, black but basally covered by thin thallus layer, hemispherical to wart-shaped, carbonaceous, ostiolate, ostiole apical. Involucrellum well-developed, carbonaceous. Excipulum prosoplectenchymatous, basally reddish brown, laterally and apically thin and fused with involucrellum. Hamathecium comprising paraphysoids, hyaline, straight, branched and anastomosing, embedded in a gelatinous matrix. Asci (6–)8-spored, bitunicate, clavate, shortly pedicellate, with a non-amyloid ocular chamber. Ascospores biseriate, fusiform-ellipsoid and tapering towards the distal end, reddish brown but with basal cell paler, 5(−6)-septate, with distinct distosepta and rounded lumina except for the lowermost cell which is separated by a thin euseptum and has a triangular lumen, smooth-walled, not constricted at the septa, lacking a gelatinous sheath. Asexual morph: Pycnidia unknown. Chemistry: no substances detected by TLC (adapted from Hongsanan et al. 2020b).
Type species: Polypyrenula sexlocularis (Müll. Arg.) D. Hawksw.
Notes: Polypyrenula is characterised by dispersed, solitary, erumpent to prominent, black ascomata, clavate, shortly pedicellate asci and fusiform-ellipsoid 5(−6)-septate ascospores lacking a gelatinous sheath. Müller (1888) described Polypyrenula as having interascal anastomosing filaments. Hawksworth (1983) first provided a detailed description of Polypyrenula sexlocularis (as Polythelis sexlocularis) but could not describe the hamathecium as the specimen was limited. Hawksworth (1983) reported that the interascal filaments resembles the paraphyses of Pyrenula and accommodated the taxon in Pyrenulaceae. Harris (1989) and Aptroot (1991) considered the hamathecium to be rather cellular pseudoparaphyses and transferred Pyrenula to Requienellaceae. Harris (1995) restricted Requienellaceae to Requienella (Sordariomycetes) and transferred Polypyrenula to Pyrenulaceae. Miranda-González et al. (2020) reported that the hamathecium of P. sexlocularis reflects trabeculate pseudoparaphyses based on new collections from Mexico and transferred the taxon to Trypetheliaceae. Miranda-González et al. (2020) also demonstrated that the taxon is facultatively lichenized based on anatomical studies and the characters of the hamathecium corresponds to members of Dothideomycetes rather than Eurotiomycetes. In the phylogenetic analyses of Miranda-González et al. (2020) based on nuLSU and mtSSU, Polypyrenula clustered in an independent lineage in Trypetheliaceae outside the existing core genera. Miranda-González et al. (2020) also provided new data on the phorophyte associations of Polypyrenula and reinstated Polypyrenula sexlocularis as the correct name for this species. Polypyrenula resembles other basal lineages in Trypetheliaceae in having ecorticate thallus, exposed black perithecioid ascomata, euseptate spores that are not astrothelioid and weakly to non-lichenized thalli (Hyde et al. 2016, Lücking et al. 2016). Polypyrenula is unique in Trypetheliaceae in having pronounced eusepta together with distosepta. Miranda-González et al. (2020) provided ITS sequences of P. sexlocularis even though ITS is rarely use in Trypetheliaceae. The number of sequences available is very low for Trypetheliaceae. Polypyrenula has highly unique ascospores which explains its occurrence on very long branch with unresolved affinities among the basally diverging clades of Trypetheliaceae. Polypyrenula is morphologically and phylogenetically a distinct genus in Trypetheliaceae but the lineage lacks statistical support due to limited taxon sampling. More collections with sequence data are needed to establish the monophyly of the genus and confirm its relationship with other genera. Molecular markers available for P. sexlocularis include ITS, LSU and mtSSU.
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