Trypethelium
Trypethelium Spreng., Anleit. Kennt. Gew. 3: 350 (1804).
Index Fungorum number: IF 5628; Facesoffungi number: FoF 08785, 16 morphological species (Species Fungorum 2022), 6 species with molecular data.
Lichenized on bark in terrestrial, lowland to lower montane tropical habitats. Thallus corticate, yellow-brown to olive-green. Photobiont Trentepohlia. Sexual morph: Ascomata aggregated in pseudostromata, sessile, brown-black or covered by algal-free, sterile tissue filled with crystalline, yellow to orange, KOH+ red to purple pigment, globose, coriaceous to carbonaceous, ostiolate, ostiole round. Excipulum prosoplectenchymatous, dark brown to brown-black. Hamathecium comprising paraphysoids, hyaline, straight, branched and anastomosing, embedded in a thick, gelatinous matrix. Asci 8-spored, bitunicate, fissitunicate, obclavate, short pedicellate, with refractive ring and nonamyloid ocular chamber. Ascospores irregularly arranged to biseriate, fusiform, hyaline, multi-septate, with thin distosepta and more or less rectangular lumina, smooth-walled, not constricted at the septa, surrounded by an evanescent mucilaginous sheath. Asexual morph: Unknown. Chemistry: Yellow to orange or red anthraquinones and perylenequinones produced in the pseudostromata (adapted from Hyde et al. 2013, Aptroot & Lücking 2016).
Type species: Trypethelium eluteriae Spreng.
Notes: Trypethelium is characterised by sessile, brown-black ascomata, obclavate, short pedicellate asci with refractive ring and nonamyloid ocular chamber, and fusiform, hyaline, multiseptateascospores with thin distosepta surrounded by an evanescent mucilaginous sheath. In the phylogenetic analysis of Nelsen et al. (2014) and Lücking et al. (2016), the type species T. eluteriae does not cluster with other species classified under this name such as T. nitidiusculum, T. ochroleucum and T. tropicum which are now transferred to Astrothelium and Nigrovothelium. Trypethelium sensu stricto forms a monophyletic group and is characterised by distinct pseudostromatic ascomata packed with or enclosed with anthraquinone crystals, hyaline, multiseptate, transversely septate ascospores with thin septa and rectangular lumina when matured (Harris 1995). Trypethelium differs from Polymeridium in having ecorticate, whitish thallus and solitary, exposed ascomata. Trypethelium differs from Bathelium in that the latter has bare, brown-black pseudostromata with limited ascomata which does not occur in members of Trypethelium. Trypethelium differs from Viridothelium in having prominent to sessile pseudostromata while Viridothelium has immersed-erumpent and solitary ascomata. Conventionally, Trypethelium comprised species with thallus-dominated perithecia with distinct, apical ostioles and transversely septate ascospores (Hyde et al. 2013). Trypethelium, in its strict sense is limited to species with pseudostromatic perithecia, that usually comprise yellow to orange, crystalline pigments, and multiseptateascospores with more or less thin septa and walls and rectangular lumina (Aptroot & Lücking 2016). Makhija and Patwardhan (1993) applied an ascomatal grouping system to Trypethelium which was previously used to delimit infrageneric groups in Laurera and reported twelve pseudostromal types in Trypethelium species from India emphasizing the presence of variable pseudostromal types within Trypethelium. In the phylogenetic analyses of Nelsen et al. (2014), species producing the T. eluteriae- and T. subeluteriae types of pseudostroma were reported in the Trypethelium s. str. clade. The T. eluteriae-type pseudostroma is distinct from the thallus in lacking cortical algal and medullary strata and a cortical deposit is formed below the pseudostroma and ascomata are enclosed in one-layer comprising hyaline or filled with yellow to orange crystals (Makhija & Patwardhan 1993). The T. subeluteriae-type pseudostroma consists of a cortical layer below the pseudostroma and above it (Makhija & Patwardhan 1993). Nelsen et al. (2014) reported that Trypethelium is polyphyletic based on a detailed genus-level phylogeny using mtSSU and nuLSU sequence data. Nelsen et al. (2014) also mentioned that patterns of ascospore septation, ostiole location and type of ascomatal collection is not useful for the delimitation of Trypethelium from other genera in Trypetheliaceae. Trypethelium sensu stricto forms a sister clade to the Marcelaria purpurina group (Nelsen et al. 2014). Luangsuphabool et al. (2016) studied the diversity of Trypethelium eluteriae group in Thailand using molecular (ITS and mtSSU rDNA sequences), morphological, and chemical data and reported that T. eluteriae was not homogeneous and comprised greater diversity. Luangsuphabool et al. (2016) identified three species T. eluteriae, T. platystomum and T. subeluteriae and reported that the three species have different chemical profiles but the ascospore size overlap among them. Aptroot and Lücking (2016) provided an updated account of Trypethelium and accepted 16 species. Trypethelium is morphologically and phylogenetically a distinct and type genus of Trypetheliaceae. Molecular markers available for Trypethelium species include LSU, ITS, TEF-1, RPB2 and mtSSU.
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