Mycoporum Flot. ex Nyl., Mém. Soc. Imp. Sci. Nat. Cherbourg 3: 186 (1855).
Index Fungorum number: IF 3337; Facesoffungi number: FoF 08310, 12 morphological species (Species Fungorum 2021), 6 species with molecular data.
Saprobic on growing bark of trees or stems. Sexual morph: Ascomata semi immersed to superficial on host surface, simple, visible as dark brown to black circle on host surface. Peridium thick-walled, composed of several layers of dark-brown cells of textura angularis. Hamathecium present, with cellular pseudoparaphyses, anastomosing, branching, embedded in mucilaginous matrix, sometimes aparaphysate, covering asci by gelatinous matrix. Asci bitunicate, fissitunicate, 8-spored, ovoid to saccate, sessile with indistinct ocular chamber, thick-walled. Ascospores bi-to tri-seriated, or overlapping, oblong to cylindrical or ellipsoid, hyaline to subhyaline multi-septate, very slightly constricted at the septum, smooth or rough-walled. Asexual morph: Undetermined.
Type species: Mycoporum elabens (A. Massal.) Flot. ex Nyl.
Notes: Mycoporum was introduced by Flot. ex Nylander with M. elabens as type species. Mycoporum is characterized by semi immersed to superficial ascomata, ovoid to saccate asci with sessile and indistinct ocular chamber, oblong to cylindrical or ellipsoid, hyaline to subhyaline multi-septate ascospores slightly constricted at the septum, smooth to rough-walled. Harris (1973) and Poelt (1969) re-studied the type species of Mycoporum, M. elabens and considered it as non-lichenized. Eriksson (1981) observed an old material and could not see any algal cells near the ascomata or in the surrounding mycelium and suggested that Mycoporum might be related to Arthopyreniaceae. Eriksson (1981) accepted two species in Mycoporum; M. elabens and M. pycnocarpum Nyl. Harris (1995) mentioned the occurrence of algae on some Mycoporum samples, and pointed out that the identity of the algae was mysterious as they were not part of algal genera that usually occur in lichen thalli. Harris (1995, p. 61) described the hamathecium in Mycoporum as irregular, to some extent gelatinizing and disarticulating physes which are often hidden by irregular oil droplets. Lumbsch (1999) agreed with Harris (1973) and Poelt (1969) and mentioned Mycoporum as being non-lichenized with algal cells occurring in the surroundings of the ascomata having no close contact with the fungal hyphae. Lumbsch (1999) considered the taxonomic placement of Mycoporum within Dothideomycetes, especially Dothideales is doubtful. Lumbsch (1999) mentioned that the ascomata of M. elabens are not perithecioid and there is no difference in development of the hamathecium in M. elabens compared to Arthothelium spectabile even though those of M. elabens is termed as pseudoparaphyses and those of Arthothelium spectabile are paraphysoids. Lumbsch (1999) re-examined some specimens not conspecific with the type and suggested that there may be two separate lineages in Dothideomycetes and Arthoniomycetes, and M. elabens is a representative of Arthoniomycetes. Mycoporum elabens differs from Arthonia susa in asci characters in that the former has shallow ocular chamber and amyloid ring structure while the latter has long and narrow ocular chamber with no amyloid structures (Lumbsch 1999; Lendemer et al. 2013; Thiyagaraja et al. 2020). Both ascus types are characters of members of Arthoniales. Harris (1995) and Aptroot et al. (2008) added several species to Mycoporum but without molecular data. Hyde et al. (2013) included Mycoporum in Mycoporaceae, Dothideomycetidae incertae sedis. Hametner et al. (2014) provided sequence data for Mycoporum sparsellum and in their phylogenetic analysis based on SSU and rbcL, M. sparsellum clustered with Acrocordia gemmate sister to Trentepohlia abietina but the result was inconclusive due to limited gene region and low taxon sampling. Liu et al. (2017) did not consider Mycoporum in their analysis due to lack of molecular data. Wijayawardene et al. (2017) accommodated Mycoporum and the family Mycoporaceae in Pleosporales. Park et al. (2017) separated Mycoporum from Arthonia species in being “pyrenocarpous” and having pseudoparaphyses. Thiyagaraja et al. (2021) suggested that the diagnostic character of hamathecium amyloidity, ascus type and ascospore pigmentation might be uncertain to differentiate Mycoporum species from similar taxa or there is probably mix-up of unrelated taxa. Mycoporum is currently a distinct genus in Mycoporaceae, Pleosporales. Members of Mycoporum needs revision as only six species have molecular data and several taxa presently placed in Mycoporum might belong to Arthoniomycetes. Molecular markers available for Mycoporum are ITS, SSU and rbcL. In this study, we illustrate Mycoporum with a specimen of Mycoporum populnellum (F216647).