Anisomeridium (Müll. Arg.) M. Choisy, Icon Lich Univ 1: 24 (1928).
MycoBank number: MB 201; Index Fungorum number: IF 201; Facesoffungi number: FoF 08073; approximately 60 morphologically defined species (this paper; Harada 2019), molecular data thus far available for four species.
≡ Arthopyrenia sect. Anisomeridium Müll. Arg., Flora 66: 290 (1883)
MycoBank number: MB 700075; Index Fungorum number: IF 700075; Facesoffungi number: FoF 08852.
Lichenized on bark or more rarely on leaves or rocks, possibly lichenicolous; in lowland to montane tropical to subtropical habitats, with few species extending into temperate regions. Thallus usually ecorticate or sometimes with thin cortex, white or shades of grey-green to green. Photobiont Trentepohlia. Ascomata scattered or rarely clustered, erumpent to sessile, mostly black, carbonaceous, ostiolate, ostiole apical or lateral. Involucrellum present or reduced, carbonized. Excipulum dense, consisting of compressed hyphae, appearing prosoplectenchymatous in thin, bleached sections, hyaline to brown or brown-black. Hamathecium comprising 0.5–0.7 µm wide paraphyses, hyaline, straight, branched and anastomosing. Asci (2–)8-spored, bitunicate, fissitunicate, cylindrical, short pedicellate, with narrow, non- amyloid ocular chamber and fluorescent cap- or ring-structures. Ascospores uni- or biseriate to irregularly arranged, ellipsoid-oval to broadly fusiform, small to medium-sized [(10–)15–45(–55) × 4.5–15(–20) µm], hyaline to very rarely brown, 1(–3)-septate, with thin eusepta and rectangular lumina, smooth-walled or granular ornamented, sometimes slightly constricted at the septa, in 1-septate ascospores the upper cell often distinctly larger than the lower cell (very rarely the opposite). Pycnidia common, immersed to sessile, visible as black dots but sometimes conspicuous and flask- shaped. Conidia acrogenous, either macro- or microconidia; macroconidia usually aseptate, (globose to) broadly ellipsoid to bacillar, (2.5–)5–15(–45) × (2–)3–7(–16) µm large, hyaline, often forming clusters embedded in a gelatinous matrix, these clusters in some species in the form of sacci or cirri; microconidia aseptate, globose to broadly ellipsoid or fusiform, small, 2–4(–5) × 1–2(–4) µm large, hyaline.
Chemistry: Most species do not contain secondary substances; lichexanthone present in some taxa.
Type species: Arthopyrenia xylogena Müll.Arg., Flora 66: 290 (1883) [= Anisomeridium subnectendum (Nyl.) R.C.Harris, More Florida Lichens: 150 (1995)].
Notes: Lücking et al. (in Hyde et al. 2013) did not treat this genus in detail. Citing Riedl (1963), Harris (1995) considered Arthopyrenia xylogena Müll. Arg. the ‘lectotype’ of the genus. However, Müller (1883) only included a single species in Arthopyrenia sect. Anisomeridium, viz. Arthopyrenia xylogena, which is then by default the (holo-) type (although the terms ‘holo-’ and ‘lectotype’ technically do not apply to names above species [ICN Art. 10.1, Note 1]. Riedl’s (1963: 270) statement that “… xylogena muss als Typusart der Sektion Anisomeridium Müll. Arg. betrachtet werden.” [“… xylogena is to be considered the type species of section Anisomeridium Müll. Arg.”] refers to the differences between Müller’s protologue of the species description and the features observed by Riedl himself, casting doubt as to Müller properly described the taxon at hand. However, this only affects typification of the species itself, not typification of the genus, which is fixed by the single species name listed in the protologue.
The taxonomic delimitation between Anisomeridium and Megalotremis is elaborated in detail below under the latter genus (see below). Lücking et al. (2017) gave the number of species in Anisomeridium as 200, but revision of published literature revealed that only 57 species are currently to be accepted in the genus, after transferral of several taxa to Megalotremis (see below).