DICTYOMERIDIUM ¹

Gintaras Kantvilas ²

Dictyomeridium Aptroot, M.P.Nelsen & Lücking, in R. Lücking et al., Lichenologist 48: 756 (2016).

Type: D. proponens (Nyl.) Aptroot, M.P.Nelsen & Lücking

Thallus crustose, ecorticate. Photobiont Trentepohlia. Ascomata perithecia, conical to pyrifom, solitary or aggregated, erumpent or prominent and exposed, very rarely immersed, not in pseudostromata; perithecial wall black, in section completely carbonised, not differentiated internally. Ostiole eccentric. Interascal hyphae richly branched and anastomosed, not inspersed, embedded in a hyaline, non-amyloid, gelatinous matrix. Asci clavate to cylindrical, typically with a distinct ’tail’ or pedicel, 2–8-spored, non-amyloid, at maturity lacking an ocular chamber. Ascospores hyaline, ellipsoid to fusiform, muriform, smooth-walled, sometimes KI+ violet. Conidiomata pycnidia. Chemistry: some species contain lichexanthone.

A genus of eight, corticolous species, with three known for Australia, two of which are restricted to tropical Queensland. It has been separated from the related Polymeridium by the combination of an eccentric ostiole and muriform ascopsores, a distinction supported by DNA-sequence data. Together with Aptrootia, Bogoriella, Polymeridium and Pseudobogoriella, Dictyomeridium is classified in the Trypetheliaceae, a large, almost exclusively tropical, corticolous family that is very poorly represented in Tasmania.

Key references: Aptroot & Lücking (2016); Lücking et al. (2016); McCarthy & Kantvilas (2022).

1 Dictyomeridium tasmanicum P.M.McCarthy & Kantvilas

Austral. Lichenol. 90: 10 (2022). Type: Tasmania, near Triabunna, Spring Bay Mill, shoreline below ‘Lispers Corner’, 42°33’S 147°56’E, 2 m, on bark of Allocasuarina verticillata along foreshore, 20 November 2019, G. Kantvilas 429/19 (holo—HO!).

Thallus epiphloeodal, off-white to pale silvery grey, effuse, smooth to minutely uneven, 20–40 µm thick, to 25 mm wide; prothallus absent; photobiont cells sparse, 10–16 × 8–13 µm. Perithecia 0.25–0.45 mm wide, solitary, semi-immersed to almost superficial; ostiole eccentric to lateral, c. 20–40 µm wide. Interascal hyphae 0.5–0.7(–1) µm thick. Asci 2-spored, 84–115 × 15–25 µm. Ascospores 35–50–74 × 12–15–20 µm, ellipsoid to oblong, with 9–18 × 2–4 cuboidal or polygonal locules, usually constricted at the primary septum, with a smooth, hyaline perispore (2–)4–5(–7) µm thick. Pycnidia not seen.

Chemisty: nil.

Endemic to Tasmania and known only from the Spring Bay area where it occurs in fissures of coarse, deeply furrowed bark on she-oaks in coastal woodland. However, this species is so inconspicuous that it could easily be overlooked elsewhere, especially as it grew on patches of bark where virtually no other lichens were present.

Spring Bay Mill, ‘Lispers Corner’, 42°32’S 147°56’E, 10 m, 2021, G. Kantvilas 17/21 (HO).

References