HALEGRAPHA ¹

Gintaras Kantvilas ²

Halegrapha Rivas Plata & Lücking, in R. Lücking et al., Lichenologist 43: 333 (2011).

Type: H. chimaera Rivas Plata & Lücking

Thallus crustose, corticate, containing abundant calcium oxalate crystals. Photobiont Trentepohlia, with cells ellipsoid to subglobose, 12–18 × 7–12 µm, scattered or clustered. Ascomata apothecia, lirelliform, black, immersed to erumpent, with or without a lateral thalline margin. Disc usually concealed. Proper exciple black, entire, rarely striate, in section apically or entirely carbonised and opaque, K–. Hypothecium hyaline to pale yellowish. Hymenium hyaline, I+ yellow-brown, KI–, usually inspersed with oil droplets. Asci elongate-clavate, 8-spored, of the Graphis-type: non-amyloid, with a slightly thickened apex and ± truncate ascoplasm. Paraphyses simple, straight and parallel; apices hyaline, not expanded. Ascospores fusiform, with rounded or tapered apices, transversely septate, non-halonate, hyaline when young, becoming grey-brown, I+, KI+ reddish purple at the septa; locules lens-shaped. Conidiomata unknown. Chemistry: depsidones, especially stictic or norstictic acids, or nil.

A genus of six corticolous species, five of which are tropical and one occuring in Australasia, including Tasmania. Anatomically and morphologically, Halegrapha is intermediate between Graphis and Phaeographis, and its distinct but enigmatic position has been established by molecular methods. It combines a whitish grey thallus containing calcium oxalate and a thick, carbonised exciple that conceals the apothecial disc (as seen in Graphis) with an inspersed hymenium and brown ascospores (as in Phaeographis).

Key references: Archer (2006); Lücking et al. (2011).

1 Halegrapha mucronata (Stirt.) Lücking

In R. Lücking et al., Lichenologist 43: 340 (2011); —Graphis mucronata Stirt., Trans. Glasgow Field Nat. 4: 95 (1876); Phaeographis mucronata (Stirt.) Zahlbr., Cat. Lich. Univ. 2: 382 (1923); Platygramme mucronata (Stirt.) A.W.Archer, Bibl. Lichenol. 94: 136 (2006).

Phaeographis australiensis Müll.Arg., Flora 65: 504 (1882).

Thallus pale grey, smooth, continuous, 30–120 µm thick, forming diffuse patches to 10 cm wide which often fuse together into extensive colonies; calcium oxalate abundant between the cortical and photobiont layers. Lirellae scattered or crowded, simple or sparsely branched, straight or sinuous, 0.8–4 mm long and 0.2–0.3 mm wide, with a thin, basal thalline margin; disc usually obscured, black. Exciple in section carbonised entirely, usually convergent at the base, sometimes only thinly, laterally 12–60 µm thick. Hypothecium 10–30 µm thick. Hymenium 65–120 µm thick, not inspersed, hyaline apart from a brown epithecial layer; asci 80–100 × 19–25 µm; paraphyses 1.5–2.5 µm wide. Ascospores transversely 7–12-septate, at first hyaline, later becoming pale brown, ultimately deep brown and deformed, (30–)34–43.5–57(–64) × 7–9.0–11(–11.5) µm, with a hyaline mucronate extension 2–5 µm long at both ends or at the distal end only.

Chemistry: norstictic and connorstictic acids, frequently in such low concentrations that TLC is required for detection because spot tests with K and P are unreliable, and the characteristic red, needle-like crystals that form when microscope sections are eluted with K are frequently not seen.

Very common and widespread in coastal areas (including the Bass Strait islands), and often the dominant epiphyte in Acacia longifolia subsp. sophorae-dominated scrub, where it forms extensive thalli associated with Lecanora flavopallida and Flavoparmelia rutidota. Less commonly, it is found in inland areas on garden trees, in dry sclerophyll forest, heathland, wet sclerophyll forest and, rarely, on canopy limbs in the rainforest canopy. It is also known from the southern Australian mainland and New Zealand. The enigmatic characters of this lichen are reflected in its chequered taxonomic history, which has seen it included in Graphis, Phaeographis and Platygramme. It also has numerous nomenclatural synonyms, although only those relevant to Tasmanian literature are cited above; for others see Lücking et al. (2011).

Granville Harbour, 41°49’S 145°02’E, 20 m, 2009, P. James & G. Kantvilas 249/84 (BM, HO); Fossil Cliffs, Maria Island, 42°35’S 148°05’E, 100 m, 2014, G. Kantvilas 434/14 (HO); Cape Portland, Musselroe Wind Farm, 40°48'35"S 148°06'23"E, 20 m, 2018, G. Kantvilas 245/18 (HO).

References