LITHOGRAPHA ^{1 2}

Gintaras Kantvilas ³

Lithographa Nyl., Acta Soc. Linn. Bordeaux 21: 393 (1857).

Type: L. petraea (Nyl.) Nyl. [= L. tesserata (DC.) Nyl.]

Thallus crustose, ecorticate, with or without a prothallus. Photobiont a green alga, possibly Chlorella, with ± globose cells 6–15 µm wide, encased in a gelatinous sheath. Ascomata apothecia, lirelliform. Proper exciple cupulate, opaque and carbonised throughout, composed of heavily conglutinated, compacted, brownish, indistinct hyphae. Paraphyses branched and anastomosed, with the apices not capitate. Asci clavate, 8-spored, approximating the Trapelia-type: outer wall intensely amyloid, developing a thin, amyloid, apical cap; tholus well-developed, very weakly amyloid to non-amyloid, usually with somewhat more intensely amyloid flanks; ascoplasm truncate to concave at the apex; ocular chamber absent. Ascospores mostly simple, rarely transversely septate to submuriform, hyaline, sometimes becoming brown with age, thin-walled, occasionally thinly halonate. Conidiomata pycnidia, immersed. Conidia bacilliform. Chemistry: norstictic or gyrophoric acids occur in some species; otherwise lacking substances.

A genus of about 15 species, found on rocks in cool to cold environments in both hemispheres. Although superficially similar to Opegrapha, that genus differs by having a trentepohliod photobiont, different asci and transversely multi-septate ascospores. Lithographa was previously included within a broad concept of Trapeliaceae, but molecular data (Resl et al. 2015) now place it in the related family Xylographaceae, together with Lambiella and Xylographa. It is most similar to the former, which differs chiefly by having essentially rounded, ± disciform apothecia. The lirelliform apothecia of the single Tasmanian taxon make it easily recognisable.

Key references: Hertel & Rambold (1990); Lumbsch (1997); Coppins & Fryday (2006); Resl et al. (2015); Cannon et al. (2021).

1 Lithographa graphidioides (Cromb.) Imshaug ex Coppins & Fryday

Lichenologist 38: 94 (2006); —Stigmatidium graphidioides Cromb., J. Linn. Soc., Bot. 15: 233 (1876).

Lithographa subantarctica Hertel & Rambold, Biblioth. Lichenol. 38: 158 (1990).

Thallus very thin, wispy, rimose, dull brown to black-brown, forming discontinuous patches that follow the topography of the substratum, sometimes highly reduced and carbonised and occurring only at the base of the ascomata; prothallus absent. Lirellae 0.4–1 mm long, 0.15–0.6 mm wide, straight or a little curved, simple or sparingly branched into a 3–4-pointed star, scattered or aggregated in rather gnarled groups to c. 1.5 mm wide; disc slit-like; exciple jet-black, glossy, ± completely obscuring the disc, in section 50–120 µm thick laterally, 70–150 µm thick basally. Hypothecium hyaline to pale brown, 20–30 µm thick. Hymenium 80–110 µm thick, hyaline, brownish inthe uppermost part, remaining coherent in K; paraphyses 1–1.5 µm thick; asci 65–80 × 14–20 µm. Ascospores simple, broadly ellipsoid, 11–14.4–17(–18) × 6–8.8–11(–12) µm. Conidia not found in Tasmanian specimens, reported (Coppins & Fryday 2006) as 6–11(–13) × 0.8 µm.

Chemistry: no lichen compounds detected by TLC; all spot tests negative.

An inconspicuous species, widely distributed in southern subpolar regions, but known in Australasia only from Tasmania, where it has been rarely collected but is likely to have been overlooked. It is found in moist, open, sunny habitats in heathland and buttongrass moorland, typically on small, scattered pebbles of hard, highly siliceous rocks such as Precambrian quartzite. Previously-disturbed sites such as abandoned gravel quarries, helipads and roadsides provide ideal habitats.

Mt McCall, 42°22’S 145°43’E, 720 m, 1984, G. Kantvilas 225/84 & P. James (BM, HO); helipad at Strathgordon, 42°46’S 146°03’E, 360 m, 1985, G. Kantvilas 169/85 (BM, HO, M); Gordon River Road, N of Frodshams Pass, 42°46’S 146°24’E, 500 m, 2019, G. Kantvilas 70/19 & J. Jarman (HO).

References