Flora of New Zealand Series

≡Lecidea demersa Kremp., Verhandl. zool.-bot. Ges Wien 26: 455 (1876).

≡Diomedella demersa (Kremp.) Hertel, Beih. Nova Hedwigia 79: 445 (1984).

=Lecidea melastroma Nyl., Lich. Nov. Zel.: 107 (1888).

Holotype: New Zealand. Sine loco [probably Wellington], Charles Knight – M. Isotype– M.

Lecidea melastroma. Holotype: New Zealand. Westland, Greymouth, 1887, Richard Helms 241 – H-NYL 16081.

Descriptions : Flora (1985: 230). See also Rambold (1989: 91).

Chemistry : Cortex K+ yellow, C−, P ±yellow; medulla K−, C−, P–; containing atranorin and an unidentified fatty acid.

N: Wellington (Tararua Ra.). S: Nelson (Cobb Valley Mt Benson, Denniston Plateau), Westland (Kelly Ra.), Canterbury (Craigieburn Ra., Mt Wakefield, Hakataramea Valley), Otago (Lake Ohau, Silver Peak). St: (Mt Allen, Tin Ra., Fraser Peaks). A subalpine to high-alpine species, spectacularly developed on the sandstone pavements of the Denniston Plateau north of Westport, and also commonly developed on piles of stones and boulders removed from the surface of paddocks in inland Canterbury, where it forms conspicuous black and white patches among yellow patches of Rhizocarpon geographicum and rust-red patches of Tremolecia atrata. Known also from alpine rocks in Australia (Rambold 1989: 93; McCarthy 2003c, 2006; Lumbsch & Elix 2004).

Australasian

Illustrations : Rambold (1989: 92, fig. 7); Malcolm & Galloway (1997: 20, 69, 100, 157); Malcolm & Malcolm (2000: 131).

Lecanora demersa is characterised by: the saxicolous habit (alpine to high-alpine rocks); its innate to immersed, black apothecia contrasting with the white to grey-white areolate thallus; the often well-developed thick black prothallus that is visible at the thallus margins and between the areolae; filiform, curved conidia, 25–35 × 0.8–1 μm. L. demersa is related to a subantarctic species, L. disjungenda (Cromb.) Hertel & Rambold, m Kerguelen and Marion I. (Dodge 1948: 167; Hertel 1984b; Rambold 1989: 90–92), the two taxa formerly being united in the genus Diomedella, having Lecanora -type asci and immersed, aspicilioid apothecia, with a colourless hypothecium and a reduced exciple (Hertel 1984b: 445). It is distinguished from L. oreinoides (q.v.) by the larger apothecia (0.5–1.2 mm diam.) and the thicker, broader black prothallus and the filiform conidia.