Flora of New Zealand Series

Holotype: New Zealand. Otago, Potters, Old Man Range, 1200m, 26 February 1998, D.J. Galloway 0239–CHR. Isotype – UPS.

Description : Description : Thallus crustose, irregularly spreading, 1.5–5(–10) cm diam., white, creamish white to greyish white, knobbly-verrucose-papillate; papillae densely congested to rather sparsely developed; prothallus not evident. Apothecia, common, densely crowded to widely scattered, round to irregular, often distorted through mutual pressure, sessile, constricted at base, (0.1–)0.5–1.5(–2.5) mm diam., disc black, matt, slightly sooty to subnitid, epruinose, subconcave at first, becoming plane to convex, occasionally with secondary apothecia or lobules developing on older, crowded discs; margins concolorous with disc, distinctly thickened and raised, persistent even in mature fruits. Exciple of radiating cells, brownish to olive-black in section, 50–75 μm thick at sides, continuous with hypothecium. Hypothecium dense, brown-black. Epithecium granular, reddish brown to brown-black, 12–16 μm thick. Hymenium hyaline to very pale straw-yellow, 80–90(–100) μm tall, paraphyses densely conglutinate, septate, 1.4–1.8 m diam., apices swollen, to 2.5 μm diam. Ascospores ellipsoidal, brown to grey-brown, 1-septate, thin-walled, slightly constricted at septum, apices pointed, contents often ±vacuolate, (13.5–)15–21.5(–25) × 5–6.5(–7.5) μm.

Chemistry : Thallus K+ dingy yellow, C+ orange, KC+ orange-red; containing atranorin (minor) and 6- O -methylarthothelin (major).

S: Central Otago Mountains (Dunstan Ra., Old Man Ra.). On exposed summit tundra and fellfield, and in tussock grassland where it grows over dead grass, decaying moss, plant detritus, and old rabbit droppings on soil in inter-tussock spaces (Galloway et al. 1998: 7). It associates in these habitats with Frutidella caesioatra, Lepraria neglecta, Megaspora verrucosa and Rinodina olivaceobrunnea.

Endemic

Illustrations : Nordin (2004: 356, fig. 1; 357, fig. 2).

Tetramelas confusus is characterised by: the terricolous habit; a wide-spreading, whitish, warty-papillate thallus; often numerous, jet-black, epruinose, lecideine apothecia with a well-developed slightly raised margin to the discs; grey-brown, 1-septate ascospores, 13.5–25 × 5–7.5 μm. Sterile thalli could be mistaken for Lepraria incana or sterile Brigantiaea fuscolutea, but the characteristic thallus chemistry discriminates Tetramelas confusus from these superficially similar and often sympatric taxa. The presence of 6- O -methylarthothelin in New Zealand specimens provisionally assigned to T. papillatus suggests that the New Zealand material might be closer to the arctic-alpine species T. insignis (Nägeli ex Hepp) Kalb, but further studies are needed to clarify this. Nordin (2004) reports that in its character traits, T. confusus is intermediate between the arctic-alpine species T. papillatus  s. str., and T. insignis. Tetramelas papillatus has a thicker, whiter and more coherent thallus; smaller, broadly sessile apothecia with margins that are not flexuous and often excluded, and it does not contain 6- O -methylarthothelin. In T. insignis the apothecia are distinctly larger than in either T. confusus or T. papillatus, and the thallus does not contain atranorin (Nordin 2004: 357, tab. 1).