Lecanactis minutissima Weerakoon & Aptroot, 2016

Weerakoon, Gothamie & Aptroot, André, 2016, Nine new lichen species and 64 new records from Sri Lanka, Phytotaxa 280 (2), pp. 152-162 : 155

Lecanactis minutissima Weerakoon & Aptroot , sp. nov. ( Fig. 1F–G )

Mycobank No.: MB 817610

Lecanactis with pale ochraceous thallus, apothecia sessile , disc dark brown, c. 0.2–0.5 mm wide, with thick white granular pruina through which the disc can be seen, proper margin flush with disc, densely pruinose, ascospores hyaline, consistently 3-septate, curved, somewhat clavate, 13–18 × 2–3 μm.

Type: — SRI LANKA. Morningside, on bark of dead Syzygium tree, 25 April 2015, G.Weerakoon Mo21A (holotype PD, isotypes ABL & F).

Thallus crustose, continuous, not corticate, dull, pale ochraceous, epiperidermal, not surrounded by a prothallus. Algae trentepohlioid. Apothecia sessile, round or to somewhat angular or ellipsoidal, disc dark brown, c. 0.2–0.5 mm wide, with thick white granular pruina through which the disc can be seen; proper margin flush, concolourous and equally pruinose, c. 0.1 mm wide. Epihymenium with thick layer of relatively large crystals. Hypothecium and excipulum black, except for a hyaline thick layer of relatively large crystals at the outside of the excipulum. Hamathecium not inspersed, weakly amyloid, paraphysoids 1–1.5 μm wide, anastomosing and often somewhat curled. Asci cylindrical, 30–37 × 9–11.5 μm, Abietina-type sensu Egea & Torrente (1994). Ascospores 8/ascus, hyaline, consistently 3-septate, curved, somewhat clavate, 13–18 × 2–3 μm, ends rounded, without gelatinous sheath. Pycnidia not observed. Chemistry. Thallus UV–, C–, K–, KC–, Pd–. TLC: No substances detected.

Distribution and habitat: —On stringy bark of dead tree in wet tropical mountain forest. Only known from Sri Lanka.

Discussion: —This species is most similar to the neotropical Lecanactis dubia Merrill in Millspaugh & Nuttall (1923: 364), which differs by the longer and especially wider ascospores of 16–23 × 3–4 μm and the absence of pruina. Also somewhat similar ito Lecanographa illecebrosula (Müll.Arg.) Egea & Torrente (1994: 141) , which differs by the Pd+ yellow reaction, the gelatinous sheath around the ascospores and the non-pruinose apothecium margins.

Figures

FIGURE 1. A–B, Astrothelium conjugatum, A, habitus, B, ascospores; C–E, Heterodermia fragmentata, C, apothecium, D–E, thallus; F–G, Lecanactis minutissima, F, apothecia, G, ascospores; H–I, Megalotremis cylindrica, H, conidiomata, I, conidia and conidiophores. Scale:A, H = 0.5 mm, B = 25 μm, C = 2 mm, D–E = 1 mm; F = 0.2 mm, G = 20 μm, I = 10 μm.