Chapsa thallotrema N. Salazar & Lücking
Mycobank MB 517753
Thallus grey-olive, smooth to uneven, with dense, prosoplectenchymatous cortex with internal splitting, sorediate; soralia usually numerous but discrete, capitate, finely granular, 1–2 mm diam., white to bluish or yellowish white, strongly contrasting with the surrounding thallus; photobiont layer and/or medulla with clusters of calcium oxalate crystals. Apothecia erumpent, angular-rounded, 1–3(–5) mm diam.; disc exposed, flesh-colored to pink-purple; margin lobulate to recurved, often layered, flesh-colored to beige. Columella absent. Excipulum paraplectenchymatous, colourless; periphysoids present. Hymenium 150–200 µm high; paraphyses unbranched. Ascospores 2–4/ascus, 15–19-septate, 60–120 x 10–15 µm, cylindrical, with thick septa and lens-shaped lumina, colourless, I+ violet-blue (amyloid). Secondary chemistry: stictic acid and satellites (K+ yellow).
This new species is part of a complex of species centered around Chapsa sublilacina (Ellis & Everh.) Sipman & Lücking, all sharing the thallus morphology and ascospore type. Four forms are distinguished: with or without stictic acid and satellite substances, and with either large, compact, finely granular soralia or with small, irregular, coarse soralia. The form with large soralia, described here as C. thallotrema, contains stictic acid, whereas the form with small soralia lacks secondary substances. Thus, C. thallotrema is considered the sorediate counterpart of C. sublilacina.
This common and widespread taxon was long ago recognized by Henry Imshaug and his students from collections in the Caribbean and provisionally named Thallotrema antillarum but never validly published. The chosen epithet honours this earlier discovery.
Apparently a widely distributed neotropical species restricted to the shady understory of lowland to lower montane rainforests.
Type:—PANAMA. Panamá: Altos de Campana National Park, 50 km W of Panama City near the town of Capira; 8º42’N, 79º57’W, 500–600 m; submontane rainforest, on bark of large trees in the shaded understory; Lücking 27305 (holotype F; isotype PMA).
Additional specimens examined (paratypes):—COSTA RICA. Alajuela: Volcán Tenorio National Park, Pilón Biological Station (Arenal-Tempisque Conservation Area), Tilarán Ridge, 140 km NW of Sán José, 25 km NNW of Tilarán, near Bijagua, Nelsen 3745 (INB, WIS), Lücking 17219 (F); ibid., main trail through forest to crater; Will-Wolf 12745b (CR, INB, WIS). Puntarenas: Corcovado National Park, Sirena Section, Sirena Biological Station (Osa Conservation Area), Osa Pensinsula, 160 km SSE of Sán José and 50 km WSW of Golfito, Lücking 16204 (F, USJ); 16228 (F, INB). PANAMA. Panamá: Altos de Campana National Park, 50 km W of Panama City near the town of Capira, Lücking 27303, 27304 (F; PMA).
Sicut Chapsa sublilacina sed thallo sorediis instructo differt.