Diagnosis:—Thallus erectus; basi leviter rubescens; ramuli irregulares; soralia punctiformia, interdum agregata vel conjuncta; cortex nitidus et valde crassus (proportione 16–18%); medulla valde tenuis (3–4.5%) et K– (substantiam incognitam et UV+ viridis continente).
Type:—ECUADOR. Galápagos Islands: Isla Sán Cristóbal, Cerro Mundo, at the top of the rock cliffs on the S side close to the summit, 00°53’S, 89°34’W, 282 m, transition zone with Bursera graveolens, Croton scouleriand Jasminocereus thouarsii, on Jasminocereus thouarsii on the ridge, August 2008, Clerc & Truong 08-405(holotype CDS, isotypes G, CMA: 16/3/61.5; chemistry: usnic acid, unknown medullary metabolite reacting UV+ green after charring).
Thallus fruticose, up to 8 cm long, erect and strongly shrubby, often with several attachment points. Base concolorous with thallus, usually with a reddish tinge. Branching distinctly anisotomic-dichotomous. Branches irregular to tapering, not constricted at their attachment point. Section of branches terete to slightly flattened or ridged. Terminal branches with few divisions and thickened at the tips. Fibrils few or absent. Papillae hemispherical, often numerous. Soralia minute, often aggregating in small packs or fusing and thus looking like a large single soralium, developing on top of papillae or directly on the cortex ad initio, remaining plane with a distinct cortical margin, rarely becoming slightly stipitate or efflorescent, but never excavating. Isidiomorphs present, very small. Apothecia not seen. Cortex thick (15.5–19.5% of branch width, n = 10), very hard and vitreous in longitudinal section of branch. Medulla compact, usually very thin and almost indistinct (3–4.5%), rarely thicker (up to 10%) close to the base. Axis very thick (54.5–62%). Medulla K–, C–, P–. Secondary metabolites detected by thin layer chromatography (n = 9): usnic acid and an unknown compound reacting UV+ green after charring (RF classes: solvent A = 6; B = 3; C = 5).
Distribution and habitat:—Endemic to the Galápagos Islands, so far known from Isabela, Sán Cristóbal and Santa Cruz Islands. This species usually grows on exposed habitats, for instance along ridges or on the slopes of the volcan’s crater. It was found in the transition vegetation zone, seldom in the arid and humid zones. Substrate: on rocks, on cactus and more rarely on bark (for exemple trunks of Bursera graveolens). Etymology:—The epithet refers to the location where this species was discovered.
Additional specimens examined (paratypes):— ECUADOR. Galápagos Islands: Isabela, Volcán Alcedo, Aptroot 64769A (CDS). Isabela, Volcán Darwin, SW slope, Bungartz 7862B (CDS). Sán Cristóbal,sector of the “gotera de agua”, Clerc & Truong 08-330 (CDS, G). Santa Cruz, N side of the island, Aptroot 64568 (CDS 31140).
Usnea is a large genus of c. 350 mainly corticolous species Swinscow & Krog 1979, Clerc 1987, 2006, 2008, Halonen et al. 1998, Herrera-Campos et al. 1998, Ohmura 2001, Stevens 2004). The genus is characterized by the fruticose thallus, branches holding a central axis and the presence of usnic acid in the cortex (Clerc 1998). This new species, so far endemic to the Galápagos, is characterized by anisotomic-dichotomous branching, terminal branches with few divisions, the absence of fibrils and the minute soralia developing from low papillae or on the cortex of branches, often aggregating in packs or fusing. Anatomy in longitudinal section of branch is very characteristic, with a thick, very hard and vitreous cortex, a thick axis and a very thin, almost indistinct medulla. TLC analysis revealed the presence of a new unknown substance in the medulla, reacting UV+ green after charring. The cortex of U. subscabrosa Motyka (Herrera-Campos et al.1998) is similar to U. galapagona, but the former species is pendulous, with a very different morphology, chemistry and ecology.
from: Lumbsch, H.T., Ahti, T., Altermann, S., Amo De Paz, G., Aptroot, A., Arup, U., Bárcenas Peña, A., Bawingan, P.A., Benatti, M.N., Betancourt, L., Björk, C.R., Boonpragob, K., Brand, M., Bungartz, F., Cáceres, M.E.S., Candan, M., Chaves, J.L., Clerc, P., Common, R., Coppins, B.J., Crespo, A., Dal Forno, M., Divakar, P.K., Duya, M.V., Elix, J.A., Elvebakk, A.V., Fankhauser, J., Farkas, E., Ferraro, I.L., Fischer, E., Galloway, D.J., Gaya, E., Giralt, M., Goward, T., Grube, M., Hafellner, J., Hernández M., J.E., De Los Ángeles Herrera Campos, M., Kalb, K., Kärnefelt, I., Kantvilas, G., Killmann, D., Kirika, P., Knudsen, K., Komposch, H., Kondratyuk, S., Lawrey, J.D., Mangold, A., Marcelli, M.P., Mccune, B., Messuti, M.I., Michlig, A., Miranda Gonzáles, R., Moncada, B., Naikatini, A., Nelsen, M.P., Øvstedal, D.O., Palice, Z., Papong, K., Parnmen, S., Pérez-Ortega, S., Printzen, C., Rico, V.J., Robayo, J., Rosabal, D., Ruprecht, U., Salazar Allen, N., Sancho, L., Santos De Jesus, L., Santos Vieira, T., Schultz, M., Seaward, M.D.R., Sérusiaux, E., Schmitt, I., Sipman, H.J.M., Sohrabi, M., Søchting, U., Søgaard, M.Z., Sparrius, L.B., Spielmann, A., Spribille, T., Sutjaritturakan, J., Thammathaworn, A., Thor, G., Thüs, H., Timdal, E., Truong, C., Türk, R., Umaña Tenorio, L., Upreti, D.K., Van Den Boom, P., Vivas Rebuelta, M., Wedin, M., Will-Wolf, S., Wirth, V., Wirtz, N., Yahr, R., Yeshitela, K., Ziemmeck, F. & Lücking, R. (2011): One hundred new species of lichenized fungi: a signature of undiscovered global diversity. Phytotaxa18: 1-127.
Usnea galapagonaTruong & P.Clerc in Lumbsch et al. Phytotaxa18: 110 (2011).
Type: Ecuador. Galápagos, Isla San Cristóbal, Cerro Mundo, at thetop of the rock cliffs on the S side close to the summit, 0°53.0'19.5''S, 89.0°34.0'24.3''W, 282 m alt., transition zone, with Bursera graveolens, Croton scouleri and Jasminocereusthouarsii, on Jasminocereus thouarsii on the ridge, 25-Aug-2008, Clerc 08-405 [holotype in CDS (40259); isotypes in G]. %C/M/A: 16/3/61.5. Chemistry: usnic acid, unknown medullary metabolite (reacting UV+ green after charring).
Short Description. A detailed description of U. galapagona can be found in Lumbsch et al. (2011); particularly characteristicfor the species is its unusual anatomy with a thick, hard and vitreous cortex, a thick axis, and a very thin, almost indistinct medulla. The species is further characterized by erect thalli with a reddish tinged base and anisotomic-dichotomous branches, typically only sparsely divided, lacking fibrils. Among sorediate Usnea species of the Galapagos, U. galapagona is the only species with such a thick cortex that is very rigid and thus difficult to section. Its minute soralia are not enlarging but can aggregate or fuse, although they do not completely cover the branch apices.
Chemistry. Medulla with an unknown substance, in TLC reacting UV+ green after charring [P–, K–, C–, KC–].
Ecology and distribution. Endemic to the Galapagos, first reported from Isabela (Volcán Alcedo), San Cristóbal and Santa Cruz (Lumbsch et al. 2011); since then, the species has also been found on Pinta and Floreana, and on Volcán Darwin (Isabela). It is moderately common, mostly grows in the transition zone, typically in open Bursera woodland or Croton scrub, in exposed habitat, on bark (including cacti), or rock. Only few specimens have been collected in the humid zone, either on exposed rock or on branches in Tournefortia scrub.