Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: crustose, continuous or rimose-areolate; prothallus: not visible areoles: flat, thin or thick, opaque, ecorticate surface: smooth or rough, yellowish white to yellowish gray or yellowish brown or white to cream-colored, epruinose, with an indistinct margin, esorediate Apothecia: subimmersed or subimmersed when young, sessile when mature, 0.4-1.2 mm in diam., lecanorine disc: red-brown or orange-brown, plane, epruinose or slightly pruinose whitish gray margin: concolorous with thallus, thin or thick, persistent, even, not flexuose, smooth, entire, without a parathecial ring amphithecium: present, with numerous algal cells, with large crystals insoluble in K, corticate; cortex: distinct, basally thickened, gelatinous or interspersed, hyaline, 10-15 µm thick laterally, 20-25 µm thick basally parathecium: hyaline, containing crystals soluble in K epihymenium: red-brown to orange-brown, with pigment dissolving in K, with small crystals dissolving in K hymenium: hyaline, clear; paraphyses: not pigmented or red-brown to orange-brown, slightly thickened (up to 3 µm wide) apically; subhymenium: hyaline, 15-20 µm thick; hypothecium: hyaline, without oil droplets asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid or narrowly ellipsoid, (10-)11-13.5(-14) x (5.5-)6.5-7.5(-8) µm wide; wall: less than 1 µm thick Pycnidia: immersed, cerebriform; conidiophores: type II sensu Vobis conidia: filiform, (14-)16.5-19(-20) µm long Spot test: thallus and apothecial margin K+ yellow, C-, KC-, P+ yellow Secondary metabolites: containing atranorin (major), chloroatranorin (minor), chlorolecideoidin (minor), gangaleoidin (major), leoidin (minor) and norgangaleoidin (trace). Substrate and ecology: on exposed siliceous rocks World distribution: a pantropical species, common in the dry tropics and on coastal rocks Sonoran distribution: Baja California Sur, Sonora and Sinaloa. Notes: Lecanora sulfurescens is a distinct species wih its red-brown to orange-brown apothecial disc and the presence of gangaleoidin. L. gangaloides also contains the gangaleoidin chemosyndrome, but is readily distinguished, since it has black apothecial discs. Morphlogically similar are some morphotypes of L. plumosa that can be separated by a different chemistry and an epihymenium with coarse crystals, while L. sulfurescens has fine crystals.
Type: Brasil. Rio de Janeiro: exact locality unknown, 1869, Glaziou, A.F.M. 3850 [UPS–lectotype selected by Lumbsch & Elix (1993), PC–isolectotype].
Description. Thallus saxicolous, thin to moderately thickened, distinctly areolate, areoles initially scattered on a whitish fibrous to arachnoid prothallus, with age becoming contiguous, their edges closely adjoining; surface white to pale gray or pale greenish gray, roughened to verruculose, dull, epruinose to whitish pruinose, lacking soredia; prothallus well developed, whitish arachnoid, but reduced with age and ultimately appearing as a whitish line delimiting the thallus, rarely blackened. Apothecia numerous, often very densely aggregated, circular to slightly irregular in outline, 0.4–1.1 mm in diam., immersed to adnate, rarely sessile, typically very crowded, cryptolecanorine to distinctly lecanorine with a roughened to barely verrucose, epruinose to whitish pruinose margin, concolorous with the thallus; disc plane to slightly convex, yellowish orange to brownish orange, epruinose or weakly pruinose; hymenium hyaline, not inspersed, epihymenium with crystals, almost hyaline to pallid yellowish brown (elachista-brown: dissolving in K, HCl± dull greenish, N−), both pigment and crystals soluble in K (chlarotera-type); proper exciple thin, indistinct, with few crystals insoluble in K; thalline exciple thick, ±corticate, with large crystals insoluble in K (pulicaris-type); hypothecium hyaline; ascospores 8/ascus, simple, ellipsoid to broadly ellipsoid, (6.9)–8.2–10.3–(11.9) × (4.5–)4.6–5.3(–5.9) μm (n = 30). Pycnidia not seen.
Chemistry. Thallus cortex including apothecial margin P+ yellow, C−, KC−, K+ yellow; with atranorin [major], ±leoidin [major], ±gangaleoidin [minor or major], ±chlorolecideoidin [minor]; [specimens analyzed with TLC: Bungartz, F. 4564 (CDS 28650), 3404 (CDS 27110)].
Ecology and distribution. Pantropical (North and South America, Africa, Australasia), previously reported from Galapagos (Weber 1986, Elix & McCarthy 1989, Guderley 1999); among the most common and most abundant saxicolous species, occurring throughout all vegetation zones, in a large variety of sheltered and exposed habitats, inside crevices and cracks, shaded overhangs, exposed cliffs, on the top of boulders, in dust rich habitats near the ground, and frequently also on tortoise carapaces.
Notes. As previously reported by Lumbsch & Elix (1993) L. sulfurescens is characterized by the gangaleoidin chemosyndrome. However, Guderley (1999) also included gangaleoidin deficient forms, and unlike Lumbsch & Elix (1993), treats L. depressa Fée as a synonym of L. sulfurescens. We follow this view: some Galapagos specimens here identified as L. sulfurescens contained only atranorin. Specimens from continental South America generally appear to have epruinose apothecial discs (Guderley 1999), while some specimens from the Galapagos have pruinose apothecia.