Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Thallus: areolate, sometimes rimose at the edge, (1-)2-7 cm in diam., (0.1-)0.2-0.4(-0.8) mm thick areoles: angular, sometimes round or irregular, flat or slightly concave, (0.2-)0.4-1(-1.6) mm in diam., contiguous, separated by cracks prothallus: sometimes present along the thallus edge, forming a dark zone or fimbriate, olive-black to blue-black or black, 0.1-0.4(-2) mm wide surface: brown to gray-brown or olive-brown, sometimes gray, usually with contrasting white rims around the apothecia; dull to slightly shiny upper cortex: 20-35(-40) µm thick, uppermost part ±brown, 5-15(-20) µm thick, with cells 5-7(-10) µm in diam.; cortex covered with an epinecral layer 3-12(-20) µm thick photobiont: chlorococcoid, cells ±round, 5-16(-22) µm in diam. Apothecia: aspicilioid, rather common, 0.1-0.4(-0.6) mm in diam., 1-2(-4) per areole, round to angular, sometimes elongated disc: black, concave, rarely plane, without pruina or sometimes with a thin, white pruina thalline margin: flat to slightly elevated, rarely prominent, usually with a white to gray rim exciple: 20-50(-60) µm wide, I-, sometimes partly I+ blue medially; uppermost cells brown, ±globose, 5-6(-7) µm in diam. epihymenium: green to olive or olive-brown, sometimes blue-green, rarely brown, without or with a few crystals, rarely with numerous crystals, N+ green to blue-green, K+ brown to green-brown hymenium: hyaline, I+ persistently blue, (100-)130-170(-200) µm tall paraphyses: submoniliform, sometimes slightly moniliform, with (0-)1-3(-5) upper cells ±globose, 3-5(-6) µm wide, in lower part (1-)1.5-2 µm wide, slightly branched and anastomosing subhymenium and hypothecium: pale, I+ persistently blue, sometimes partly I-, together (20-)40-70(-90) µm thick asci: clavate, 70-105(-120) x (18-)20-32(-35) µm, 8-spored ascospores: hyaline, simple, ellipsoid, (16-)19-26 x (9-)10-15(-19) µm Pycnidia: rare to rather common, 1(-3) per areole, immersed, (100-)110-200 µm in diam., with a black, punctiform to sometimes elongated ostiole, often surrounded by a white rim, 60-90(-110) µm in diam. conidia: filiform, straight or slightly curved, (10-)14-23(-28) x 0.8-1 µm Spot tests: cortex and medulla I-, K-, P-, C- Secondary metabolites: none detected by TLC, or rarely an unknown substance (Rf 0-1 and brown-black in TLC C-system; found in 1 specimen). Substrate and ecology: on ±exposed siliceous rock World distribution: western North America (type from Oregon) Sonoran distribution: California, at 550-2000 m. Notes: The type specimen of Aspicilia tenuis (U.S.A: Oregon, Crater Lake, 2100 m, August 1932, F.P. Sipe 950; UPS) is a tiny, rimose specimen with an olive-brown to gray thallus without hypothallus. It has small apothecia with a white to gray rim and submoniliform paraphyses. The spores, 8 per ascus, measure 17-25 x 13-16 µm and the conidia are (12-)15-22 µm long. The Californian specimens agree with the type specimen in many characters: the apothecia are small and have a white to gray rim, the paraphyses are submoniliform (to slightly moniliform), the spores are large and the conidia are long. In contrast to the type specimen, they have an areolate, not rimose, brown thallus. Aspicilia phaea differs from Aspicilia aff. tenuis by its shorter conidia; Aspicilia confusa by its gray thallus and dispersed, convex areoles; and Aspicilia cyanescens by its gray to blue-gray thallus, its prominent prothallus and its blue-green epihymenium. More material is needed to resolve the relationships within the Aspicilia aff. tenuis group. Molecular data would probably contribute to a better understanding of the taxonomy, but so far only an ITS sequence from a single specimen (Riverside County; Owe-Larsson 9167:a) is available. Some specimens from San Benito, Santa Barbara and San Luis Obispo Counties agree with this group in all characters but the moniliform paraphyses and the convex areoles, and are also in need of further study.