Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Life habit: lichenized, not lichenicolous Thallus: crustose, mostly over 4 cm across, appressed, 0.3-0.4 mm thick, composed of granular-verrucose areoles, forming minute, radiating lobes at the thallus margin; prothallus: dark, sooty black, with very dark greenish blue hyphae 4-5 µm thick and thick-walled areoles: convex, weakly peltate surface: chestnut brown to coppery red or brown, usually shiny, sometimes sorediate soredia: white to brown, in 0.2-0.3 mm wide soralia thallospores: on prothallus and in places along the lower sides of margins of areoles, sooty-black, 2-celled to submuriform (4-6+ celled), coarsely warted, green-black, 9-14(-20) x 6-12 µm, the cytoplasm distinctly stained in lactophenol-cotton blue, K+ somewhat paler, N+ purple cortex: phenocortical with dead algal cells, pale brown or brown (colorless in K), with dark brown crystals (not transparent) soluble in K, 10-17 µm thick, with cells 1.2-2.5 µm in diam., often with an epinecral layer 7-15 µm thick medulla: +gray, opaque, composed of loosely interwoven hyphae 3-4 µm thick and I+ dark blue, strongly swelling, without hyphal bundles; hyphae: very intricate, moderately thick-walled, the lumina rounded or stretched or +subcylindrical; algal layer: 50-85 µm thick with even upper surface; algal cells: scattered, 1015 µm in diam. Apothecia: rare, often poorly developed or absent, sessile, pseudolecanorine (to lecanorine), (0.3)0.5-0.8 mm in diam. disc: red- to brown-black or black margin: entire, concolorous with areoles amphithecium: with a phenocortical cortex with a few dead algal cells, c. 30 µm wide, continuous with and similar in structure to the thalline one, smooth outside, with gelatinous layer, outer 4-5 µm darker brown; end cells: partly with brown pigment caps, poorly delimited from amphithecium by greater swelling of the hyphae, diffusely dark brown, with rather few fine granules soluble in K; algal layer: thick, in margin and below hypothecium exciple: absent laterally epihymenium: diffuse +olive to dark yellow-brown, 6-9 µm thick hymenium: almost hyaline, (40-)50-90 µm tall; paraphyses: firmly coherent in water, distinct in K, c. 1.7 µm thick, with upper cells irregularly convex and apices discrete, 2.5-3.5 µm wide, pale brown; hypothecium: hyaline or pale yellow, chondroid, 60-120 µm thick asci: short-clavate to vesicular (+inflated), 25-35 x 10-12 µm, 8-spored ascospores: hyaline, simple, ellipsoid to oblong-ellipsoid, 7-10(-12) x 3-3.5(-4.5) µm Pycnidia: perhaps not rare but confused with abortive apothecia, ostiole black, prominent, immersed in low verrucae, with a cavity c. 200 µm broad, 150 µm deep; wall: thin, pale conidia: hyaline, straight or curved to +arcuate, 12-14(-20) x 0.8-1 µm Spot tests: cortex K-; medulla K+ yellow to yellow-brown or orange, C-, KC- or KC+ reddish violet, P+ yellow or orange, UV- Secondary metabolites: medulla with stictic and constictic acids or lobaric acid. Substrate and ecology: on overhanging surfaces of heavy metal-containing siliceous rocks (granite, schist, quartzite) World distribution: Europe and North America Sonoran distribution: not currently known but expected as it is reported from central California (Herre 1944) at 830-1800 m. Notes: For comparison of P. nephaea with P. atriseda, see notes under that species. When sterile, P. nephaea often resembles a gray-brown Rhizocarpon species. Beside P. nephaea, P. leproloma (R. Sant.) Rambold & Poelt is another species that irregularly produces thalloconidia. The latter species is a parasite on Lecidea paupercula and is so far known only from Europe (Poelt and Obermayer 1990).