Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.
Thallus: usually to (1-) 3-5 (-20) cm tall, pliant, 3-8 cm wide, erect or spreading, caespitose to subpendent and beard-like, ± copiously branched and entangled; branching: irregular, often forked and divaricate especially towards the tips branches: ± crowded, 0.5-1.5 (-3) mm wide, angular, rarely cylindrical, repeatedly bent, loose; long branches: with densely crowded, thin, subulate; side branches: somewhat curved terminally, often with acuminate tips surface: lemon yellow, golden yellow-green to chartreuse, often distinctly greenish yellow, rarely sulfur yellow, in age or towards the base, usually pale orange- yellow to light yellowish brown; older branches: sometimes greenish gray to gray with the younger branches brighter yellow; extreme tips: often dark grayish brown; lacunate or foveolate soredia: diffuse, often isidioid, generally dense, often developing from paler, brighter yellow areas or cracks on the angles and ridges, where the cortex has degenerated; isidia absent to few when soralia abundant, < 0.05 mm diam., globular and ± constricted at the base, or irregularly elongated to c. 0.1-0.2 mm and narrowing towards the tips, or sometimes becoming dense especially near the base, then ± cylindrical, becoming more elongated and branched (± coralloid) Apothecia: very rare (usually absent in material from Sonoran region), up to 20 mm wide; disc brown Pycnidia: rare (usually absent) Spot tests: cortex and medulla K-, C-, KC-, P- Secondary products: cortex with vulpinic acid. Substrate and ecology: on bark or wood, usually the trunks or branches of living or dead conifers or man-made wooden structures, rarely on acidic rock; to the north very common and often covering large areas of tree surfaces above the snow line World distribution: western North America and western Eurasia Sonoran distribution: southern California and Baja California at 800-2000 m, often on north-facing slopes or in shaded areas, but also sometimes in chaparral; rare, eastern Arizona at 2950 m. Notes: Based on morphology and distribution, material of L. vulpina s. lato from the Sonoran region appears to include both L. vulpina s. str. (especially near the coast, and similar to European material) and the L. lupina (especially away from the coast, and yellower, more highly branched, and with larger and more diffuse soralia) morph of Kroken and Taylor (2001). However, in my opinion the differences between these two morphs, as given by these authors and by Goward (1999), are not very consistent and are difficult to apply to the often poorly developed specimens found in southern California, where the distributions of the two morphs overlap. A few specimens from the San Gabriel Wilderness are much more robust and have sparsely divided main branches 2-3 (-7) mm wide with narrow branches mostly in the upper parts; in these morphs the narrow branches are either divaricately branched in scattered dense clusters, or more parallel and sinuous and concentrated towards the tips with extensive coverage by isidioid soredia concentrated on these smaller branches. These and other populations from arid areas may represent additional species (Barreno, pers. comm.).