Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.

Thallus: morphologically and anatomically indistinguishable from that of L. albicans (see preceeding description) Spot tests: thallus K+ yellow, C-, KC-, P+ persistent, rather pale yellow (rarely P-), UV- Secondary metabolites: atranorin, unidentified fatty acids, rangiformic acid (accessory). Substrate and ecology: on soil, or detritus with mosses, over volcanic or other acidic rocks, or in rock crevices, mainly Arctic-alpine World distribution: western North America, South America and South Africa Sonoran distribution: eastern and central parts of Arizona, 1830-3100 m. Notes: Lamb and Ward (1974) suggested that this taxon might be considered as a chemically deficient phase of L. albicans; they gave no rationale for their maintenance of it as a separate species in spite of lumping the other chemotypes as “chemical strains”, but the distribution pattern of L. gracilescens is somewhat different (common in South Africa and warm temperate areas; absent from the Arctic). The occurrence of rangiformic acid is apparently rare in Sonoran specimens. One specimen from Arizona (Pima Co., 1710 m), tentatively included under this species, contains (in addition to atranorin and unidentified fatty acids), an unidentified substance (Rf 5 in solvent C, purplish and UV- after charring).