Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.

Thallus: usually effigurate, areolate to rimose-areolate centrally, determinate, orbicular and 1-5 cm wide or often irregularly shaped areoles: mostly angular, plane to convex, 0.4-1 mm in diam., 0.4-1 mm thick (usually appearing very thin), confluent and losing orbicular shape; marginal lobes: elongate, contiguous, apices expanded and blunt upper surface: yellow, glossy similar to Pleopsidium, plane to convex, rough, uneven, with fissures eventually becomingdivision lines on areoles, epruinose cortex: paraplectenchymatous, pale yellow throughout with obscure cells, 30-50 µm thick algal layer: even, dense medulla: white, intricately prosoplectenchymatous attachment: broad, without forming a stipe Apothecia: numerous in central areoles; occasional in outer areoles disc: yellow, sometimes with a black-tinge, immersed, punctiform, rarely up to 0.6 mm wide, usually much smaller epihymenium: dark or light yellow, conglutinated, 15-25 µm thick hymenium: hyaline to pale yellow above, 100-170 µm tall; paraphyses: 1.5-2 µm wide at base, apices barely expanded subhymenium: hyaline, 20-50 µm thick; hypothecium: 10-15 µm thick asci: clavate, 60-100 x 20-25 µm, 100+-spored ascospores: hyaline, simple, ellipsoid to narrowly ellipsoid, 4-6 x 1.7-2.2 µm, but sometimes varying in size Pycnidia: not observed Spot tests: UV+ orange, C+ red, KC+ red in cortex, medulla, and apothecia Secondary metabolites: rhizocarpic acid (minor), epanorin, gyrophoric acid (major), lecanoric acid (minor) (HPLC: J. A. Elix, pers comm.) World distribution: Mexico, southwestern United States Sonoran distribution: Arizona, Baja California Sur, Chihuahua, Sinaloa, and Sonora. Notes: Acarospora erythrophora is usually effigurate and has been mistaken for a Pleopsidium. The C+ red/KC+ red reactions are distinctive. Acarospora robiniae also occurs in Baja California but has only a C+ red cortex, a thallus generally composed of dispersed areoles with yellow discs, and a strictly maritime distribution. The type locality of A. erythrophora is in New Mexico, and it occurs inland in Arizona and Sonora.

Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.

parathecium: up to 60 µm thick, often forming parathecial crown Ecology and substrate: on sandstone and granite lateral cortices: paraplectenchymatous, 20-45 µm thick; cells: irregular, 3-4 µm wide; eucortex with a diffuse yellow layer above 10-25 µm thick, hyaline layer below 10-23 µm thick lower surface: lacking or ecorticate exciple: usually distinct, thick beneath subhymenium, broadening sometimes to 50-80 µm above disc, forming a inner ring around the disc Thallus: areolate, small, determinate, orbicular or not, less than 2 cm. across areoles: becoming squamulose, 2-4 mm. across, sometimes lobulate; margin: indistinct to distinctly effigurate; lobes: poorly developed, 0.5-1(-2) mm long, up to 1 mm thick upper surface: yellow-orange, smooth, becoming convex, epruinose cortex: 30-60 µm thick, with an outer, 20-40 µm thick yellowish brown layer and an inner, colorless layer algal layer: 50-200 µm thick; algae up to 10 µm diam. medulla: white, prosoplectenchymatous, intricate Apothecia: 1-3 mm wide, numerous on thallus disc: pale yellow, only slightly brown, scarcely darker than thallus with thalline margin, plane becoming convex to almost globose, sometimes corrugated, biatorine, margin completely excluded true exciple: colorless, 50-80 µm thick epihymenium: brownish yellow, 15-20 µm thick hymenium: hyaline, usually 50-70 µm tall; paraphyses: simple or poorly branched, 2 µm or less broad at base, not or scarcely thickened at apex asci: clavate, 70-80 x 15-20 µm, 100-200-spored ascospores: hyaline, simple, ellipsoid, 3.5-4.5 x 1.5-2 µm Pycnidia: immersed conidia: ellipsoid, 3-3.8 x 1.5-1.8 µm Spot tests: thallus UV+ orange, K-, C-, KC-, P- Secondary metabolites: containing rhizocarpic, acaranoic, acarenoic acids (race 1), or in N. America also rhizocarpic and roccellic acids (race 2). Substrate and ecology: on rock, especially under overhangs on cliffs World distribution: Antarctica, Europe, North and South America Sonoran distribution: southern California (Santa Cruz Island) . Notes: Pleopsidium chlorophanum differs from P. flavum in having a smooth, smaller squamulose thallus and larger apothecia. For a long time, all effigurate specimens from North America have been called Acarospora chlorophana going back to Tuckerman in the 1800's. Pleopsidium chlorophanum is a rare, alpine species in Europe. In contrast, Pleopsidium flavum is a Mediterranean species, which was recognized after P. chlorophanum, and it has a broader ecological amplitude. It is assumed P. chlorophanum occurs in North America at high elevations, but so far we have seen only one specimen from North American, a collection by Charis Bratt (#3436, SBBG!) from a rock in grassy filed on Santa Cruz Island in southern California.