Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: crustose, rimose-areolate, forming an irregularly rounded patch usually 2-5 cm across and up to 0.4 mm thick; prothallus: thin, black, sometimes visible between the areoles or along the thallus margin especially at the juncture of a different thallus, areoles: usually contiguous, becoming almost bullate, plane to convex, ecorticate surface: white to grayish white, cream-colored or pale yellow, smooth, shiny to dull, esorediate Apothecia: immersed in center of the areoles, 1-3 per areole, up to 0.5 mm in diam. disc: black, flat to slightly convex, sometimes with a dusting of white pruina margin: usually flat and continuous with the areole surface, up to 0.7 mm wide, without a parethecial ring parathecium: yellowish ochre, 10-20 µm wide epihymenium: dark olive green to bluish green, 10-15 µm thick hymenium: hyaline, 35-55 µm tall; paraphyses: unbranched, rarely anastomosing, below 1.5-2 µm wide, terminally globose up to 3.5 µm wide; subhymenium: hyaline; hypothecium: hyaline asci: clavate, I+ blue, c. 8-spored ascospores: hyaline, simple, ellipsoid, (7-)9-14 x 4-6.5(-7.5) µm Pycnidia: immersed conidia: hyaline, filiform, 10-16 x c. 0.8 µm Spot tests: cortex K+ yellow, C-, KC-, P+ yellow; medulla K-, C-, KC-, P- Secondary metabolites: upper cortex with atranorin and chloroatranorin, medulla with confluentic (major) and 4O-methylmicrophyllinic (minor) acids. Substrate and ecology: on a range of different acidic rocks in open to partially shaded habitats at intermediate elevations World distribution: temperate regions of North and South America, Africa, eastern Asia, Australasia and Oceania and extending towards the tropics in mountainous regions Sonoran distribution: common throughout the region at intermediate elevations in Arizona, Chihuahua, Sonora, Sinaloa and Baja California Sur. Notes: Superficially L. oreinoides is similar to some species of Buellia, which can be readily separated by their brown, 1-septate spores. At first glance L. oreinoides is also similar to L. subimmersa (below), but the latter species has an even flatter thallus surface, brown disc, somewhat smaller spores and a different medullary chemistry. Lecanora oreinoides differs from similar lecideoid species with white or pale yellow thalli by having apothecia mostly under 0.5 mm in diam. and by lacking usnic acid.
Type: Australia. Exact locality unknown, original label data: “Ad saxa arenaria Novae Hollandiae” (= on sandstone in New Holland), sine dato, Hofstetter, F. 25 [L 910.134-2202–lectotype selected by Hertel (1973)].
Description.Thallus saxicolous, thick, contiguous, rimose-areolate, fissures with undulating to barely crenate edges, closely adjoining but not interlocked; surface white to creamish beige, smooth, epruinose to roughened, lacking soredia; prothallus consisting of a thin compact, blackened line, most pronounced where different thalli meet, occasionally extending between the areoles and thus discoloring the margins. Apothecia sparse to numerous, circular, cryptolecanorine, immersed, not emerging, with a plane to slightly depressed, epruinose disc, margin not to barely differentiated from the surrounding thallus, 0.1–0.8(–0.8) mm in diam.; hymenium hyaline, not inspersed, epihymenium with diffuse aeruginose pigment (cinereorufa-green: intensifying in K, HCl+ bluish green, N+ reddish violet), lacking crystals (gangaleoides-type); proper exciple thin, rarely moderately developed, apically olivaceous due to a mixture of a brown pigment (elachista-brown: dissolving in K, HCl± dull greenish, N−) and an aeruginose pigment (cinereorufa-green), basally reddish brown (elachista-brown), occasionally with few large crystals that do not dissolve in K; thalline exciple not clearly differentiated from surrounding thallus; hypothecium hyaline to pale yellowish (intensifying in K); ascospores 8/ascus, simple, broadly ellipsoid to subglobose, (5.9–)6.7–8.1(–8.9) × (4.0–)4.6–5.7(–5.9) μm (n = 50). Pycnidia not seen [according to Ryan et al. (2004): immersed, conidia filiform, 10–16 × ca. 0.8 μm].
Ecology and distribution. Widely distributed in subtropical to tropical, or even temperate regions (North and South America, Africa, Asia, Australasia, Oceania), new to Ecuador and the Galapagos; from the coastal zone through the dry into the transition zone, apparently absent from the humid zone, but re-appearing again in the upper dry zone; mostly in open habitats, on ±exposed, sunny rock, rarely semi-shaded and ±sheltered.
Notes. This saxicolous species is morphologically very similar to L. subimmersa, but it does not contain zeorin and unlike L. subimmersa ssp. ramboldii, always lacks xanthones. The apothecial discs are also diagnostic as they are always partially blackened by cinereorufa-green, an olive green, N+ reddish violet pigment which is absent in the similar L. legalloana (microscope!). Unlike L. legalloana and L. subimmersa, the thalline areoles of L. oreinoides are undulate to crenate, but are not tightly interlocked by serrate margins.