Type: Dominica. Saint Mark Parish: Souffrière, 2-Jul-1892, Elliott, W.R. s.n. (TUR-Vain 05078–lectotype selected by Elix & Øvstedal 2007).
Description. Thallus saxicolous, thick, contiguous, rimose-areolate, fissures with distinctly crenate to strongly serrate, tightly interlocking edges; surface white to creamish beige, smooth to ±roughened, epruinose, lacking soredia; prothallus a thin compact, blackened line, most pronounced where different thalli meet. Apothecia sparse to numerous, circular, 0.1–1 mm in diam., cryptolecanorine, immersed, not emerging, with a plane to slightly depressed, epruinose disc, margin not to barely differentiated from the surrounding thallus; hymenium hyaline, not inspersed, epihymenium lacking crystals, with a diffuse reddish brown pigment (arnoldiana-brown: K+ dull brown, HCl+ reddish brown, N−), pigment persistent in K (glabrata-type); proper exciple thin, rarely moderately developed and then with a diffuse reddish brown pigment (arnoldiana-brown), with few crystals; thalline exciple barely differentiated from surrounding thallus, with few large crystals that do not dissolve in K (pulicaris-type); hypothecium hyaline to pale yellowish (intensifying in K); ascospores 8/ascus, simple, narrowly ellipsoid to ellipsoid, rarely subglobose, (6.9–)8.1–11.0(–12.9) × (4.0)4.7–5.9(–5.9) μm (n = 40). Pycnidia not seen.
Chemistry. Thallus cortex P+ yellow, K+ yellow, KC–, C–, UV–, medullary reactions identical with the thallus surface except where pigmented orange, the pigment K+ purple; containing atranorin [major], skyrin [major], zeorin [major], leucotylin [minor], and unknown terpenes [minor]; [specimens analyzed with TLC: Bungartz, F. 4823 (CDS 28989), 4876 (CDS 29075), 5639 (CDS 33264)]. In the protologue Øvstedal & Elix (2007) did not mention zeorin or leucotylin, two secondary metabolites regularly found in Galapagos specimens. Instead Øvstedal & Elix (2007) report additional rugulosin, diploicin and 4,5-dichlorolichexanthone, none of which were found in the present specimens.
Ecology and distribution. New to Ecuador and the Galapagos, originally described from the Caribbean (French Antilles: Guadeloupe, Dominica and St. Vincent); a common saxicolous species, often growing with L. austrosorediosa, L. prosecha, L. subimmersa and Caloplaca diplacia, in similar habitats, close to the ground, dust-rich and ±nitrophytic.
Notes. Specimens of L. legalloana are distinguished from the superficially similar L. subimmersa by their content of skyrin, a deeply orange, K+ purple anthraquinone, always present in the lower medulla but sometimes sparse and in low concentrations (then only detected by spot tests or even TLC), occasionally more extensive and penetrating the entire medulla, very rarely reaching the upper surface and disfiguring it with conspicuous, deep orange spots. Lecanora prosecha, the only other Lecanora species on Galapagos with skyrin can be distinguished by the presence of arthothelin. Lecanoraoreinoides is also very similar but this species has jet-black apothecia and thalline areoles with undulate but not distinctly serrate margins; it produces confluentic acid but lacks skyrin.