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Xanthoparmelia moctezumensis T. Nash
Family: Parmeliaceae
Xanthoparmelia moctezumensis image
Thallus: foliose, tightly adnate to adnate, 3-6 cm in diam., irregularly lobate lobes: subirregular, short, plane to subconvex, separate, contiguous to somewhat imbricate, 0.5-1.5 mm wide, not lobulate; apices: subrotund, smooth to crenate, eciliate upper surface: yellow-green, smooth, shiny, epruinose and emaculate, densely isidiate isidia: cylindrical, simple to rarely branched, 0.1-0.18 mm in diam., 0.1-0.4 mm tall; tips: weakly epicorticate, dull brown, occasionally erumpent; soralia and pustulae absent medulla: white, with continuous algal layer lower surface: pale brown, sparsely to moderately rhizinate; rhizines: pale brown, simple, 0.2-0.4 mm long Apothecia: not observed Pycnidia: not observed Spot tests: upper cortex K-, C-, KC-, P-; medulla K-, C-, KC+ yellow, P- Secondary metabolites: upper cortex with usnic acid (major); medulla with 3-α-hydroxybarbatic acid (major), barbatic acid (minor), baeomycesic and squamatic acids (both trace) and sometimes 4-O-demethylbarbatic acid (trace). Substrate and ecology: on acidic rocks, often in open, arid to woodland habitats World distribution: southwestern North America Sonoran distribution: occasional at lower elevations in Baja California Sur, Sinaloa and Sonora. Notes: Morphologically X. moctezumensis is very similar to X. ajoensis and both species contain substances from the diffractaic acid - barbatic acid chemosyndrome. They are undoubtedly closely related and are best separated by their secondary chemistry, the medulla of X. moctezumensis reacting KC+ yellow (3-α-hydroxybarbatic acid major) whereas the medulla of X. ajoensis is KC- (diffractaic acid major).