Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: very variable, totally leprose throughout as a loose mass of irregular lumps of soredia, or stratified and at first usually forming rosettes, but later irregularly spreading, indeterminate and with or without obscure lobes, sometimes determinate and with well-developed lobes up to 0.9 mm wide with a raised margin, sometimes wrinkled and partly free from the substrate, up to 0.6 mm thick, up to several cm in diam. upper surface: shades of grayish yellow to greenish yellow, very rough soredia: coarse, usually ±globose and up to 0.3 mm in diam., sometimes forming irregular, flattened to elongate-terete lumps up to 0.7 mm in diam., without projecting hyphae except for marginal ones medulla: not evident to distinct and white lower surface: often pale brown (partly due to adhering particles), with scarse to abundant tomentum of colorless to brownish hyphae not visible from above Spot tests: K-, C-, KC-, P+ orange or P- Secondary metabolites: atranorin (trace; an uncommon accessory), pannaric acid 6-methyl ester (major), ±4-oxypannaric acid 6-methyl ester (in trace to moderate amounts; rarely absent), roccellic acid (a common accessory in trace amounts), 4-oxypannaric acid 2-methyl ester (tr.), pannaric acid (tr.), pannaric acid 2-methyl ester (tr. to minor), methyl prophyrilate (tr. to minor), porphorilic acid (tr.), lecanoric acid (trace; found in a few specimens due to a contaminant?). Substrate and ecology: on rocks, soil, mosses, detritus, bark (Quercus gambelii), and Selaginella on cliff-faces, in sheltered crevices, under overhangs, in boulder cracks World distribution: Africa, Australia, Europe, New Zealand, and North and South America Sonoran distribution: Arizona, Sonora, and Baja California at 670-3000 m.
Thallus saxicolous; placodioid leprose, i.e., developing upon a common, shared hypothallus, prothallus fine, inconspicuous, main thallus distinctly delimited, but lacking a conspicuously ‘crisped’ lip (close, but not identical to the xerophila-type sensu Lendemer 2011a); surface deep yellow to brownish yellow, pale beige only along the margin and where the surface gets eroded; hypothallus inconspicuous, exposed only as a fine prothallus along the thallus margin or where granules on the surface have eroded; rhizohyphae absent or at least indistinct; granules pseudocorticate, very compact, coarse [(35–)40–70(–100) µm in diam., rather uniform in size], mature granules without conspicuous extruding hyphae, immature or damaged granules in eroded thallus parts rarely with few protruding hyphae; photobiont green, coccoid, 7–10 μm in diam.
Spot tests and chemistry: P+ reddish orange, K+ yellow orange, C−, KC−; UV-(dark); pannaric acid 6-methyl ester and accessories.
Distribution and ecology: Cosmopolitan (Saag et al. 2009); previously reported to Ecuador by Flakus et al. (2013), but new to Galapagos; on vertical to overhanging, but ±exposed rock surfaces, though typically facing south or east and thus shaded, not receiving direct sunlight.
Notes: The species is easily recognized by its deep brownish beige to yellowish color and the distinctly delimited thalli of densely packed, compact granules with a distinctly pseudocorticate surface. Following the key to the Lepraria growth types in Lendemer (2011a) the species keys out within the finkii-type, although the specimens have a distinctly different appearance from all other Galapagos Lepraria species with this growth morphology. Despite lacking a ‘crisped’ lip, as is present in the closely related L. sipmaniana (Kümmerl. & Leuckert) Kukwa (2002: 226), the granules of L. vouauxii are distinctly pseudocorticate and its thalli are well delimited, both characteristics not present in the finkii-type s.str. Based on these characters one might decide to regard its growth morphology as a distinctly separate type, but we prefer here to consider it to be a variation of the xerophila-type. Apparently the growth form of L. vouauxii can be quite variable. Lendemer (pers. comm.) reports that he has seen specimens of L. vouauxii growing close to the coast with a ±pseudocorticate appearance. He agrees that these specimens have more clearly delimited thalli that may better be accommodated in the xerophila- rather than the finkii-type.
The thalli of L. vouauxii often display a distinctive coloration pattern, with pale yellowish beige margins, deeper yellowish brown towards the center, and again pale yellowish beige or even whitish in the very center, where older parts have eroded.
Lepraria vouauxii not only looks quite different from the other species of Lepraria here assigned to the finkii-type, it is also chemically distinct. Due to the presence of dibenzofurans (in particular pannaric acid 6-methyl ester) it appears closely related to Lepraria tenella, a species that, like L. vouauxii and L. sipmaniana, has compact, pseudocorticate granules of similar size. However, the granules of L. tenella are pale yellowish to greenish white or ivory, not distinctly brown or beige, and soon branch into distinct pseudopodetia (see notes for that species).