Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Thallus: shrubby-erect to subpendant, 2-15 cm long branching: isotomic- to anisotomic-dichotomous basal part: paler or of the same color as main branches, without conspicuous cracks branches: tapering or irregular; lateral branches: often slightly to distinctly narrowed at attachment points, not or slightly to conspicuously foveate and/or transversally furrowed segments: terete or slightly ridged, cylindrical papillae: absent tubercles: absent fibercles: present, mainly main branches fibrils: 1-2(-3) mm, usually conspicuous, spinulous, easily breaking away, usually densely disposed on some parts of the branches, especially close to the basal part, rarely on whole length of branches, giving spinulous appearance to this part of the thallus soralia: punctiform to slightly elliptic longitudinally (especially on terminal branches), raised, smaller than half the diameter of main branches where they arise mainly on fibercles; typically enlarged on apices where they mainly arise on cortex ab initio, appearing ±fusiform isidiomorphs: occurring on soralia, not blackened at tips cortex: thin (4-8%), glossy, not conspicuously cracked medulla: large, compact to dense, often internally pinkish pigmented axis: moderately thick, often peripherally pinkish pigmented Apothecia: not seen Spot tests: medulla K+ yellow turning red, C-, KC-, P+ orangish yellow Secondary metabolites: cortex with usnic acid; medulla with norstictic (major), galbinic (major) and salazinic (major) acids, or very rarely only with salazinic (major) and norstictic (major) acids or with psoromic acid (major). Substrate and ecology: mainly on bark, rarely on wood or rock, mainly coastal, between 0 and 500 m, on Quercus spp., Pinus spp. in oak-pine forests or on diverse scrubs in the chaparral World distribution: world-wide, North and South America, Africa, Asia and Europe Sonoran distribution: southern California, Baja California, Chihuahua, and Sonora. Notes: This species can be recognized by its lateral branches constricted at ramification points, its numerous spinulous fibrils covering the branches, its minute soralia with isidiomorphs and the presence of galbinic acid in the medulla. Badly developed or old specimens with few fibrils may be difficult to separate from U. cornuta without investigation with t.l.c.
Short Description. This species is characterized by lateral branches of irregular diameter that are constricted at their ramification points, with numerous spinulose fibrils covering the branches or at least some parts of them, minute soralia bearing isidiomorphs, and the presence of galbinic acid in the medulla [for a detailed description see Clerc (2007) and Herrera-Campos (2016)]. According to Clerc (2007) poorly developed material may not have abundant fibrils. These specimens can then be difficult to separate from U. cornuta, a species that, however, does not contain galbinic acid and which can therefore reliably be distinguished by TLC.
Chemistry. Medulla with norstictic, galbinic, and salazinic acid [P+ yellow, K+ yellow turning deep red, C–, KC–]; from the Sonoran region Clerc 2007 also cites a chemotype that lacks galbinic acid, and another one with psoromic acid (not observed in the Galapagos).
Ecology and distribution:Usnea dasaea occurs worldwide, in North and South America, Africa, Asia and Europe; Truong et al. (2011) briefly mentioned that U. dasaea can also be found in Galapagos. The species is moderately common in the archipelago; it is one of few Usnea species that are more common in the humid zone and less frequently grow in the transition zone; a single specimen has also been found in the dry zone. All Galapagos specimens were found on bark of trees and shrubs.