Usnea flammea Stirt.
Scott. Natural. 6: 102 (1881).

Short Description. For a detailed description see Clerc (1987) and Clerc (2011a); the species is distinguished by a short, erect-shrubby thallus with a pale trunk with distinct annulations, typically extending along the basal branches. The species is further characterized by small, enlarging soralia that bear short isidiomorphs. It has a relatively smooth surface, lacking (or with very scarce) papillae or tubercles. In section the cortex appears mat, the medulla is compact to dense and contains stictic and lobaric acid. Branches of U. flammea are cylindrical to slightly inflated and constricted at their ramification. Both U. cornuta and U. flammea might share the same chemistry (stictic acid gr.) but U. cornuta has a cortex that, in section, appears glossy, its trunk and basal branches are usually not annulated and the soralia are different. Usnea subcomplecta has a different chemistry (salazinic acid), abundantly tuberculate branches and a distinctly blackened base.

Chemistry. Medulla with stictic, norstictic and ± lobaric acid [P+ deep orange, K+ yellow slowly turning orange (crystals), C–, KC–].

Ecology and distribution. New to South America; this species was previously known from highly oceanic sites in coastal and Mediterranean Europe and Macaronesia; it was also recently reported from North America (Clerc & May 2007, Herrera-Campos 2016, McMullin & Wiersma 2017); the new report from the Galapagos is based on a single saxicolous specimen found in an agricultural area of the humid zone.