Usnea brasiliensis (Zahlbr.) Motyka Lich. Gen. Usnea Monogr. 2: 486 (1937). Usnea bornmülleri var. brasiliensis Zahlbr., Denkschrift. Math. Naturw. Classe Kais. Akad. Wiss. Wien 83: 183, 187 (1909)
Short Description. A detailed description of this species can be found in Herrera-Campos et al. (2001) and Herrera-Campos (2016). Clerc (2007) suggested that the taxon may better be treated as a subspecies of Usnea cornuta, but Truong et al. (2013a) demonstrated that the two taxa are genetically distinct and we therefore here treat them as separate species. Galapagos specimens show the clear characteristics of U. brasiliensis: the specimens contain protocetraric acid, their thalli are generally stouter and more rigid than U. cornuta, have a comparatively thinner axis and a broad, laxer medulla, their branches are more inflated and segmented, almost “sausage-like”. This contrasts with the more common phenotype of U. cornuta s.str., where the Galapagos specimens with stictic and/or salazinic acid consistently have branches not so inflated or segmented and the thalli are not as rigid, with a comparatively thicker axis and a medulla not quite as lax.
Ecology and distribution. New to Galapagos; Clerc (2007) considers the taxon (as U. cornuta ssp. brasiliensis) to be restricted to North and South America, but Pérez-Vargas et al. (2010) report U. brasiliensis also from Macaronesia, its distribution thus reaching across the Atlantic. In the Galapagos records are so far known only from the humid zone of Isabela, where the specimens have been found on native or introduced trees, fern-fronds, and on rock.