Usnea dorogawensis Asahina J. Jpn. Bot.28: 228 (1953).
Short Description. Detailed descriptions and illustrations are available in Ohmura (2001) and Truong et al. (2011). This minute species is characterized by extremely short, erect-shrubby thalli with inflated branches constricted at their ramification, bearing large and excavate soralia that lack isidiomorphs. The cortex surface is smooth, it lacks papillae or tubercles and appears thin and shiny in section. Specimens have a loose, thick medulla (A/M-ratio < 0.75) with an orange, subcortical pigmentation.
Chemistry. Medulla with lobaric and norstictic acid [P+ yellow, K+ yellow turning orange-red (crystals), C–, KC–]. Galapagos specimens correspond to a chemotype with lobaric and norstictic acid, while specimens from the tropical Andes (as well as the type from Japan) are characterized by lobaric and stictic acid.
Ecology and distribution. This species, previously known only from Japan (Ohmura 2001), was first reported from South America by Truong et al. (2011), at that time based on a single specimen collected in the Galapagos [Truong 1218 (CDS 39529)]. It has since also been found in continental South America (Truong & Clerc 2016: Colombia, Peru). Here we provide additional records for the Galapagos; all records are from the humid zone of Volcán Sierra Negra, on Isabela Island, mostly collected close to the ground, often on ferns or small shrubs. The minute thalli can easily be overlooked and the species is possibly more common than these few collections suggest.