Usnea subdasaea Truong & P.Clerc The Bryologist114(3): 499-500 (2011).
Type: ECUADOR. Galápagos, Isla Isabela, Volcán Sierra Negra, road to Sierra Negra crater, close to La Esperanza, 0°51.0'37.9''S, 91°1.0'40.0''W, 306 m alt., humid zone, farming areas, slope 20° SE, on living fencepost, 15-Aug-2008, Truong 1194 [holotype in CDS (39505); isotypes in G and UPS]. %C/M/A: 5/30/30. Chemistry: usnic, salazinic, galbinic, norstictic acid.
For a detailed description see Truong et al. (2011).
Short Description. Usnea subdasaea is one of several Galapagos species with an orange subcortical pigmentation in the medulla. The species is characterized by irregular branches that are ±inflated and constricted at their attachment point, and by numerous fibrils and isidiofibrils densely confined into distinctly delimited areas on the branch surface.
Usnea dasaea has a very similar morphology and chemistry, but differs by the absence of medullary pigmentation and it lacks isidiofibrils. Fibrils of U. dasaea also tend to be thicker and more spinulose. Usnea grandisora (also with salazinic, galbinic and norstictic acid) can be distinguished by much larger soralia, often encircling the whole branch, then becoming deeply excavate, and by a much thicker cortex. Usnea subcornuta differs in both chemistry and morphology.
Chemistry. Medulla of most specimens with salazinic, galbinic, and norstictic acid [P+ yellow to orange, K+ yellow turning deep red or orange (±crystals), C–, KC–]; few specimens contain only unidentified tri-terpenoids [spot tests negative].
Ecology and distribution. Known from the Neotropics (Bolivia, Colombia, Ecuador, Peru); the species was described in Truong et al. (2011) based on type material collected in the Galapagos. The authors nevertheless did not consider the species endemic to the archipelago, citing paratype specimens from the South American continent. In the Galapagos U. subdasaea (with a pigmented medulla) is distinctly more common than the similar U. dasaea (with a white medulla). Both species are most frequently found in open habitats of the transition and humid zone, rarely also the dry zone. However, in Galapagos U. subdasaea covers a slightly broader altitudinal range, also present in the high-altitude dry zone; the species grows on bark (including cacti) and wood (fencepost), and has been found both on native and introduced trees.