Abstract

Usnea species with a red-orange cortical or subcortical pigmentation were studied in the tropical Andes (Venezuela, Colombia, Ecuador, Peru and Bolivia) and the Galapagos Islands. Sixteen species are treated, 14 occurring in the Andes and six in the Galapagos. Usnea crocata, U grandisora (endemic to the Galapagos), U. rubricornuta and U subdasaea are newly described. Usnea dorogawensis, michauxii, U. subcornuta and U subrubicunda are new to South America. Tri-terpenoids detected by thin layer chromatography play an important role in the taxonomy of this group of species. Several species were found both in the Andes and the Galapagos, and the diversity of species integrates elements from North America, tropical Africa, Macaronesia and even Asia. This emphasizes the importance of examining large geographic areas to better understand global distribution patterns in this cosmopolitan genus.