A REVISION OF THE USNIC ACID-CONTAINING TAXA BELONGING TO LECANORA-SENSU-STRICTO (LECANORALES, LICHENIZED ASCOMYCOTINA)

Eighteen taxa belonging to the Lecanora subfusca group that contain us nic acid in addition to atranorin are revised on a worldwide basis. Th e following species are described as new: L. alba Lumbsch from Austral ia, L. floridula Lumbsch from Florida, L. formosula Lumbsch from Austr alasia, L. neonashii Lumbsch from Mexico, and L. transvaalensis Lumbsc h from South Africa. A xanthone containing population of L. wilsonii i s distinguished as L. wilsonii ssp. xanthophora Lumbsch. Lecanora achr oella and L. subflavicans are reduced to synonymy with L. achroa, and L. elatinoides var. straminea with L. elatinoides. A key to the taxa t reated is included. After consideration of the morphological, anatomic al, and chemical variation, it is concluded that the usnic acid contai ning species of Lecanora do not form a natural group and cannot be sep arated from Lecanora s. str.