VAGRANT LICHENS IN NORTH-AMERICA

Vagrant lichen taxa are presently recognized in several genera. Xantho parmelia contains the largest number of vagrant taxa and is the most w idely distributed geographically, with vagrant taxa represented in sev eral habitats in North America and other continents. Aspicilia has the second largest number of vagrant taxa worldwide, including A. fruticu losa (Eversm.) Flagey, reported new for North America from Idaho, Mont ana, Oregon, Utah, and Wyoming. Habitat supporting vagrant lichens is typically windswept, semi-arid, and sparsely vegetated. In some areas attached, erratic, and vagrant taxa of Rhizoplaca occur sympatrically. Environmentally modified erratic forms of attached taxa of Dermatocar pon, Lecanora, and Umbilicaria occur in habitats occupied by vagrant t axa. Reproduction in vagrant lichens is typically by large unspecializ ed vegetative fragments. Due to widescale land disturbance, livestock grazing, and the dispersal strategies of vagrant lichens, some taxa ar e so fragmented in their distribution that they may become extinct.