Sticta torii sp. nov., a remarkable lichen of high conservation priority from northwestern North America

Sticta torii Simon & Goward sp. nov. is an isidiate lichen on Alnus, Malus and Picea branches in hypermaritime regions of northwestern North America. It is a rare species, currently known from only a few localities along a narrow longitudinal range in Southeast Alaska, British Columbia and Oregon. It differs from S. fuliginosa and S. sylvatica in its smaller, more irregular lobes and generally well-developed fringe of marginal isidia, and from S. beauvoisii in its smaller size, less elongate lobes and distinctly arbuscular to penicillate marginal isidia. Also diagnostic are the cyphellae, the basal portions of which bear cells with numerous papillae – a feature shared with a small group of closely allied neotropical species including the recently described S. arbuscula and S. arbusculotomentosa. These latter species, however, bear tomentum over the upper surface, unlike S. torii, which is glabrous.