Two new hairy Leptogium (Collemataceae) species from western North America

Abstract. Leptogium bacatum is described as a new species with spherical-celled (moniliform) hairs and Leptogium umpquaense has matted, tangled hairs on the upper surface. Both are in the so-called section Mallotium. The species differ in morphology and DNA sequences from others in this group. We supplement existing GenBank data with new ITS and nuLSU sequences for 12 Leptogium specimens from Arizona, California, Mexico, New Mexico, Oregon, Nova Scotia and Ontario. Leptogium bacatum is distinguished by a medium-sized thallus, lobes to 6 mm wide, with long, distinct longitudinal wrinkles so that lobes look stretched, a lower surface covered with short (to 40 µm), fine, spherical-celled tomentum, numerous laminal and marginal lobules and granular to cylindrical isidia. The known range is northern California and New Mexico. Leptogium umpquaense has matted, tangled white hairs on the upper and lower surfaces and produces prolific coralloid to flattened isidia in dense groups along the margins, giving the thallus the look of a cauliflower. We provide a key to the Leptogium species known from western North America.