Revision of the Lichen Genus <i>Stereocaulon</i> (Stereocaulaceae, Ascomycota) in South Korea

Lichen genus <i>Stereocaulon</i> (Schreb.) Hoffm is distributed throughout the world. Although 15 <i>Stereocaulon</i> species have been recorded in Korea, no detailed taxonomic or revisionary research has been conducted for nearly two decades. In this study, we collected 260 putative <i>Stereocaulon</i> spp. samples and identified the species based on morphological, chemical, and molecular characteristics. From the collected samples, 10 species of <i>Stereocaulon</i> were identified, nine of which had already been reported, although this was the first report for the tenth, <i>S</i>. <i>octomerellum</i> Hue, in Korea. General characteristics of <i>Stereocaulon</i> spp. include coralloid phyllocladia and tubercular cephalodia; however, the specimen first collected in Korea was a rare species with tomentum on the pseudopodetia. The specimen of <i>S. octomerellum</i> is characterized by the presence of a primary thallus, granule to short coralloid phyllocladia, and pseudopodetia up to 1 cm in size, with tubercular cephalodia. To determine the phylogeny of the specimens, we compared the ITS sequences of ribosomal DNA and the β-tubulin gene sequences. Phylogenetic analysis showed that the Korean <i>Stereocaulon</i> species were monophyletic and placed in the previous phylogenetic classification. Species of <i>S. intermedium</i> and <i>S. exutum</i>, however, were polyphyletic, and are morphologically variable and widespread species. Overall, we present here detailed morphological and chemical descriptions of each species identified and a revised key of all known <i>Stereocaulon</i> species in South Korea.