Revision of the Lichen Genus Stereocaulon (Stereocaulaceae, Ascomycota) in South Korea

Lichen genus Stereocaulon (Schreb.) Hoffm is distributed throughout the world. Although 15 Stereocaulon 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 Stereocaulon spp. samples and identified the species based on morphological, chemical, and molecular characteristics. From the collected samples, 10 species of Stereocaulon were identified, nine of which had already been reported, although this was the first report for the tenth, S. octomerellum Hue, in Korea. General characteristics of Stereocaulon 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 S. octomerellum 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 Stereocaulon species were monophyletic and placed in the previous phylogenetic classification. Species of S. intermedium and S. exutum, 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 Stereocaulon species in South Korea.

地衣珊瑚枝属（Stereocaulon）(Schreb.) Hoffm 广泛分布于全球各地。尽管韩国已记录有15种珊瑚枝属物种，但近二十年来尚未开展过详细的分类学或修订研究。本研究共采集260份疑似珊瑚枝属物种的标本，并基于形态学、化学及分子特征完成物种鉴定。经鉴定，本次采集标本共涵盖10种珊瑚枝属物种，其中9种为韩国已有记录物种，第十种为首次在韩国报道的S. octomerellum Hue。珊瑚枝属物种的典型特征为珊瑚状叶状枝（phyllocladia）与瘤状头状体（cephalodia）；但本次在韩国首次采集的该类群标本为稀有物种，其假足状体（pseudopodetia）表面被有绵毛（tomentum）。八蕊珊瑚枝（S. octomerellum Hue）的鉴别特征为：具初生地衣体（primary thallus），叶状枝呈颗粒状至短珊瑚状，假足状体高达1厘米，且具瘤状头状体。为明确本次标本的系统发育关系，本研究比对了核糖体DNA的ITS序列以及β-微管蛋白（β-tubulin）基因序列。系统发育分析结果显示，韩国珊瑚枝属物种为单系群，且与此前的系统分类结果一致。但中间珊瑚枝（S. intermedium）与裸露珊瑚枝（S. exutum）为复系群，二者均为形态变异度高、分布广泛的物种。综上，本研究对本次鉴定出的所有珊瑚枝属物种提供了详细的形态学与化学特征描述，并修订了韩国已知珊瑚枝属物种的分类检索表。