Ji-Hyeon Jeon1#, Juhyun Park1#P, Woojin Seo1#, Jin-Oh Hyun2, Pan Li3, Yun Jiang4, Seung-Chul Kim1

1Department of Biological Sciences, Sungkyunkwan University, Suwon, Korea;
2Northeastern Asia Biodiversity Institute, Hanam, Korea;
3College of Life Sciences, Zhejiang University, Hangzhou, China;
4Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, China

#These authors contributed equally to this study

The genus Leuzea DC. (=Rhaponticum Ludwig; Cardueae; Asteraceae) is notorious for its intricate taxonomic boundary and controversial infrageneric classification. Of approximately 30 species recognized in the genus, only two species have been recorded in East Asia: L. uniflora (L.) DC. and L. chinensis (S. Moore) Susanna. A recent investigation reported a new occurrence of L. chinensis in the Korean Peninsula, while this species has been previously considered endemic to China. This novel finding led us to propose three alternative hypotheses to explain the disjunct distribution of L. chinensis between Korea and China: 1) homoplasy between two distinct lineages; 2) vicariance of a lineage through paleoclimatic and paleogeographic changes in East Asia; and 3) dispersal from widely distributed Chinese populations to a narrowly confined Korean population. To resolve the phylogenetic relationships among L. chinensis populations and elucidate the origin of the Korean population, we assembled nuclear ribosomal and chloroplast genomic sequences using a genome- skimming approach. Phylogenetic analyses based on both nuclear and chloroplast data inferred a close relationship between the two East Asian Leuzea species and strong monophyly of L. chinensis, making the homoplasy hypothesis less plausible. The robust monophyly of geographically disjunct L. chinensis populations rather suggested scenarios involving either ancestral/recent dispersal or vicariance. Ongoing studies will further dissect the genomic signature of two mutually exclusive hypotheses, ultimately clarifying the taxonomic delimitation and evolutionary trajectory of the Korean L. chinensis population.