Hye One KimP, Joo-Hwan Kim

Department of Life Sciences, Gachon University, 1342 Seongnamdaero, Seongnam-si, Gyeonggi-do, Republic of Korea

The East Asia–North America disjunction is a well-known biogeographic pattern that provides important insights into plant origins, dispersal, and evolutionary history. The subfamily Medeoloideae (Liliaceae Juss.), comprising the two genera Clintonia Raf. and Medeola Gronov. ex L., represents a classic example of this intercontinental disjunction. In this study, we investigated the phylogenetic relationships and evolutionary history of Medeoloideae using plastid and nuclear genomic data based on 78 plastid protein-coding genes and the Angiosperms353 loci dataset. Phylogenetic analyses strongly supported the monophyly of Medeoloideae and recovered Clintonia and Medeola as well-supported sister genera, with western North American, eastern North American, and East Asian Clintonia forming distinct clades. Divergence-time analyses estimated the origin of Medeoloideae in the Eocene (ca. 37–40 Mya) and the diversification of Clintonia in the late Miocene (ca. 5–8 Mya). This temporal framework coincides with periods of repeated connectivity between North America and East Asia via the Bering Land Bridge, highlighting its potential role in shaping the intercontinental distribution of Clintonia. Subsequent lineage diversification on the two continents was likely shaped by contrasting paleoclimatic and geomorphological histories, as well as by Quaternary climatic fluctuations. By integrating plastid and nuclear genomic data, this study clarifies the phylogenetic placement and evolutionary trajectory of Medeoloideae and provides new insights into the origin and evolutionary history of East Asia–North America disjunct lineages within Liliaceae.