This study investigated six taxa of the genus Eupatorium in Korea—E. chinense, E. lindleyanum, E. fortunei, E. tripartitum, E. japonicum, and E. makinoi—through a comprehensive review of protologues, examination of type specimens, assessment of ex...
This study investigated six taxa of the genus Eupatorium in Korea—E. chinense, E. lindleyanum, E. fortunei, E. tripartitum, E. japonicum, and E. makinoi—through a comprehensive review of protologues, examination of type specimens, assessment of external morphology, and molecular phylogenetic analyses based on the nuclear ITS region, with the aim of elucidating taxonomic boundaries among the taxa and reassessing nomenclatural issues. Morphological analyses revealed that stem pubescence, leaf shape and lobation, venation patterns, development of the petiole, glandularity of leaves and stems, capitulum and involucre morphology, the presence or absence of glandular trichomes on the corolla, and pappus length were informative characters for delimiting the taxa. Molecular phylogenetic analyses based on the ITS5–4 region using a Maximum Likelihood framework showed general concordance with morphological differentiation, with most taxa forming relatively distinct clades. In addition, this study clarified, for the first time in Korea, the taxonomic identity of E. fortunei and provided a diagnostic key along with detailed descriptions for each taxon.