Identity of Microtoena coreana (Lamiaceae), a doubtful species from Korea

The species Microtoena coreana has long been extremely doubtful. This species is endemic to South Korea, and only the holotype has been collected. The author, who described this species as new, placed it into the genus Microtoena without confidence. Some taxonomists even considered that it might belong to another genus instead of Microtoena. However, no conclusion has been achieved. In the present study, the holotype of Microtoena coreana was found and carefully examined. This holotype possesses 5-lobed corolla, broadly campanulate calyxes, and long-exserted stamens, which make it distinct from all the other species of Microtoena. The results of examination on a large number of specimens and statistical analysis of multiple characters clearly show that the holotype of Microtoena coreana is an element of Tripora divaricata (= Caryopteris divaricata). Therefore, the name Microtoena coreana is here excluded from the genus Microtoena, and is reduce to a synonym of Tripora divaricata. In addition, the lectotype of Tripora divaricata is designated in the present article