Two in, one out: A comprehensive phylogeny of the tribe Elsholtzieae (Nepetoideae, Lamiaceae) sheds new light on its generic delimitation

Abstract

Elsholtzieae, the smallest tribe of the subfamily Nepetoideae (Lamiaceae), consists of approximately 70 species within eight genera. The tribe is primarily distributed across East and Southeast Asia, with China, Korea, and Japan representing the center of its diversity. Previous studies have indicated the polyphyly of Keiskea and Elsholtzia; however, due to the limited sampling and the use of only a few DNA markers, the relationships within and between the genera of Elsholtzieae remain unsatisfactorily understood. In this study, we present the most comprehensive phylogenetic analyses of Elsholtzieae to date, utilizing five chloroplast markers (matK, ndhF, rbcL, trnL-F, ycf1) and two nuclear regions (ITS, ETS). Our results confirm the monophyly of Elsholtzieae, which are resolved into five major clades, while at the same time confirming the non-monophyly of Keiskea, Elsholtzia, and possibly Perilla. Consequently, based on the molecular phylogenetic analyses combined with morphological and geographical evidence, we propose an expanded circumscription of the genus Perilla to include Keiskea and Mosla, and reinstate the genus Paulseniella to accommodate three species traditionally included in Elsholtzia. The newly recognized Elsholtzia s.str. is monophyletic with five well-supported lineages, while further work is needed to fully clarify its infrageneric classification. Furthermore, we provide an identification key for all the genera of Elsholtzieae reflecting these taxonomic changes, and checklists of Paulseniella and Perilla.