Zengfu Bai

During a taxonomic revision of the genus Meehania (Lamiaceae), we re-evaluated the identity and nomenclatural status of Meehania faberi (Hemsley) C. Y. Wu. The protologue cited two specimens without designating a holotype; further study revealed that these specimens represent two distinct species. Therefore, in this paper, we designate a lectotype for Meehania faberi (Hemsl.) C. Y. Wu, provide a description of the new species, and assign it the name M. triangularis. The lectotypification of M. faberi and the recognition of M. triangularis clarify a long-standing nomenclatural and taxonomic confusion in the genus Meehania.

Meehania porphyrea, a new species of Meehania, was discovered during extensive field surveys in the Xiaolongshan National Nature Reserve in Gansu, China. This region is located in the Qinba Mountains of southern Gansu, one of the province's biodiversity hotspots, where the complex environment creates diverse habitats for a wide variety of plant species. Morphologically, M. porphyrea resembles Meehania fargesii (H. Lév.) C. Y. Wu, but the former is distinguished by its overall smaller plant size, often purple abaxial leaf surfaces, pale bluish purple flowers, smaller corolla, and narrow tubular calyx. Based on these distinct characteristics, we describe it here as a new species.

Hybridization and polyploidization have given rise to complex cytonuclear conflicts and morphological continuity within the Asian Buddleja group, posing challenges in species delimitation and the assignment of conservation efforts. This study employed an integrative approach, utilizing morphological comparisons, ploidy estimations and phylogenomic insights to investigate the taxonomy of B. purdomii, previously treated as a synonym of B. brachystachya, and to describe two new species, B. atropurpurea and B. calostachya. A comprehensive phylogenetic analysis was conducted using whole plastid genomes and a large number of low‐copy nuclear genes assembled from genome skimming data from 61 samples, covering all the known Asian Buddleja species. Additionally, a population genetic analysis of B. lindleyana and B. atropurpurea was performed to further confirm whether B. atropurpurea is a distinct taxon from B. lindleyana. The ploidy level of each of the three species studied in depth was determined through chromosome counts, and morphological comparisons were made between the two putative new species with their sister relatives. The time of divergence of each species was estimated by dating of the maternally inherited plastomes. Phylogenetic reconstruction combined with morphological measurements confirmed the distinct taxonomic status of B. purdomii, B. atropurpurea, and B. calostachya. The times of divergence between these putative species and their sister taxa are estimated to be 10.7 Ma, 3.6 Ma, and 2.1 Ma, which may correspond to the intensification of the East Asian Summer Monsoon (EASM), the Qingzang movement and the Quaternary climate upheaval, respectively. This study sheds new light on species delimitation and the speciation process in Asian Buddleja, and also provides a robust taxonomic framework for the conservation and utilization of these species.