Molecular phylogeny and biogeography of Lophanthus and its allies (Lamiaceae)

As one of the taxonomically complicated groups of the subfamily Nepetoideae (Lamiaceae), the Hymenocrater+Lophanthus+Marmoritis clade (Lophanthus s.l. clade) consists of approximately 40 species distributed from eastern to southwestern Asia. Due to the sparse taxon sampling, previous molecular and morphological studies have not been capable of rendering the phylogenetic position of this clade and relationships of its taxa. We performed a comprehensive molecular study of the Hymenocrater+Lophanthus+Marmoritis clade, including an extensive taxon sampling, using nrDNA (ITS and ETS) and cpDNA (trnL-trnF, rps16, and rpl32-trnL) sequences. Bayesian and maximum likelihood approaches were used to reconstruct the phylogenetic relationships, dating of diversification, and historical biogeography of this clade. Although the present study confirms the polyphyly of Hymenocrater, Lophanthus and Marmoritis, the phylogenetic results do not confirm the unity of Lophanthus and its allies with Nepeta. Therefore, the generic delimitation of Lophanthus s.l. and Nepeta is yet to be determined, requiring an examination and assessment of adding a large number of Nepeta species and their close relatives. Our results also indicate the need to redefine Lophanthus sensu Budantsev more broadly as Lophanthus s.l. by synonymizing Hymenocrater and Marmoritis within Lophanthus. Two morphological synapomorphies, i.e., the resupinate corolla and an annulate hairy calyx tube in the middle or throat, support this unity. Dating and biogeographical analyses confirm that Lophanthus s.l. originated in the eastern Irano-Turanian floristic region in the late Miocene and later migrated to the central part of this region.