Background A robust molecular phylogeny is fundamental for developing a stable classification and providing a solid framework to understand patterns of diversification, historical biogeography, and character evolution. As the sixth largest angiosperm family, Lamiaceae, or the mint family, consitutes a major source of aromatic oil, wood, ornamentals, and culinary and medicinal herbs, making it an exceptionally important group ecologically, ethnobotanically, and floristically. The lack of a reliable phylogenetic framework for this family has thus far hindered broad-scale biogeographic studies and our comprehension of diversification. Although significant progress has been made towards clarifying Lamiaceae relationships during the past three decades, the resolution of a phylogenetic backbone at the tribal level has remained one of the greatest challenges due to limited availability of genetic data. Results We performed phylogenetic analyses of Lamiaceae to infer relationships at the tribal level using 79 protein-coding plastid genes from 175 accessions representing 170 taxa, 79 genera, and all 12 subfamilies. Both maximum likelihood and Bayesian analyses yielded a more robust phylogenetic hypothesis relative to previous studies and supported the monophyly of all 12 subfamilies, and a classification for 22 tribes, three of which are newly recognized in this study. As a consequence, we propose an updated phylogenetically informed tribal classification for Lamiaceae that is supplemented with a detailed summary of taxonomic history, generic and species diversity, morphology, synapomorphies, and distribution for each subfamily and tribe. Conclusions Increased taxon sampling conjoined with phylogenetic analyses based on plastome sequences has provided robust support at both deep and shallow nodes and offers new insights into the phylogenetic relationships among tribes and subfamilies of Lamiaceae. This robust phylogenetic backbone of Lamiaceae will serve as a framework for future studies on mint classification, biogeography, character evolution, and diversification. Graphical abstract

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The tribe Phlomideae (Lamiaceae: Lamioideae) is divided into the three genera Phlomis, Phlomoides (incl. Pseuderemostachys, Lamiophlomis and Notochaete), and Eremostachys (incl. Paraeremostachys), contains about 278 species and has a distribution range extending from Europe to Mongolia, China, and India. Here, we present a phylogenetic analysis based on nuclear ribosomal (ITS) and cpDNA (partial trnK, rpl32-trnL, and trnT-A) sequence data of 56 accessions representing all genera and major subgeneric taxa of Phlomideae. Taxon sampling covered the genera Phlomoides and Eremostachys more intensively than previous phylogenetic investigations of the tribe. Parsimony and Bayesian analyses of each marker, as well as the combined plastid datasets, produced nearly congruent trees. Monophyly of Phlomis s.str. is confirmed here, although only few representatives of this genus were included. In all obtained trees a core group of Phlomoides and Eremostachys is strongly supported. In accordance with morphological evidence, molecular data confirm the inclusion of Eremostachys, Notochaete, and Paraeremostachys in Phlomoides. In conclusion, the number of recognized genera in Phlomideae is reduced to two: Phlomis and Phlomoides. The necessary new combinations are proposed.

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