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Abstract Background Arundinelleae is a small tribe within the Poaceae (grass family) possessing a widespread distribution that includes Asia, the Americas, and Africa. Several species of Arundinelleae are used as natural forage, feed, and raw materials for paper. The tribe is taxonomically cumbersome due to a paucity of clear diagnostic morphological characters. There has been scant genetic and genomic research conducted for this group, and as a result the phylogenetic relationships and species boundaries within Arundinelleae are poorly understood. Results We compared and analyzed 11 plastomes of Arundinelleae, of which seven plastomes were newly sequenced. The plastomes range from 139,629 base pairs (bp) (Garnotia tenella) to 140,943 bp (Arundinella barbinodis), with a standard four-part structure. The average GC content was 38.39%, but varied in different regions of the plastome. In all, 110 genes were annotated, comprising 76 protein-coding genes, 30 tRNA genes, and four rRNA genes. Furthermore, 539 simple sequence repeats, 519 long repeats, and 10 hyper-variable regions were identified from the 11 plastomes of Arundinelleae. A phylogenetic reconstruction of Panicoideae based on 98 plastomes demonstrated the monophyly of Arundinella and Garnotia, but the circumscription of Arundinelleae remains unresolved. Conclusion Complete chloroplast genome sequences can improve phylogenetic resolution relative to single marker approaches, particularly within taxonomically challenging groups. All phylogenetic analyses strongly support the monophyly of Arundinella and Garnotia, respectively, but the monophylly of Arundinelleae was not well supported. The intergeneric phylogenetic relationships within Arundinelleae require clarification, indicating that more data is necessary to resolve generic boundaries and evaluate the monophyly of Arundinelleae. A comprehensive taxonomic revision for the tribe is necessary. In addition, the identified hyper-variable regions could function as molecular markers for clarifying phylogenetic relationships and potentially as barcoding markers for species identification in the future.

Three new species of Isodon (Lamiaceae) from China are described and illustrated, based on both morphological evidence and our recent phylogenomic studies of the genus. Isodon attenuatus, a herbaceous new species known only from the Fanjing Mountain, is shown to be sister to I. villosus, but they can be easily distinguished by leaf and inflorescence indumentum, calyx teeth shape and corolla tube morphology. Isodon gongshanensis, a herbaceous new species collected from the Hengduan Mountains in southwest China, represents a distinct lineage within the genus. Isodon sukungii, a shrubby new species also endemic to the Hengduan Mountains, was previously misidentified as I. tenuifolius, but they are phylogenetically distantly related and differ in lamina size and margin, inflorescence type and corolla length and shape.

Salvia penghuana, a new species from Guizhou Province of southwestern China, is described and illustrated. Morphologically, Salvia penghuana is similar to S. filicifolia, but can be easily distinguished from the latter by ovate-lanceolate bracts, purple corolla, and foot-shaped fused lower arms of connective. In addition, S. penhuana is morphologically similar to S. cavaleriei, but differs by having 3–4-pinnate leave, ovate-lanceolate bracts, puberulent calyx, and longer upper arms of connective. Based on the fibril root, small calyx and corolla, and completely reduced posterior thecae, S. penghuana should be placed in section Sobiso of subg. Glutinaria.

Dracocephalum is a large genus comprises approximately 80 species of perennial herbs, mainly distributed in high elevation regions of temperate and Central Asia, with about half native to China. Within the genus, D. argunense and D. integrifolium are important herbs with great medicinal value. We sequenced plastomes of these two species for the first time. These plastomes showed a typical quadripartite structure and the length varied from 149,978 bp (D. integrifolium) to 150,802 bp (D. argunense). Plastomes of D. argunense and D. integrifolium included 127 and 133 genes, respectively. Phylogenetic analyses supported the monophyly of the redefined Dracocephalum and systematic relationships within the sampled species were well resolved. Our study added new genetic information about D. argunense and D. integrifolium and has great potential for further diversity studies, phylogenetic studies, and understanding of evolutionary history in Dracocephalum.

Phlomoides bomiensis, a new species in Bomi County, Xizang, China, was described and illustrated. In addition, Phlomoides longidentata, previously only known from Nepal and Bhutan, is newly recorded from Dingri County, Xizang, China. The phylogenetic placement of both species within the genus was analysed using nine plastid DNA markers (atpB-rbcL, psbA-trnH, rpl16, rpl32-trnL, rps16, trnK, trnL-trnF, trnS-trnG, trnT-trnL). Both species have brown-black trichomes inside the upper corolla lip and nested within the same subclade of Clade II. A diagnostic key to the Phlomoides species belonging to this subclade is provided.

Phlomoides, with 150–170 species, is the second largest and perhaps most taxonomically challenging genus within the subfamily Lamioideae (Lamiaceae). With about 60 species, China is one of three major biodiversity centers of Phlomoides. Although some Phlomoides species from China have been included in previous molecular phylogenetic studies, a robust and broad phylogeny of this lineage has yet to be completed. Moreover, given the myriad new additions to the genus, the existing infrageneric classification needs to be evaluated and revised. Here, we combine molecular and morphological data to investigate relationships within Phlomoides, with a focus on Chinese species. We observed that plastid DNA sequences can resolve relationships within Phlomoides better than nuclear ribosomal internal and external transcribed spacer regions (nrITS and nrETS). Molecular phylogenetic analyses confirm the monophyly of Phlomoides, but most previously defined infrageneric groups are not monophyletic. In addition, morphological analysis demonstrates the significant taxonomic value of eight characters to the genus. Based on our molecular phylogenetic analyses and morphological data, we establish a novel section Notochaete within Phlomoides, and propose three new combinations as well as three new synonyms. This study presents the first molecular phylogenetic analyses of Phlomoides in which taxa representative of the entire genus are included, and highlights the phylogenetic and taxonomic value of several morphological characters from species of Phlomoides from China. Our study suggests that a taxonomic revision and reclassification for the entire genus is necessary in the future.

Phlomoides is one of the largest genera of Lamiaceae with approximately 150–170 species distributed mainly in Eurasia. In this study, we describe and illustrate a new species, P. henryi, which was previously misidentified as P. bracteosa, from Yunnan Province, southwest China. Molecular phylogenetic analyses revealed that P. henryi is found within a clade in which most species lack basal leaves. In this clade, the new species is morphologically distinct from P. rotata in having an obvious stem and, from the rest, by having transparent to white trichomes inside the upper corolla lip. In addition, micro-features of trichomes on the calyx and leaf epidermis can differentiate the new species from other species grouped in the same clade and a key, based on trichome morphology for these species, is provided. The findings demonstrate that the use of scanning electron microscopy can reveal inconspicuous morphological affinities amongst morphologically similar species and play an important role in the taxonomic study of the genus Phlomoides.

Isodon xiaoluzhiensis, a new species of the tribe Ocimeae in family Lamiaceae, is described and illustrated. The new species is known only from the type locality, Xiaoluzhi village in Luzhijang dry-hot valley of Yimen County, central Yunnan, southwest China. It is characterized by having a procumbent habit, gracile stems and branches, relatively small leaves and flowers, and the phenology of flowering in winter. The morphological comparisons with its putative closest relatives (I. adenanthus and I. hsiwenii) are also presented.

Abstract The genus Salvia L. (Lamiaceae) comprises myriad distinct medicinal herbs, with terpenoids as one of their major active chemical groups. Abietane-type diterpenoids (ATDs), such as tanshinones and carnosic acids, are specific to Salvia and exhibit taxonomic chemical diversity among lineages. To elucidate how ATD chemical diversity evolved, we carried out large-scale metabolic and phylogenetic analyses of 71 Salvia species, combined with enzyme function, ancestral sequence and chemical trait reconstruction, and comparative genomics experiments. This integrated approach showed that the lineage-wide ATD diversities in Salvia were induced by differences in the oxidation of the terpenoid skeleton at C-20, which was caused by the functional divergence of the cytochrome P450 subfamily CYP76AK. These findings present a unique pattern of chemical diversity in plants that was shaped by the loss of enzyme activity and associated catalytic pathways.

The monotypic genus Pseudomarrubium is perhaps the most poorly understood taxon within the subfamily Lamioideae (Lamiaceae). While advances in molecular phylogenetics have clarified the phylogeny and taxonomy of Lamioideae, the systematic placement of Pseudomarrubium remains unclear, as it has never been tested using molecular phylogenetic analyses due to an inaccessibility of plant material. In this study, we used high-throughput next-generation sequencing to infer the systematic placement of Pseudomarrubium based on old herbarium collections as well as silica gel-dried leaves. Phylogenomic analyses demonstrate that Pseudomarrubium is a member of tribe Phlomideae and nested within Phlomoides, and a new combination, Phlomoides eremostachydioides, is proposed. The study highlights that herbarium-preserved samples, even very old ones, are invaluable resources that can be used to generate reliable genome-scale data and be used for molecular phylogenetic inquiries.

The indumentum of nutlets is shown to be of phylogenetic importance in previous molecular phylogenetic studies of Paraphlomis, a genus of Lamiaceae with approximately 30 species distributed mainly in southern China and Southeast Asia. Nearly half the species of Paraphlomis are known from limestone areas. In this study, we described and illustrated a new species, P. hsiwenii, from the karst mountain forests in Guangxi Zhuang Autonomous Region, China. Our molecular phylogenetic analyses revealed that P. hsiwenii is recovered in a clade consisting of species with hairy nutlets. The new species is morphologically most similar to P. pagantha from the same clade, but they differ in the morphology of lamina bases, length of pedicels and calyces, as well as the morphology of upper corolla lips.

As one of the largest genera of Lamiaceae and of great medicinal importance, Isodon is also phylogenetically and taxonomically recalcitrant largely ascribed to its recent rapid radiation in the Hengduan Mountains. Previous molecular phylogenetic studies using limited loci have only successfully resolved the backbone topology of the genus, but the interspecific relationships suffered from low resolution, especially within the largest clade (Clade IV) which comprises over 80% species. In this study, we attempted to further elucidate the phylogenetic relationships within Isodon especially Clade IV using plastome sequences with a broad taxon sampling of ca. 80% species of the genus. To reduce systematic errors, twelve different plastome data sets (coding and non-coding regions with ambiguously aligned regions and saturated loci removed or not) were employed to reconstruct phylogeny using maximum likelihood and Bayesian inference. Our results revealed largely congruent topologies of the 12 data sets and recovered major lineages of Isodon consistent with previous studies, but several incongruences are also found among these data sets and among single plastid loci. Most of the shallow nodes within Clade IV were resolved with high support but extremely short branch lengths in plastid trees, and showed tremendous conflicts with the nrDNA tree, morphology and geographic distribution. These incongruences may largely result from stochasticity (due to insufficient phylogenetic signal) and hybridization and plastid capture. Therefore, the uniparental-inherited plastome sequences are insufficient to disentangle relationships within a genus which has undergone recent rapid diversification. Our findings highlight a need for additional data from nuclear genome to resolve the relationships within Clade IV and more focused studies to assess the influences of multiple processes in the evolutionary history of Isodon. Nevertheless, the morphology of the shape and surface sculpture/indumentum of nutlets is of systematic importance that they can distinguish the four major clades of Isodon.

Paraphlomis is a genus of Lamiaceae with about 30 species distributed mainly in subtropical China. In this study, we carried out the first molecular phylogenetic analyses to elucidate the relationships within the genus based on two nuclear and four plastid DNA regions. Our results, which recovered a species of Matsumurella within Paraphlomis, indicate that the genus is not monophyletic. The two sections and most of the series previously described within the genus are also shown to be polyphyletic. Combining with morphological evidence, our study indicates that nutlet morphology rather than calyx morphology is of phylogenetic value for the infrageneric classification of Paraphlomis. Moreover, P. jiangyongensis, a new species from southern China, is here described, and P. coronata, formerly treated as a variety of P. javanica, is here resurrected as a distinct species within the genus.

Isodon brevipedunculatus, a new species from southern China, is described and illustrated. The phylogenetic position of the new species within the genus was analyzed based on two nuclear ribosomal DNA regions and an ingroup sampling of about 80% of Asian species of Isodon. The results show that I. brevipedunculatus is recovered in a clade that consists of species mainly with glandular mericarps and that are distributed in the Sino-Japanese region. Combining molecular and geographical evidence, our study reveals that I. brevipedunculatus is most closely related to Isodon amethystoides and Isodon bifidocalyx, but differs from the former in lamina shape, number of flowers per cyme, and peduncle length, and from the latter in lamina indumentum, calyx morphology, and corolla length.

Abstract 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

Mazus lanceifolius (Mazaceae) is a perennial herb with opposite leaves and endemic to central China that has not been collected for 130 years. Rediscovery of this enigmatic species in the wild allows for determination of its phylogenetic position within Mazaceae. Phylogenetic reconstruction of Mazaceae based on DNA sequences from four plastid markers (matK, rbcL, rps16 and trnL-trnF) and nuclear ribosome ITS consistently showed that Mazus was not monophyletic. Mazus lanceifolius is in the most basal clade within Mazaceae, as sister to the remaining species of three recognized genera Dodartia, Lancea and Mazus. These results support the separation of M. lanceifolius from Mazus as a new genus, which was established here as Puchiumazus Bo Li, D.G. Zhang & C.L. Xiang. Meanwhile, a collection from Shennongjia Forestry District of Hubei Province, China, misidentified as “M. lanceifolius” in previous molecular study, is here revealed to represent an undescribed species of Mazus, i.e., M. fruticosus Bo Li, D.G. Zhang & C.L. Xiang, sp. nov. Morphologically, Puchiumazus is clearly distinct from the other three genera by having quadrangular to somewhat ribbed stems, and obviously opposite leaves. In addition, we provide a taxonomic key to the four genera of Mazaceae.

Abstract Background Plastid gene loss and pseudogenization has been widely documented in parasitic and mycoheterotrophic plants, which have relaxed selective constraints on photosynthetic function. More enigmatic are sporadic reports of pseudogenization and loss of important photosynthesis genes in lineages thought to be fully photosynthetic. Here we report the complete plastid genome of Saniculiphyllum guangxiense, a critically endangered and phylogenetically isolated plant lineage, along with genomic evidence of reduced chloroplast function. We also report 22 additional plastid genomes representing the diversity of its containing clade Saxifragales, characterizing gene content and placing variation in a broader phylogenetic context. Results We find that the plastid genome of Saniculiphyllum has experienced pseudogenization of five genes of the ndh complex (ndhA, ndhB, ndhD, ndhF, and ndhK), previously reported in flowering plants with an aquatic habit, as well as the surprising pseudogenization of two genes more central to photosynthesis (ccsA and cemA), contrasting with strong phylogenetic conservatism of plastid gene content in all other sampled Saxifragales. These genes participate in photooxidative protection, cytochrome synthesis, and carbon uptake. Nuclear paralogs exist for all seven plastid pseudogenes, yet these are also unlikely to be functional. Conclusions Saniculiphyllum appears to represent the greatest degree of plastid gene loss observed to date in any fully photosynthetic lineage, perhaps related to its extreme habitat specialization, yet plastid genome length, structure, and substitution rate are within the variation previously reported for photosynthetic plants. These results highlight the increasingly appreciated dynamism of plastid genomes, otherwise highly conserved across a billion years of green plant evolution, in plants with highly specialized life history traits.

Hanceola is a genus of eight herbaceous species previously thought to be endemic to southern China. However, H. suffruticosa, a new species described here from China and Vietnam, differs from all other species of Hanceola by its subshrubby habit. It is also distinct in its shallowly bicrenate laminae and densely purplish glandular puberulent inflorescences. The morphological description, illustrations, and distribution of the new species are presented. A key to all species of Hanceola is also provided.

Paralamium (Lamiaceae) is a monotypic genus within the subfamily Lamioideae and has a sporadic distribution in subtropical mountains of southeast Asia. Although recent studies have greatly improved our understanding of generic relationships within Lamioideae, the second most species-rich subfamily of Lamiaceae, the systematic position of Paralamium within the subfamily remains unclear. In this study, we investigate the phylogenetic placement of the genus using three datasets: (1) a 69,276 bp plastome alignment of Lamiaceae; (2) a five chloroplast DNA region dataset of tribe Pogostemoneae, and (3) a nuclear ribosomal internal transcribed spacer region dataset of Pogostemoneae. These analyses demonstrate that Paralamium is a member of Pogostemoneae and sister to the monotypic genus Craniotome. In addition, generic-level phylogenetic relationships within Pogostemoneae are also discussed, and a dichotomous key for genera within Pogostemoneae is provided.

The complete cp genome of Salvia trijuga Diels was 151,345 bp in length, including a large single-copy region (LSC) of 82,577 bp, a small single-copy region (SSC) of 17,584 bp and a pair of inverted repeats (IRs) of 25,592 bp. The genome contained 132 genes, including 87 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. The overall GC content of this genome was 37.9%, with the corresponding values of LSC, SSC and IR regions being 36.0%, 31.7% and 43.1%, respectively. Further, the phylogenomic analysis strongly supported the sister relationship of Salvia trijuga and Salvia plebeia R. Br.

Sect. Drymosphace is one of eight sections of Salvia subg. Glutinaria and includes 13 species and one dubious species that hold great economic value. Although the section is well supported, interspecific relationships remain unresolved. Moreover, most of this section’s plastome information remains unknown. In this study, we sequenced and assembled eight sect. Drymosphace plastomes and conducted comparative analyses within this section. The length of plastid genome sequences ranged from 151,330 bp to 151,614 bp, with 80 protein-coding, 30 tRNA, and four rRNA genes being annotated. The plastomes were found to be as conservative as other Lamiaceae species, showing high consistency and similarity in terms of gene content, order, and structure. Within the sect. Drymosphace, single-copy regions were more variable than IR regions, and the intergenic regions were more variable than the coding regions; nine hypervariable regions were detected, and some of them may be useful for the phylogenetic analysis of Salvia. The topologies inferred from all of the data sets indicated that sect. Drymosphace was monophyletic and that S. honania was sister to S. meiliensis. Compared to previous studies involving more sect. Drymosphace species, phylogenomic analyses can improve the phylogenetic resolution considerably.

The increased availability of large phylogenomic datasets is often accompanied by difficulties in disentangling and harnessing the data. These difficulties may be enhanced for species resulting from reticulate evolution and/or rapid radiations producing large-scale discordance. As a result, there is a need for methods to investigate discordance, and in turn, use this conflict to inform and aid in downstream analyses. Therefore, we drew upon multiple analytical tools to investigate the evolution of Micranthes (Saxifragaceae), a clade of primarily arctic-alpine herbs impacted by reticulate and rapid radiations. To elucidate the evolution of Micranthes we sought near-complete taxon sampling with multiple accessions per species and assembled extensive nuclear (518 putatively single copy loci) and plastid (95 loci) datasets. In addition to a robust phylogeny for Micranthes, this research shows that genetic discordance presents a valuable opportunity to develop hypotheses about its underlying causes, such as hybridization, polyploidization, and range shifts. Specifically, we present a multi-step approach that incorporates multiple checks points for paralogy, including reciprocally blasting targeted genes against transcriptomes, running paralogy checks during the assembly step, and grouping genes into gene families to look for duplications. We demonstrate that a thorough assessment of discordance can be a source of evidence for evolutionary processes that were not adequately captured by a bifurcating tree model, and helped to clarify processes that have structured the evolution of Micranthes.

Scutellaria, or skullcaps, are medicinally important herbs in China, India, Japan, and elsewhere. Though Scutellaria is the second largest and one of the more taxonomically challenging genera within Lamiaceae, few molecular systematic studies have been undertaken within the genus; in part due to a paucity of available informative markers. The lack of informative molecular markers for Scutellaria hinders our ability to accurately and robustly reconstruct phylogenetic relationships, which hampers our understanding of the diversity, phylogeny, and evolutionary history of this cosmopolitan genus. Comparative analyses of 15 plastomes, representing 14 species of subfamily Scutellarioideae, indicate that plastomes within Scutellarioideae contain about 151,000 nucleotides, and possess a typical quadripartite structure. In total, 590 simple sequence repeats, 489 longer repeats, and 16 hyper-variable regions were identified from the 15 plastomes. Phylogenetic relationships among the 14 species representing four of the five genera of Scutellarioideae were resolved with high support values, but the current infrageneric classification of Scutellaria was not supported in all analyses. Complete plastome sequences provide better resolution at an interspecific level than using few to several plastid markers in phylogenetic reconstruction. The data presented here will serve as a foundation to facilitate DNA barcoding, species identification, and systematic research within Scutellaria, which is an important medicinal plant resource worldwide.

The species Phlomoides betonicoides is used medicinally and mainly distributed in southwest China. The first complete plastid genome sequence of P. betonicoides reported here was 151,777 bp long, with the large single copy (LSC) region of 83,205 bp, the small single copy (SSC) region of 17,370 bp and two inverted repeats (IRa and IRb) of 25,601 bp. The plastome contained 114 genes, including 80 protein-coding genes, four ribosomal RNA genes, and 30 transfer RNA genes. The overall GC content was 38.5%. Result from phylogenetic analysis suggests that tribe Phlomideae (Phlomoides) is closely related to tribe Lamieae and tribe Leonureae in present study.

The complete cp genome of Salvia przewalskii was 152,678 bp in length, including a large single copy region (LSC) of 84,102 bp, a small single copy region (SSC) of 17,638 bp and a pair of inverted repeats (IRs) of 25,469 bp. The genome contained 131 genes, including 86 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. The overall GC content of this genome was 38.0%, with the corresponding values of LSC, SSC, and IR regions being 36.2, 31.9, and 43.2%, respectively. Further, the phylogenomic analysis of Mentheae strongly supported the sister relationship of Salvia przewalskii and Salvia miltiorrhiza.

Scutellaria wuana, a new species discovered from a xeric valley in Muli County of Sichuan Province in southwest China, is described and illustrated. Morphologically, the new species shares similarities with S. mairei, but can be readily distinguished by a suite of morphological characters including a white-pubescent erect stem, conspicuous leaf petioles, and a yellow corolla with a trapeziform lower-middle lip lobe. The habitat and distribution of S. wuana are also distinctive. The position of the new species within Scutellaria is examined in a phylogenetic context using the nuclear ribosomal internal and external transcribed spacers. Additionally, we examine leaf epidermal and pollen grain micromorphology of the new species and putative relatives.

Despite considerable progress, many details regarding the evolution of the Arcto-Tertiary flora, including the timing, direction, and relative importance of migration routes in the evolution of woody and herbaceous taxa of the Northern Hemisphere, remain poorly understood. Meehania (Lamiaceae) comprises seven species and five subspecies of annual or perennial herbs, and is one of the few Lamiaceae genera known to have an exclusively disjunct distribution between eastern Asia and eastern North America. We analyzed the phylogeny and biogeographical history of Meehania to explore how the Arcto-Tertiary biogeographic hypothesis and two possible migration routes explain the disjunct distribution of Northern Hemisphere herbaceous plants. Parsimony and Bayesian inference were used for phylogenetic analyses based on five plastid sequences (rbcL, rps16, rpl32-trnH, psbA-trnH, and trnL-F) and two nuclear (ITS and ETS) gene regions. Divergence times and biogeographic inferences were performed using Bayesian methods as implemented in BEAST and S-DIVA, respectively. Analyses including 11 of the 12 known Meehania taxa revealed incongruence between the chloroplast and nuclear trees, particularly in the positions of Glechoma and Meehania cordata, possibly indicating allopolyploidy with chloroplast capture in the late Miocene. Based on nrDNA, Meehania is monophyletic, and the North American species M. cordata is sister to a clade containing the eastern Asian species. The divergence time between the North American M. cordata and the eastern Asian species occurred about 9.81 Mya according to the Bayesian relaxed clock methods applied to the combined nuclear data. Biogeographic analyses suggest a primary role of the Arcto-Tertiary flora in the study taxa distribution, with a northeast Asian origin of Meehania. Our results suggest an Arcto-Tertiary origin of Meehania, with its present distribution most probably being a result of vicariance and southward migrations of populations during climatic oscillations in the middle Miocene with subsequent migration into eastern North America via the Bering land bridge in the late Miocene.