Arundinelleae is a taxonomically challenging tribe within Poaceae consisting of two genera. In this study, we examine micro-morphological features of lemmas and pollen for 35 taxa from Arundinelleae. Scanning electron microscopy was employed to assess the taxonomic significance of these morphological characters. The structural details of long and short cells, stomata, micro-hairs, macro-hairs, the distribution of prickles on the lemmas, and characteristics of pollen grains are described and illustrated, and their taxonomic significance is evaluated. The presence or absence of epicuticular waxes and prickle distribution are key characters for classification within Arundinelleae. Within Arundinella, some species can be reliably distinguished by the shape of long-cell walls and the distribution range of prickles on the lemma. While in Garnotia, variation in lemma long-cell wall morphology serves as an important diagnostic feature. Pollen morphological characteristics (including grain size, annulus, operculum, exine ornamentation, and aperture diameter) show some variation among Arundinelleae. Although these latter features provide limited taxonomic utility for delimiting tribes and genera, they enrich the Poaceae palynological dataset.

Documenting species, particularly those that are threatened or endangered, is fundamental to biodiversity conservation. However, many taxa remain scientifically unrecognized, being either undiscovered or unpublished. While some plants can be easily recognized as new species, other identifications are obscured by morphological, taxonomic, and nomenclatural complexity. Detecting cryptic or “hidden” species is therefore essential to understanding biodiversity and plant evolution. Our revisionary studies on Salvia demonstrate that the morphologically complex Salvia caespitosa is not a single species but instead comprises at least four distinct species, three with narrow distributions. This conclusion is supported by integrative evidence from extensive field studies, herbarium and nomenclatural work, laboratory analyses (e.g., morphological measurements and micromorphological studies), and molecular phylogenetic data. Our results indicate that S. caespitosa sensu stricto occurs on calcareous substrates in southern and southeastern Central Anatolia and the eastern Mediterranean, particularly along the Anatolian Diagonal. The newly described species are the geographically restricted S. antalyensis on limestone cliffs near Antalya, S. sivasensis of the gypsum-rich steppe around Sivas and Malatya, and S. karaeri from chalky steppe soils of the Ermenek-Karaman region. Diagnostic traits distinguishing these species include stem length, inflorescence height relative to leaf level, basal leaf morphology, terminal leaflet shape and size, leaf indumentum, and corolla and calyx characters. Lectotypification is provided for S. caespitosa and its synonym, S. pectinifolia. In addition, critical taxonomic evaluations are given for S. pachystachya and its synonym S. sintenisii, as these species are most similar to S. caespitosa. We also provide revised descriptions, an identification key, distributional data, ecological notes, and IUCN Red List assessments for S. caespitosa and the three new species. With the addition of these three species, the Turkish flora now comprises 110 species (including three hybrids) and 118 Salvia taxa, of which 66 are endemic.​​

Hypericum (Hypericaceae) is a large genus of flowering plants that contains approximately 500 species. In China, Hypericum is comprised of 13 sections, 76 species, and 9 subspecies, with at least 30 species that are used in traditional Chinese medicine. Despite its medicinal importance, only a few studies have focused on the molecular phylogenetic relationships of Hypericum within China. In this study, a total of 102 individuals representing 12 sections, 54 species, and 6 subspecies of Hypericum were sampled for phylogenetic analyses, using plastomes and nuclear ribosomal DNA datasets. These analyses constitute the first comprehensive molecular phylogenetic study of Hypericum from China. Phylogenetic analyses indicate that Hypericum is monophyletic and support the treatment of Triadenum and Lianthus as synonyms of Hypericum. Compared with traditionally defined sections based on morphological characteristics, only H. sect. Elodea, H. sect. Hirtella, H. sect. Monanthema, and H. sect. Trigynobrathys are monophyletic. Based on molecular and morphological evidence, we clarify the systematic position of H. elatoides, which is placed in H. sect. Roscyna. In addition, we observe that plastome data provide better resolution for infrageneric relationships within Hypericum than nrDNA sequences, and that the two datasets exhibit substantial cyto-nuclear discordance. This discordance is likely a result of both hybridization and suboptimal phylogenetic signal in the datasets used.

PREMISE:We examined the African arid corridor (AAC) disjunction pattern of vascular plants between northeastern and southwestern Africa in the context of geological and climatic events since the late Miocene. We developed a phylogenetic and biogeographical framework for the arid-adapted genus Sesamothamnus (Pedaliaceae), a classic example of the AAC disjunction pattern. METHODS:A phylogenetic tree based on next-generation sequencing of 512 nuclear genes and entire plastomes for all species of Sesamothamnus was time calibrated. Parsimony analyses were employed for morphological data. We gleaned the literature for examples of the AAC disjunction that were time calibrated or could be dated and compared them to climatic and geological changes from the Miocene to Pleistocene. Habit, dispersal mechanism, arid-adapted features, and geographic source area were collected. RESULTS:The nuclear and plastome data provide congruent phylogenies for Sesamothamnus, indicating that the species restricted to northeastern Africa are sister to the southwestern species and diverged about 8.4 million years ago (Ma). Time calibrated splits for the AAC disjunct pattern were obtained for 73 vascular plant clades with dates ranging from 34 Ma to the Pleistocene, with the majority dated to the late Miocene, Pliocene, and Pleistocene. CONCLUSIONS:Most clades exhibiting the AAC disjunction pattern, including Sesamothamnus, appear associated with several waves of aridification affecting both northeastern, eastern, and southwestern Africa involving the rise of C4 and CAM photosynthesis, succulence, spiny vegetation, and bovid herbivory. The AAC disjunction pattern is complex, appears to involve migration, rather than simple vicariance, and exhibits a strong southwest to northeast migration bias.

Ajuga (Lamiaceae, Ajugoideae) consists of ca. 69 species, most of which are herbaceous perennials. The genus is widely distributed across Eurasia, with extensions into Africa and Australasia. Although medicinally important, the phylogenetic relationships within Ajuga remain poorly understood. In this study, we present the first global phylogenetic analysis of the genus, based on 697 DNA sequences generated from seven chloroplast markers (matK, ndhF, psbA-trnH, rbcL, rpl32-trnL, rps16 intron, trnL-trnF region) and two nuclear regions (nrITS, nrETS). Sampling represented 51 species, accounting for all previously recognized infrageneric taxonomic categories. Although some topological incongruences were observed between the nuclear and plastid phylogenies, analyses using both maximum likelihood and Bayesian inference methods strongly support the monophyly of Ajuga and reveal two highly supported major clades. This split is further supported by geographical distribution and several morphological characteristics, including the shape of the upper corolla lip, the number of flowers per verticillaster, and corolla color. Additionally, none of the previously proposed infrageneric classifications are supported, indicating the need for a comprehensive taxonomic revision of the genus.

Rhodomyrtus tomentosa (Ait.) Hassk. is useful for its ornamental, medicinal, and ecological characteristics, and is considered a “Neglected and Underutilized Crop Species”. However, our understanding of the geographic structure and evolutionary history of its wild populations is limited. To address this gap, we investigated genomic data from 284 samples of R. tomentosa from 28 wild populations in southern China. The genetic diversity of populations in different regions revealed the similar trends using whole-genome and RAD-seq data, and Hainan Island having a higher genetic diversity than other regions. The 28 populations clustered into three distinct groups: (a) GROUP1 on the eastern mainland within Guangdong, Fujian, and Hunan Provinces; (b) GROUP2 on the western mainland within Guangxi and Yunnan Provinces; and (c) GROUP3 on Hainan Island. Mantel tests and redundancy analyses revealed population differentiation was affected by distance and environmental factors such as annual average radiation. Demographic history and gene flow analyses indicated the mainland populations and the Hainan Island populations diverged around 0.93 MYA, with gene flow primarily occurring from Hainan Island and the coastal regions (such as Zhanjiang in Guangdong and Fangchenggang in Guangxi) towards the mainland, reflecting an expansion trend within the species. PSMC’ analyses indicated that the populations of the three groups underwent a bottleneck during the Pleistocene due to glacial-interglacial cycles and geological events. Niche analysis revealed that the ice ages caused habitat contraction for the species, and populations with higher genetic diversity are generally distributed in areas with more suitable habitats. This study elucidates the current genetic distribution of the species within China and suggests that drastic Pleistocene climate change and geographical events caused population divergence and fluctuations in effective population size, shaping the current genetic distribution of R. tomentosa. These findings provide a theoretical basis for the genetic conservation and improvement of R. tomentosa.

Southwest China is characterized by high plateaus, large mountain systems, and deeply incised dry valleys formed by major rivers and their tributaries. Despite the considerable attention given to alpine plant radiations in this region, the timing and mode of diversification of the numerous dry valley plant lineages remain unknown. To address this knowledge gap, we investigated the macroevolution of Isodon (Lamiaceae), a lineage commonly distributed in the dry valleys in southwest China and wetter areas of Asia and Africa. We reconstructed a robust phylogeny encompassing nearly 90% of the approximately 140 extant Isodon species using transcriptome and genome-resequencing data. Our results suggest a rapid radiation of Isodon during the Pliocene that coincided with a habit shift from herbs to shrubs and a habitat shift from humid areas to dry valleys. The shrubby growth form likely acted as a preadaptation allowing for the movement of Isodon species into these dry valleys. Ecological analyses highlight drought-related factors as key drivers influencing the niche preferences of different growth forms and species richness of Isodon. The interplay between topography and the development of the East Asian monsoon since the middle Miocene likely contributed to the formation of the dry valley biome in southwest China. This study enhances our understanding of evolutionary dynamics and ecological drivers shaping the distinctive flora of southwest China and reveals the strategies employed by montane plants in response to climate change and dryland expansion, thus facilitating conservation efforts globally.

Accurate species delimitation is often challenging in cases of recent rapid radiations, where morphological similarities can lead to an underestimation of species diversity. By not recognizing taxonomic diversity, taxa that are economically or ecologically valuable may be overlooked. Salvia honania and S. meiliensis are morphologically quite similar and geographically restricted to the Dabie Mountains in central China. They provide an ideal system for exploring speciation and diversification within S. sect. Drymosphace, a group with noteworthy medicinal value. Previous molecular phylogenetic studies have provided insufficient evidence to clarify the taxonomic boundaries between these two taxa. Here, we employ an integrative taxonomic approach, combining population genetics, phylogeography, and morphology, to define the taxonomic status of the two species. A total of 211 individuals from 16 populations were analyzed across their entire geographical distributions. Significant genetic differentiation was observed, with clear interspecific divergence in genetic diversity, genetic structure, and population dynamics. Phylogenetic analyses and haplotype networks revealed distinct clades for each taxon, and significant phylogeographic structure highlighted the role of geographic factors in fostering genetic differentiation. Morphologically, the presence of hairs inside the calyx tube (S. honania) and on the anther surface (S. meiliensis) were found to be reliable diagnostic characters for species identification. We conclude that S. honania and S. meiliensis are independently evolving lineages, likely in the early stages of speciation. This study illustrates recent and ongoing speciation in two herbaceous plants with narrow distributions and morphological similarities. It underscores the importance of integrative taxonomy for accurate species delimitation within genetically divergent but morphologically similar lineages.

Despite tremendous progress towards clarifying phylogenetic relationships within the mint family (Lamiaceae), uncertainty remains regarding relationships among some major clades as well as the proper placement of some genera. While researching the genus Nepeta, a species from northeastern Morocco, N. nepetoides, attracted our attention due to its distinct morphology relative to other species of Nepeta. To explore the systematic position of N. nepetoides, Bayesian and maximum likelihood analyses were conducted using chloroplast, nuclear ribosomal, and low-copy nuclear markers. For phylogenetic analyses, a total of 5 accessions and 49 samples were newly sequenced for this publication, with the remainder coming from previous studies. Results from all three gene regions suggest that N. nepetoides should not be treated within Nepeta, but instead recognized as a distinct genus, the resurrected Pitardia. In addition, Pitardia is not even in the same subtribe as Nepeta (Nepetinae), and instead should be considered as a member of the subtribe Menthinae, a group that includes most of the culinary spices (e.g., oregano, peppermint, thyme) from the mint family. Notably, all analyses point to Pitardia being sister to the rest of subtribe Menthinae. Furthermore, lectotypes are designated for P. nepetoides and P. caerulescens, the taxonomic status of Pitardia is reassessed, and an updated and extended morphological description of Pitardia is provided based on herbarium specimens and field observations.

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. 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

Background and Aims The California Floristic Province (CA-FP) is the most species-rich region of North America north of Mexico. One of several proposed hypotheses explaining the exceptional diversity of the region is that the CA-FP harbours myriad recently diverged lineages with nascent reproductive barriers. Salvia subgenus Audibertia is a conspicuous element of the CA-FP, with multiple sympatric and compatible species.Methods Using 305 nuclear loci and both organellar genomes, we reconstruct species trees, examine genomic discordance, conduct divergence-time estimation, and analyse contemporaneous patterns of gene flow and mechanical reproductive isolation.Key Results Despite strong genomic discordance, an underlying bifurcating tree is supported. Organellar genomes capture additional introgression events not detected in the nuclear genome. Most interfertility is found within clades, indicating that reproductive barriers arise with increasing genetic divergence. Species are generally not mechanically isolated, suggesting that it is unlikely to be the primary factor leading to reproductive isolation.Conclusions Rapid, recent speciation with some interspecific gene flow in conjunction with the onset of a Mediterranean-like climate is the underlying cause of extant diversity in Salvia subgenus Audibertia. Speciation has largely not been facilitated by gene flow. Its signal in the nuclear genome seems to mostly be erased by backcrossing, but organellar genomes each capture different instances of historical gene flow, probably characteristic of many CA-FP lineages. Mechanical reproductive isolation appears to be only part of a mosaic of factors limiting gene flow.

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 classifi-cation 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 syn-onyms.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.

We have previously suggested that a shift from bee to hummingbird pollination, in concert with floral architecture modifications, occurred at the crown of Salvia subgenus Calosphace in North America ca. 20 mya (Kriebel et al. 2020 and references therein). Sazatornil et al. (2022), using a hidden states model, challenged these assertions, arguing that bees were the ancestral pollinator of subg. Calosphace and claiming that hummingbirds could not have been the ancestral pollinator of subg. Calosphace because hummingbirds were not contemporaneous with crown subg. Calosphace in North America. Here, using a variety of models, we demonstrate that most analyses support hummingbirds as ancestral pollinators of subg. Calosphace and show that Sazatornil et al. (2022) erroneously concluded that hummingbirds were absent from North America ca. 20 mya. We contend that "biological realism" - based on timing and placement of hummingbirds in Mexico ca. 20 mya and the correlative evolution of hummingbird associated floral traits - must be considered when comparing models based on fit and complexity, including hidden states models.

Distributed in Central Asia, Metastachydium (Lamiaceae) is a poorly understood and rare monotypic genus, with few collections known. The systematic position of this enigmatic genus within Lamiaceae has remained unresolved due to its poor representation in herbaria and coincident lack of available materials for molecular phylogenetic analysis. Facilitated by some recent collections, we performed Bayesian inference and maximum likelihood analyses, using an 80-protein-coding plastid-gene dataset of Lamioideae, to infer the systematic placement of Metastachydium at the tribal level within Lamioideae. In addition, we used an 8-plastid-DNA-region dataset as well as the nuclear ribosomal internal transcribed spacer to determine the phylogenetic affinities of Metastachydium. All phylogenetic analyses agree that Metastachydium is a member of Phlomideae and deeply nested within the genus Phlomoides, suggesting the need to expand the latter to include Metastachydium. Hence, a new combination, Phlomoides sagittata comb. nov., is proposed, and we present the first available photographs and an amended morphological description of P. sagittata. In addition, the infrageneric circumscription of Phlomoides is not supported, as most sections and subsections are not monophyletic. Hybridization and incomplete lineage sorting, following rapid diversification within Phlomoides, seem to be the source of incongruence between the nuclear and plastid tree topologies.

Hybridization among plants is fairly common, particularly in instances where closely related species are sympatric. One example of a group in which hybridization has been detected is the genus Salvia (Lamiaceae; mint family). Salvia is a diverse genus consisting of about 1,000 species and is defined primarily by having only two stamens, each with their anther sacs separated by elongated connective tissue. The genus has diversity centers around the world, including Southwest Asia and the Mediterranean region, Mexico/ Central America, northern and central South America, and temperate East Asia. The genus also has a smaller species radiation of 19 species in western North America, subgenus Audibertia centered in California, and there has been documented evidence of hybridization within the subgenus. For this study we investigated potential hybridization among Salvia columbariae and Salvia greatae, two species with a sympatric distribution in the Orocopia Mountains region of Southern California. These species are placed in different sections of subgenus Audibertia, and hybridization has not yet been documented between sections of this subgenus. To examine relationships between the species, we compared molecular phylogenies from nuclear ribosomal DNA and chloroplast DNA. The resulting phylogenies did not show evidence of hybridization between these species. Although no evidence of hybridization was found, it is possible that additional sampling could yield different results.

The seed morphology of 40 taxa within the genus Hypericum (Hypericaceae) from China, representing 9 sections of the genus, was examined using both Light and Scanning Electron Microscopy to evaluate the taxonomic relevance of macro- and micro-morphological features. Details articulating variation in seed size, color, shape, appendages, and seed coat ornamentation are described, illustrated, and compared, and their taxonomic importance is discussed. Seeds were generally brown in color and cylindric-ellipsoid to prolonged cylindric in shape. Seed size displayed wide variation, ranging from 0.37-1.91 mm in length and 0.12-0.75 mm in width. Seed appendages were observed as a characteristic morphological feature. Seed surface ornamentation has high phenotypic plasticity, and four types (reticulate, foveolate, papillose, and ribbed) can be recognized. In general, seed color and shape have limited taxonomic significance. However, some other features represent informative characters that can be used efficiently in distinguishing the studied taxa at the section and/or species levels. The findings illustrate that considerable taxonomic knowledge can be obtained by investigating the seed features of Hypericum, and the use of Scanning Electron Microscopy can reveal inconspicuous morphological affinities among species and play a role in taxonomic and systematic studies of the genus Hypericum.

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.

Salvia (Lamiaceae) is a sub-cosmopolitan genus of about 1000 species that often employ a "staminal lever mechanism" that is thought to have spurred species diversification within the genus. The function and evolution of ventral outgrowths or connective teeth, associated with the lever mechanism in some species of Salvia, is often unclear despite the wealth of pollination observations across the genus and the major role that pollinators play in driving diversification within the genus. We document the role of these teeth in pollination studies of bee-pollinated Salvia farinacea, examine connective teeth across other bee- and hummingbird-pollinated species of New World subg. Calosphace, and provide an evolutionary scenario for the connective teeth in context of the staminal lever. Our observations show that the larger teeth function as pressure points at the floral entrance and, when pressed by a pollinator, facilitate movement of the lever. Multiple shifts in pollinator within subg. Calosphace may have resulted in further modifications of the connective and possible further losses and independent origins of connective teeth in Calosphace. Other distantly related subgenera (e.g., Sclarea, Glutinaria) display morphologically and spatially different protuberances on the connective, suggesting that connective teeth only evolved near the base of subg. Calosphace.

Biogeographic disjunctions, including intercontinental disjunctions, are frequent across plant lineages and have been of considerable interest to biologists for centuries. Their study has been reinvigorated by molecular dating and associated comparative methods. One of the "classic" disjunction patterns is that between Eastern Asia and North America. It has been speculated that this pattern is the result of vicariance following the sundering of a widespread Acrto-Teritary flora. Subtribe Nepetinae in the mint family (Lamiaceae) is noteworthy because it contains three genera with this disjunction pattern: Agastache, Dracocephalum, and Meehania. These disjunctions are ostensibly the result of three separate events, allowing for concurrent testing of the tempo, origin, and type of each biogeographic event. Using four plastid and four nuclear markers, we estimated divergence times and analyzed the historical biogeography of Nepetinae, including comprehensive sampling of all major clades for the first time. We recover a well-supported and largely congruent phylogeny of Nepetinae between genomic compartments, although several cases of cyto-nuclear discordance are evident. We demonstrate that the three disjunctions are pseudo-congruent, with unidirectional movement from East Asia at slightly staggered times during the late Miocene and early Pliocene. With the possible exception of Meehania, we find that vicariance is likely the underlying driver of these disjunctions. The biogeographic history of Meehania in North America may be best explained by long-distance dispersal, but a more complete picture awaits deeper sampling of the nuclear genome and more advanced biogeographical models.