Using scanning electron microscopy and molecular data to discover a new species from old herbarium collections: The case of Phlomoideshenryi (Lamiaceae, Lamioideae).

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.

New species of Asclepias (Apocynaceae), Baphia (Leguminosae), Cochlospermum (Bixaceae) and Endostemon (Lamiaceae) from the Kalahari sands of Angola and NW Zambia, with one new combination in Vangueria (Rubiaceae).

Four new species are described from central and eastern Angola and adjacent NW Zambia. All occur in Kalahari sand savannas rich in endemic and more widely distributed geoxylic suffrutices. Despite being known from very few collections, the conservation status of one of these new species is assessed as Least Concern, as these grasslands are nutrient-poor, are in remote sparsely populated areas, and are not threatened with conversion to agriculture. The remaining three are treated as Data Deficient. In addition, one new combination is provided for Ancylanthosrubiginosus Desf. under Vangueria as V.rubiginosa (Desf.) Lantz is an illegitimate later homonym. We also make orthographic corrections to specific epithets commemorating Ilse von Nolde, a collector who made important collections from Quela in Malange in the 1930s.

Plastome sequences fail to resolve shallow level relationships within the rapidly radiated genus Isodon (Lamiaceae).

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.

Differences in diterpenoid diversity reveal new evidence for separating the genus Coleus from Plectranthus.

Covering: up to 2019The large and medicinally important tropical plant genus Plectranthus (Lamiaceae) was recently split into three separate genera on the basis of molecular and morphological evidence; Plectranthus sensu stricto, Coleus and Equilabium. We found striking differences between the diterpenoids which strongly support this taxonomic split. Coleus is characterised by abietanes oxygenated at C-14 such as royleanones, spirocoleons and acylhydroquinones, which could be useful chemotaxonomic markers to distinguish this genus from Plectranthus s.s. In contrast, the abietanes in Plectranthus s.s. lack C-14 oxygenation, but are often acylated with unusual acids. Equilabium species do not seem to produce diterpenoids. The structures of the nearly 240 abietanes so far reported from Coleus and Plectranthus and their distribution are presented. The aim of this Highlight is to provide an overview of the differences in diterpenoid diversity between these newly defined genera, which are relevant to predict which previously understudied species could hold untapped potential for their medicinal and other economic uses, and to underpin future research on how these plants have evolved to synthesise distinct abietane types.

Hanceola suffruticosa (Lamiaceae, Nepetoideae), a new species from the Sino-Vietnamese border.

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.

Nomenclatural changes in Coleus and Plectranthus (Lamiaceae): a tale of more than two genera.

A synopsis of the genera Coleus Lour, Equilabium A.J.Paton, Mwany. & Culham and Plectranthus L'Hér. (Lamiaceae, Tribe Ocimeae, Subtribe Plecranthinae) is presented. Generic delimitation follows a recently published molecular phylogeny which identified Coleus as the sister of the remaining genera of Subtribe Plectranthinae; Plectranthus as sister to Tetradenia Benth. and Thorncroftia N.E.Br., and a separate phylogenetically distinct genus Equilabium comprising species previously placed in Plectranthus. In this treatment, 294 species of Coleus, 42 of Equilabium, and 72 of Plectranthus are recognized. All but one of the combinations in Equilabium are new as only the genus and type species have been previously published. Two-hundred and twelve names are changed to combinations in Coleus from Plectranthus, Pycnostachys Hook. and Anisochilus Benth.

Phylogeny and historical biogeography of Isodon (Lamiaceae): rapid radiation in south-west China and Miocene overland dispersal into Africa.

Rapid organismal radiations occurring on the Qinghai-Tibetan Plateau (QTP) and the mechanisms underlying Asia-Africa intercontinental disjunctions have both attracted much attention from evolutionary biologists. Here we use the genus Isodon (Lamiaceae), a primarily East Asian lineage with disjunct species in central and southern Africa, as a case study to shed light upon these processes. The molecular phylogeny and biogeographic history of Isodon were reconstructed using sequences of three plastid markers, the nuclear ribosomal internal transcribed spacer (nrITS), and a low-copy nuclear gene (LEAFY intron II). The evolution of chromosome numbers in this genus was also investigated using probabilistic models. Our results support a monophyletic Isodon that includes the two disjunct African species, both of which likely formed through allopolyploidy. An overland migration from Asia to Africa through Arabia during the early Miocene is proposed as the most likely explanation for the present disjunct distribution of Isodon. The opening of the Red Sea in the middle Miocene may appear to have had a major role in disrupting floristic exchange between Asia and Africa. In addition, a rapid radiation of Isodon was suggested to occur in the late Miocene. It corresponds with one of the major uplifts of the QTP and subsequent aridification events. Our results support the hypothesis that geological and climatic events play important roles in driving biological diversification of organisms distributed in the QTP area.

Plectranthus: a review of ethnobotanical uses.

Plectranthus is a large and widespread genus with a diversity of ethnobotanical uses. The genus is plagued with numerous nomenclatural disharmonies that make it difficult to collate accurate data on the uses. The aim of this review is to gather together all ethnobotanical information on Plectranthus and to map the data onto the most up-to-date phylogenetic classification in order to see if there are similar uses among related species and hence provide a framework for the prediction and exploration of new uses of species. The uses of 62 species of Plectranthus were mapped onto a current phylogeny based on DNA sequence data. The phylogeny reveals two major Clades, 1 and 2. The members of Clade 1 (corresponding to the formally recognized genus Coleus) were richer in number and diversity of uses than members of Clade 2 (comprising the remaining species of Plectranthus). The high incidence of synonymy can lead to problems in uncovering a species' ethnobotanical profile. About 30% of all citations of Plectranthus use a synonym and most of the synonyms are attributed to 10 of the most used species, 9 of which are in Clade 1. Members of the 'Coleus' Clade are the most studied group both taxonomically and economically. The higher incidence of study may be as a result of the higher diversity of uses and the fact that species in Clade 1, such as Plectranthus barbatus, Plectranthus amboinicus and Plectranthus mollis, are geographically more widespread than those in Clade 2. Plectranthus species in Clade 1 are frequently used as medicines and are used to treat a range of ailments, particularly digestive, skin, infective and respiratory problems. Plectranthus used as foods, flavours, fodder and materials are also mostly found in Clade 1. Monoterpenoids, sesquiterpenoids, diterpenoids and phenolics have been reported in species of Plectranthus. The abietane diterpenoids are the most diverse of the diterpenoids isolated from species of Plectranthus. The labdane diterpenoid, forskolin, occurs in Plectranthus barbatus and could explain some of the traditional uses of this species. This review highlights the fact that not enough is known about the chemistry of other species of Plectranthus to explain their traditional uses.

Phylogeny and evolution of basils and allies (Ocimeae, Labiatae) based on three plastid DNA regions.

A phylogeny of basils and allies (Lamiaceae, tribe Ocimeae) based on sequences of the trnL intron, trnL-trnF intergene spacer and rps 16 intron of the plastid genome is presented. Several methods were used to reconstruct phylogenies and to assess statistical support for clades: maximum parsimony with equally and successively weighted characters, bootstrap resampling, and Bayesian inference. The phylogeny is used to investigate the distribution of morphological, pericarp anatomy, chemical, and pollen characters as well as the geographical distribution of the clades. Tribe Ocimeae is monophyletic and easily diagnosable with morphological synapomorphies. There are monophyletic clades within Ocimeae that broadly correspond to currently recognised subtribes: Lavandulinae, Hyptidinae, Ociminae, and Plectranthinae. Only Lavandulinae has clear non-molecular synapomorphies. Several currently recognised genera are not monophyletic. Floral morphology consistent with sternotribic pollination is most common in Ocimeae, but there are independent departures from this model. Buzz pollination is likely in some species, the only postulated occurrence of this within Lamiaceae. Quinone diterpenoids and flavones in the leaf exudates differ in their distributions across the phylogeny and this could contribute to differences in the recorded medicinal as well as pesticidal uses of the species in the different clades. Mapping geographic distribution on to an ultrametric phylogenetic tree produced using non-parametric rate smoothing supports an Asiatic origin for Ocimeae. There are several secondary occurrences in Asia arising from the African Ociminae and Plectranthinae clades. Colonisation of Madagascar occurred at least five times, and New World colonisation occurred at least three times.

The chemotaxonomic significance of two bioactive caffeic acid esters, nepetoidins A and B, in the Lamiaceae.

A survey of leaf surface constituents in the family Lamiaceae using HPLC with diode array detection revealed the presence of two characteristic phenolic compounds in many species. The distribution of these phenolics in the Lamiaceae was found to be of taxonomic significance, as they were present in the great majority of species investigated for the subfamily Nepetoideae, including representatives of the well-known genera of culinary herbs, mint, rosemary, sage, thyme and basil. In contrast, they were absent from species of the other subfamilies of Lamiaceae studied and from the related families Verbenaceae, Scrophulariaceae, Acanthaceae and Buddlejaceae. The compounds were isolated from Plectranthus crassus and identified by NMR spectroscopy as the known caffeic acid esters (Z,E)-[2-(3,5-dihydroxyphenyl)ethenyl] 3-(3,4-dihydroxyphenyl)-2-propenoate and (Z,E)-[2-(3,4-dihydroxyphenyl)ethenyl] 3-(3,4-dihydroxyphenyl)-2-propenoate, for which the trivial names nepetoidins A and B are proposed. The presence of this pair of caffeic acid esters adds another character to the chemical, palynological and embryological features distinguishing the Nepetoideae from the other subfamilies of Lamiaceae and related families, and supports the view that the Nepetoideae are a specialised and monophyletic group within the family. Nepetoidin B was shown to have a greater antioxidant activity than gallic, rosmarinic and caffeic acids, and showed activity as an insect phagostimulant. Both compounds were antifungal.

Chemical profiling of Ocimum americanum using external flavonoids.

A HPLC survey was undertaken of the external flavonoids in 111 herbarium specimens of Ocimum americanum L. (O. canum Sims), which were largely collected from their natural habitats throughout Africa and Asia. The purpose of this study was to establish the flavonoid profiles of this species over the full range of its geographic distribution in order to use these for authentication purposes. Six different external flavonoid chemotypes were found. The major chemotype, present in circa 80% of the specimens of both var. americanum and var. pilosum collected throughout the distribution area of the species, was characterised by very high levels of nevadensin, slightly lower levels of salvigenin and much lower levels of up to 15 other external flavones. Of the remaining five chemotypes, two were found in var. americanum and three in var. pilosum. All specimens belonging to these chemotypes were collected in South or East Africa and represented by only a few specimens. These samples contained much smaller levels of flavones than present in the major chemotype of O. americanum and all lacked nevadensin. Xanthomicrol, a compound absent from the main chemotype, was the dominant flavone in two of the minor chemotypes. The external flavonoid profiles found in the six chemotypes of O. americanum were compared with those of O. x citriodorum (11 herbarium specimens studied) and seven other closely related species of Ocimum. The main nevadensin/salvigenin pattern present in O. americanum was also found in O. x citriodorum, O. basilicum and some specimens of O. minimum, but there were strong quantitative differences in external flavonoids among these taxa. The other chemotypes of O. americanum showed some similarities in their external flavone profiles to those found in the closely related East African species O. fischeri, O. forskolei, O. kenyense and O. kilimandscharicum, which occur in the same geographic areas. This suggests that the uncommon chemotypes of O. americanum may have originated by an exchange of genes with other Ocimum species, e.g. by introgressive hybridisation. Despite some similarities in profiles, chemical differences were also found among the species, so that it should be possible to authenticate a large proportion of leaf samples of O. americanum on the basis of external flavonoid profiles.

Scutellarein 4'-methyl ether glycosides as taxonomic markers in Teucridium and Tripora (Lamiaceae, Ajugoideae).

The flavonoid profiles of two monotypic genera, Teucridium and Tripora, have been studied by analytical methods. These genera were formerly placed in the Verbenaceae, but are now classified in the Lamiaceae, subfamily Ajugoideae. The major flavonoids of both genera were identified as glycosides of scutellarein 4'-methyl ether (5,6,7-trihydroxy-4'methoxyflavone) and acacetin (5,7-dihydroxy-4'-methoxyflavone). The new flavone glycoside, scutellarein 4'-methyl ether 7-O-rutinoside, was isolated from Teucridium parvifolium and the rare scutellarein 4'-methyl ether 7-O-glucuronide from Tripora divaricata. The latter compound has only been reported previously in the related genus Clerodendron. The potential of these flavonoids as taxonomic markers for the tribe Ajugoideae is discussed.