New Guinea has the world's richest island flora.

New Guinea is the world's largest tropical island and has fascinated naturalists for centuries1,2. Home to some of the best-preserved ecosystems on the planet3 and to intact ecological gradients-from mangroves to tropical alpine grasslands-that are unmatched in the Asia-Pacific region4,5, it is a globally recognized centre of biological and cultural diversity6,7. So far, however, there has been no attempt to critically catalogue the entire vascular plant diversity of New Guinea. Here we present the first, to our knowledge, expert-verified checklist of the vascular plants of mainland New Guinea and surrounding islands. Our publicly available checklist includes 13,634 species (68% endemic), 1,742 genera and 264 families-suggesting that New Guinea is the most floristically diverse island in the world. Expert knowledge is essential for building checklists in the digital era: reliance on online taxonomic resources alone would have inflated species counts by 22%. Species discovery shows no sign of levelling off, and we discuss steps to accelerate botanical research in the 'Last Unknown'8.

Molecular and morphological evidence supports the resurrection of Chrysospleniumguangxiense H.G.Ye & Gui C.Zhang (Saxifragaceae).

Chrysospleniumguangxiense H.G.Ye & Gui C.Zhang was first described as a new species in 1994 but later synonymized in the Flora of China treatment with C.glossophyllum H.Hara. Plastid genomes and nrDNA sequences were used to infer the phylogenetic relationships of selected taxa in Chrysosplenium. Our phylogenetic analyses revealed that C.guangxiense belongs to sect. Alternifolia, is closely related to Chrysospleniumhydrocotylifolium H.Lév. & Vaniot but distant from C.glossophyllum. Morphologically, C.guangxiense could be easily distinguished from C.glossophyllum by having robust rhizomes, basal leaves with a long cuneate base and fewer teeth in the margin, curled sepal margins, and red, larger seeds. It could also be easily distinguished from C.hydrocotylifolium by possessing long elliptic leaves and a long cuneate leaf base. Along with the phylogenetic studies, the complete plastid genome of C.guangxiense was also reported. The plastid genome was 154,004 bp in length and comprised two inverted repeats (IRs) of 28,120 bp, separated by a large single-copy of 80,646 bp and a small single-copy of 17,118 bp. A total of 111 functional genes were discovered, comprising 78 protein-coding genes, 29 tRNA genes, and four rRNA genes. Based on assessment of morphological and molecular data Chrysospleniumguangxiense H.G.Ye & Gui C.Zhang is resurrected from C.glossophyllum H.Hara at species level. A global conservation assessment classifies C.guangxiense as Vulnerable (VU).

Phylogenetic position and plastid genome structure of Vietorchis, a mycoheterotrophic genus of Orchidaceae (subtribe Orchidinae) endemic to Vietnam.

The orchid genus Vietorchis comprises three species, all discovered in the 21 century. Each of these species is achlorophyllous, mycoheterotrophic and is known to be endemic to Vietnam. The type species of the genus, V. aurea, occurs in a single location in northern Vietnam within a lowland limestone karstic area. Vietorchis furcata and V. proboscidea, in contrast, are confined to mountains of southern Vietnam, far away from any limestone formations. Taxonomic placement of Vietorchis remained uncertain for the reason of inconclusive morphological affinities. At the same time, the genus has never been included into molecular phylogenetic studies. We investigate the phylogenetic relationships of two species of Vietorchis (V. aurea and V. furcata) based on three DNA datasets: (1) a dataset comprising two nuclear regions, (2) a dataset comprising two plastid regions, and (3) a dataset employing data on the entire plastid genomes. Our phylogenetic reconstructions support the placement of Vietorchis into the subtribe Orchidinae (tribe Orchideae, subfamily Orchidoideae). This leads to a conclusion that the previously highlighted similarities in the rhizome morphology between Vietorchis and certain mycoheterotrophic genera of the subfamilies Epidendroideae and Vanilloideae are examples of a convergence. Vietorchis is deeply nested within Orchidinae, and therefore the subtribe Vietorchidinae is to be treated as a synonym of Orchidinae. In the obtained phylogenetic reconstructions, Vietorchis is sister to the photosynthetic genus Sirindhornia. Sirindhornia is restricted to limestone mountains, which allows to speculate that association with limestone karst is plesiomorphic for Vietorchis. Flower morphology is concordant with the molecular data in placing Vietorchis into Orchidinae and strongly supports the assignment of the genus to one of the two major clades within this subtribe. Within this clade, however, Vietorchis shows no close structural similarity with any of its genera; in particular, the proximity between Vietorchis and Sirindhornia has never been proposed. Finally, we assembled the plastid genome of V. furcata, which is 65969 bp long and contains 45 unique genes, being one of the most reduced plastomes in the subfamily Orchidoideae. The plastome of Vietorchis lacks any rearrangements in comparison with the closest studied autotrophic species, and possesses substantially contracted inverted repeats. No signs of positive selection acting on the protein-coding plastid sequences were detected.

An integrative approach to species delimitation sinks three Chinese limestone karst Elatostema (Urticaceae) species.

Elatostema is recognized as a taxonomically difficult group due to the reduced nature of the tiny flowers and inflorescences, also the large number of species (ca 650 to 700). Different opinions on morphological species delimitation have resulted in instability, which is problematic in such a speciose group. In this paper, the taxonomic status of three putative species, E.robustipes, E.scaposum, E.conduplicatum and their hypothetical closest relatives, was revised using morphological and molecular observations. Morphological comparison suggested high similarity between E.robustipes & E.retrohirtum, E.scaposum & E.oblongifolium, E.conduplicatum & E.coriaceifolium, respectively. Phylogenetic analyses of four universal DNA barcodes (ITS, trnH-psbA, matK and rbcL) suggested that each species pair represents a single evolutionary lineage. Taking these two findings together, we propose E.robustipes to be a synonym of E.retrohirtum, E.scaposum a synonym of E.oblongifolium, and E.conduplicatum a synonym of E.coriaceifolium. Our results recover the number, shape and size of the bracts and bracteoles to be relatively stable characters, and the disposition of the male inflorescences on modified stems to be an unstable character, unsuitable for species delimitation in Elatostema.

Three new species of Elatostema (Urticaceae) from Thailand.

Three new species of Elatostema (Urticaceae) from Thailand, E.kaweesakii Triyutth. & L.F.Fu, sp. nov., E.rubricaule Triyutth. & L.F.Fu, sp. nov. and E.saxatile Triyutth. & L.F.Fu, sp. nov., are newly described and illustrated. These new species can be distinguished by the presence of rhizome. Elatostemakaweesakii is similar to E.atroviride. Elatostemakaweesakii is a lithophyte growing in limestone crevices. It differs from E.atroviride by its large swollen rhizome, glabrous stem, glabrous receptacle, number of tepal in staminate flower, absence of tepal in pistillate flower, presence of staminodes in pistillate flower and smooth achene. Elatostemarubricaule and E.saxatile are found on sandstone habitats. They have distinct flattened and disk-like rhizome. Elatostemarubricaule is distinguished by its distinct sulcate and reddish stem with flattened and disc-like rhizome and chartaceous leaves with entire margin. Elatostemasaxatile resembles E.bulbiferum but differs by its flattened and disc-like rhizome, acute leaf apex, glabrous receptacle in pistillate inflorescences, presence of staminodes in pistillate flower, and its sandstone habitat. Descriptions, distribution, ecological and phenological data are provided.

Microchiritaminor (Gesneriaceae), a new species from north-western Vietnam.

Microchiritaminor (Gesneriaceae), a new species from the limestone area in Son La Province, north-western Vietnam, is described here. The new species resembles M.hamosa, but it differs by the combination of corolla tube shape, stamens number and the length of pistil. Detailed morphological description, together with photographic plates, information on phenology, distribution, ecology and preliminary conservation status of the new species are presented.

Pileadanxiaensis (Urticaceae), a new species in the Danxia landform from Guangdong, China including a description of the entire chloroplast genome.

Pileadanxiaensis L.F.Fu, A.K.Monro & Y.G.Wei, a new species of Urticaceae from Danxia landform, Guangdong, China, is described and photographed. Phylogenetic analyses based on three DNA regions (ITS, trnL-F and rbcL) suggest that the new species belongs to P.sect.Pilea. Within the section, the new species is morphologically most similar to P.sinocrassifolia and P.peploides. Plastid genome and ribosomal DNA (rDNA) sequences of the new species are assembled and annotated. The plastid genome is 151,857 bp in length and comprises two inverted repeats (IRs) of 25,307 bp separated by a large single-copy of 82,836 bp and a small single-copy of 18,407 bp. A total of 113 functional genes are recovered, comprising 79 protein-coding genes, 30 tRNA genes, and four rRNA genes. A global conservation assessment suggests that P.danxiaensis should be classified as of Least Concern (LC).

Actinostephanus (Gesneriaceae), a new genus and species from Guangdong, South China.

Actinostephanus, a new genus from southern China, is described and colorfully illustrated with a single species, A.enpingensis. This new genus is morphologically most similar to Boeica and Leptoboea, nevertheless, it can be easily distinguished from the latter two by the following characteristics, such as leaves in whorls of three, all closely clustered at the top; corolla bowl-shaped, 5-lobed, actinomorphic; capsule hard, oblong-ovoid, short, 3-4 mm long, densely appressed villous, wrapped by persistent densely pubescent calyx lobes, style persistent. The new genus and related genera were sequenced using the next-generation sequencing technique. The whole plastid genome of the new genus is 154, 315 - 154, 344 bp in length. We reconstructed phylogenetic trees using the dataset of 80 encoded protein genes of the whole plastid genome from 47 accessions based on ML and BI analyses. The result revealed that the new genus was recovering in a polytomy including Boeica, Rhynchotechum, and Leptoboea with strong support, congruent to the morphological evidence. A global conservation assessment was also performed and classifies A.enpingensis as Least Concern (LC). In addition, after a review of recently described species of Gesneriaceae, we propose that plant enthusiasts, especially Gesneriad fans, have been playing an increasingly important role in the process of new taxa-discoveries.

Complete chloroplast genome sequence of Procris crenata C.B.Rob (Urticaceae).

The complete chloroplast (cp) genome of Procris crenata C.B.Rob was reported. The cp genome was 154,124 bp in length and contained two inverted repeats (IRs) of 25,626 bp, which were separated by large single-copy and small single-copy of 84,599 bp and 18,273 bp, respectively. The GC content was 36.5%. A total of 113 functional genes were encoded, comprising 79 protein-coding genes, 30 tRNA genes, and four rRNA genes. This is the first reported plastid genome in Procris (Urticaceae), which will be useful data for resolving the relationship within the family.

Leaf epidermal micromorphology in Aspidistra (Asparagaceae): diversity and taxonomic significance.

Micromorphological characters of leaf epidermis were investigated in 69 species of Aspidistra using scanning electron microscopy. Sculpture of epidermis varies from smooth to verrucose and rugose in the genus. The abaxial epidermis of some species bears papillae, whereas the adaxial surface uniformly lacks the papillae. Sculpture type of epidermis and density of papillae are generally found to be stable characters at a species level. The infraspecific variation of epidermis sculpture, where present, ranges from smooth to verrucose or from verrucose to rugose. Micromorphological characters of leaf epidermis are shown to have potential taxonomic significance in Aspidistra; in combination with the type of shoot structure, they allow to subdivide the species into 13 groups. The groups are largely incongruent with floral morphological traits. An identification key to the studied species of Aspidistra based on vegetative characters (gross leaf and shoot morphology and characters of leaf epidermis) is presented.

Primulina papillosa (Gesneriaceae), a new species from limestone areas of Guangxi, China.

Primulina papillosa Z.B. Xin, W.C. Chou & F. Wen, a new species from limestone areas of Guangxi, China, is described and illustrated here. It morphologically resembles P. linearifolia (W.T. Wang) Yin Z. Wang and P. pseudolinearifolia W.B. Xu & K.F. Chung, but can be easily distinguished by some combined characters, especially its leaf blades densely papillose-hispid. We found only one population at the type locality with no more than 200 individuals, so that this new species is provisionally assessed as Critically Endangered (CR) using IUCN Criteria.

Chrysosplenium sangzhiense (Saxifragaceae), a new species from Hunan, China.

Chrysosplenium sangzhiense Hong Liu, a new species from Hunan, China, is described and illustrated. The phylogenetic analysis revealed that the new species belongs to subgen. Chrysosplenium and is closely related to C. grayanum, C. nepalense and C. sinicum. The chromosome number of the new species is 2n = 46, indicating a novel basic number x = 23 in Chrysosplenium that is different from other species. This also suggests that C. sangzhiense is probably an allopolyploid derivative of a species with x = 11 and one with x = 12. Morphologically, C. sangzhiense can be easily distinguished from C. grayanum, C. nepalense, C. sinicum and C. cavaleriei, a species not included in our phylogenetic analysis by a suite of characters relating to the sterile shoots, basal leaves, cauline leaves, flowering stem, sepals, disc, capsule and seed. A global conservation assessment is performed, and classifies C. sangzhiense as Least Concern (LC).

Chayamaritia vietnamensis (Gesneriaceae), a new species from Son La Province, northern Vietnam.

Chayamaritia vietnamensis, a new species from Son La Province, northern Vietnam, is described and illustrated. The phylogenetic study revealed that the new species is most closely related to C. banksiae and C. smitinandii. The morphological comparison suggests it as the third new species of Chayamaritia and distinguished from C. banksiae and C. smitinandii by a combination of morphological characters of leaf blades, bracts, calyx and corolla, especially its peltate leaf blades. This species is provisionally assessed as endangered (EN B1ab(iii), B2ab(iii)) using IUCN Categories and Criteria. Information on ecology, phenology and an identification key for the known Chayamaritia species are also provided.

Complete chloroplast genome sequence of Passiflora serrulata Jacq. (Passifloraceae).

This study was the first report for the complete chloroplast genome of Passiflora serrulata Jacq. (Passifloraceae). The cp genome was 149,683 bp in length contained two inverted repeats (IRs) of 25,470 bp, which were separated by large single-copy (LSC) and small single-copy (SSC) of 86,252 bp and 13,491 bp, respectively. A total of 110 functional genes were encoded, comprised 76 protein-coding genes, 30 tRNA genes, and four rRNA genes. The GC content was 37.0%. The maximum likelihood phylogenetic tree indicated that P. serrulata was recovered as the member of subg. Passiflora and most closely related to the clade formed by P. serratodigitata and P. ligularis.

A new species of Chrysosplenium (Saxifragaceae) from Shaanxi, north-western China.

Chrysosplenium zhouzhiense Hong Liu, a new species from Shaanxi, north-western China, is described and photographed. The new species belongs to Subgen. Gamosplenium Sect. Nephrophylloides Ser. Macrophylla and is most similar to C. macrophyllum and C. zhangjiajieense from which it differs by having a shorter stem, rhizome absent, basal leaf absent, sterile branch arising from the flowering stem and a light yellow flower with longer stamen. A global conservation assessment is performed and classifies C. zhouzhiense as Endangered (EN).

Primulina hochiensis var. ochroleuca (Gesneriaceae), a new variety from a limestone area of Guangxi, China, and errata on five new species of Primulina.

Primulina hochiensis var. ochroleuca, a new variety from a limestone hill of karst areas, Guangxi, China is described with color photographs. It resembles P. hochiensis var. hochiensis, P. hochiensis var. ovata and P. hochiensis var. rosulata, but can be easily distinguished by a combination of characteristics, especially by its corolla color. We found only one population with approx. 3000 mature individuals at the type locality. This variety is provisionally assessed as vulnerable [VU C1] using IUCN criteria.

Michaelmoelleria (Gesneriaceae), a new lithophilous dwelling genus and species with zigzag corolla tube from southern Vietnam.

Michaelmoelleria, a new genus from southern Vietnam is described with a single species, M. vietnamensis. The new genus is morphologically most similar to Deinostigma and Tribounia but it differs from the latter two by having four fertile stamens. Nuclear ribosomal internal transcribed spacer (ITS) region and plastid trnL-F intron spacer (trnL-F) DNA sequence data from the new genus and eighty-seven species representing 42 genera within tribe Didymocarpeae are used to resolve its generic placement. The molecular evidence reveals that it is most closely related to Cathayanthe rather than Deinostigma and Tribounia. The chromosome number is counted as 2n = 36 that further clarified its distinction comparing to the related genera within tribe Didymocarpeae. A global conservation assessment is also performed and classifies Michaelmoelleria vietnamensis as Critically Endangered (CR).

A new variety of Didymocarpus (Gesneriaceae) from Guangdong, China.

A new variety of Didymocarpus, D.heucherifoliusvar.gamosepalus from Guangdong, China, is described and illustrated with photographs. It closely resembles the more widespread D.heucherifolius within a number of morphological characters. However, it can be easily distinguished from the latter according to the new taxon: calyx base connate, 5-lobed from middle to above middle, larger flowers (up to 5 cm long) and glabrous corolla.

The complete chloroplast genome of Aster hypoleucus (Asteraceae: Astereae): an endemic species from China.

This study was the first report about complete chloroplast genome of Aster hypoleucus (Asteraceae, Astereae), an endemic species in Xizang (China). The circular whole cp genome of A. hypoleucus was 152,300 bp in length, contained a large single-copy (LSC) region of 84,031 bp and a small single-copy (SSC) region of 18,269 bp. These two regions were separated by a pair of inverted repeat regions (IRa and IRb), each of them 25,000 bp in length. A total of 134 functional genes were encoded, consisted of 89 protein-coding genes, 37 tRNA genes, and eight rRNA genes. The overall GC content of the chloroplast genome sequence was 37.3%, and the GC contents of the LSC, SSC, and IR regions were 35.2%, 31.2%, and 43.0%, respectively.

Complete chloroplast genome sequence of Petrocodon jingxiensis (Gesneriaceae).

The complete chloroplast genome of Petrocodon jingxiensis (Yan Liu, H.S. Gao, and W.B. Xu) A. Weber and Mich. Möller was determined in this study. The cp genome was 153,056 bp in length including two inverted repeats (IRs) of 25,405 bp, which were separated by LSC and SSC of 84,154 bp and 18,092 bp, respectively. The GC content was 41.9%. The genome encoded 112 functional genes, including 79 protein-coding genes, 29 tRNA genes, and four rRNA genes. This plastid genome is the first report for the Petrocodon in Gesneriaceae which will be useful data for developing markers for further studies on resolving the relationship within the genus.