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Liparis casseabria, a new species of Orchidaceae, is described and illustrated from Natma Taung National Part, Chin State, Myanmar. It is morphologically similar to L. jovispluvii, but can be easily distinguished from the latter by having conspicuous underground tuber, narrowly lanceolate petals, dramatically folded lip with entire margin and emarginated apex.

Ceropegia jilongensis, a new species from Jilong, Xizang, China, is described and illustrated. This species is similar to C. hookeri, but clearly differs in its indumentum of pedicel and corolla tube, ovoid cage size, corolla lobes and interstaminal corona lobes shape. It is also similar to C. salicifolia and C. angustifolia, but easily distinguished by its leaf shape, peduncle length, indumentum of pedicel and corolla tube, interstaminal corona lobes shape. A comparison table of related species is provided.

Colocasia kachinensis S.S. Zhou & J.T. Yin, is described and illustrated as a new species of Araceae from Kachin, Mynamar. The morphological characters are compared to those of other Colocasia species. Colocasia kachinensis is closely related to C. menglaensis J.T Yin, H. Li & Z.F. Xu, 2004, but differs from in having an erect stem, no stolons, smaller size, a different pattern of surface bristle distribution and male flowers 1–4-androus with stamens connate in truncate synandrium.

A new species, Ophiorrhiza monsvictoriae S.S.Zhou & L.D.Duan, discovered at Natma Taung (Mt.Victoria) National Park, Chin State, Myanmar, is described and illustrated. The new species is morphologically similar to O. dulongensis, but differs from the latter by its stipules broadly triangular, 2–4 mm long, inflorescence axillary, 1-flowered, bracts lanceolate to subulate, 1–2 mm long, puberulous, calyx pilose, 1–2 mm long, lobes and tube equal length, corolla narrowly funnelform, 15 mm long, puberulous outside.

Myanmar is known for its high species richness of genus Gastrochilus; however, most of them lack proper information for taxonomic revision. During four years of field investigation in Myanmar, two new distributional records were encountered, namely, G. arunachalensis and G. corymbosus and one species, i.e. G. pechei was rediscovered after its original description. The three species were not easy to interpret from the available original descriptions and types due to severely shrunk or poorly preserved specimens. Therefore, we hereby present more detailed illustrations and updated descriptions for these species, based on freshly collected materials.

Two taxa of Amomum (Zingiberaceae), Amomum erythranthum and Amomum ampliflorum, from Putao, Kachin State of Northern Myanmar are described and illustrated as new to science. Amomum erythranthum is morphologically similar to A. subulatum and A. nimkeyense in having similar yellow flowers, but can be distinguished by its reddish floral tube, red anther connective, red and pubescent fruit. Amomum ampliflorum is similar to A. maximum, A. dealbatum and A. odontocarpum in white flower, but differs in its longer inflorescence and much larger flower. Two species, Amomum pauciflorum and Wurfbainia microcarpum are recorded for the flora of Myanmar for the first time. Data on ecology, phenology, distribution, conservation status, similarities to the related taxa, as well as colour photographs and line drawings of the type, and voucher specimens are provided for all reported taxa.

Climate refugia are locations where plants are able to survive periods of regionally adverse climate. Such refugia may affect evolutionary processes and the maintenance of biodiversity. Numerous refugia have been identified in the context of Quaternary climate oscillations. With climate warming, there is an increasing need to apply insights from the past to characterize potential future refugia. Mountainous regions, due to the provision of spatially heterogeneous habitats, may contain high biodiversity, particularly important during climate oscillations. Here, we highlight the importance of mountaintops as climate refugia, using the example of high-mountain oaks which are distributed on the ranges of the Himalaya–Hengduan Mountains, and at high elevations in tropical rainforests. The occurrences of cold-adapted high-mountain oaks on mountaintops amidst tropical rainforest indicate that such locations are and will be climate refugia as global warming continues. We examine factors that predict the occurrence of future climate refugia on mountaintops using recognized historical refugia. Future research is needed to elucidate the fine-scale processes and particular geographic locations that buffer species against the rapidly changing climate to guide biodiversity conservation efforts under global warming scenarios.

The complexity of global biodiversity in the tropical Indochina Peninsula and subtropical China bioregions has fascinated biologists for decades, but little is known about the spatiotemporal patterns in these regions. Accordingly, the aims of present study were to investigate the evolutionary and distribution patterns of Engelhardia in these regions and establish a model for examining biogeographic patterns and geological events throughout the tropical Indochina Peninsula and subtropical China. The effects of geological events occurring in the area between the Indochina Peninsula and subtropical China bioregions on the two trees species (i.e., E. roxburghiana and E. fenzelii) were evaluated. A robust phylogenetic framework of 884 individuals from 79 populations was used to generate time-calibrated cytoplasmic and nuclear phylogenetic frameworks based on cpDNA, nrDNA, and nSSR data, respectively. When considered along with ancestral area reconstructions, the genetic data were also used to assess and reconstruct the species' population genetic structure and diversity. These analyses yielded important information about the (1) historical distribution relationships between the tropical and subtropical flora of China; (2) effects of the East Asian summer monsoon (EASM) on the evolutionary history of Asia's plants; and (3) importance of biogeography in conservation planning. Although cytoplasmic-nuclear discordance indicated cpDNA and nrDNA were subject to distinct evolutionary mechanisms that reflected respective evolutionary histories of the plastid and nuclear genomes of prior demographic and biogeographic events. The tropical elements of Engelhardia occupied the Indochina Peninsula during the early Eocene, whereas the subtropical elements were transformed from the tropical elements during Miocene cooling and the onset of the EASM at the Oligocene-Miocene boundary, intensified during the late Miocene and Pliocene, facilitating the transformation of Engelhardia from the tropical Indochina Peninsula to subtropical China. Demographic history provided insights into prominent planning frameworks in conservation biology, namely that subtropical China functioned as a refugium during past climate oscillations and will continue to serve in this capacity in the future.

Biodiversity managements are always hot topics in China that harbors so much hyper-biodiversity. However, biodiversity loss is continuing as economic growth is accelerating during recent decades. Questions that need to be addressed with regard to the conflict between biodiversity conservation and economic growth are: how much conservation effort is required and what measures are necessary to reconcile conflicts. Here we evaluate the phenomenon and conservation status of representative of the rare plants with important economic values in tropical China. They are facing the danger of extinction, even are disappearing as they are discovered. This topic enables us to propose conservation measures to resolve the dilemma that continued biodiversity loss is linked closely with economic growth. A combination of ex situ conservation, in situ conservation and in-depth surveys, is necessary to protect biodiversity in the tropical China. Insights gained from current conflict will permit a greater understanding of the rare plants with significant evolutionary and ecological roles but which are threatened by economic development, thus enabling the relevant departments to develop and implement appropriate conservation policies.

Background Dai, Hani, and Yao people, in the trans-boundary region between China, Laos, and Vietnam, have gathered plentiful traditional knowledge about wild edible plants during their long history of understanding and using natural resources. The ecologically rich environment and the multi-ethnic integration provide a valuable foundation and driving force for high biodiversity and cultural diversity in this region. However, little study has uncovered this unique and attractive culture to the world. Methods We conducted ethnobotanical survey in 20 villages of Jiangcheng County from 2016 to 2020. Altogether 109 local Dai, Hani, and Yao people were interviewed, and their traditional knowledge about wild edible plants was recorded. Voucher specimens were identified by the authors and deposited in the herbarium of Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences (HITBC). The use value was used as a quantitative index to evaluate the consumption frequency and relative importance of the wild edible plants. The Jaccard index was calculated to assess the usage similarity of different areas. The relationship of age and recognized wild edible plants by different ethnic people was performed by R. Results A total of 211 wild edible plants, belonging to 71 families and 151 genera, were recorded. These plants were consumed as wild edible vegetables, seasonal fruits, salads, spices, sour condiments, tonic soups, tea substitutes, liquor brewing, or dyeing materials. The use value (UV), current cultivation, market availability, and the quantitative traditional knowledge inheritance situation of these wild edible plants among different generations, were analyzed. Based on the data from the threatened species list of China’s higher plants and the IUCN Red List, the food plant list for Asia Elephant, the Subject Database of China Plant, and the calculated UV score, the top 30 most important wild edible plants were selected for further cultivation in some local villages. Conclusion Traditional knowledge of wild edible plants, owned by Dai, Hani, and Yao people in Jiangcheng County, is rich but at risk of being lost among the young generation. Diversified cultivation of wild edible plants by the local communities could be a solution for the sustainable use of natural resources and to conserve the endangered species in this trans-boundary region.

Zingiber natmataungense S.S.Zhou & R.Li (Zingiberaceae), a new species from Natma Taung National Park, Chin State, Myanmar, is described and illustrated. The new species is morphologically similar to Z. yunnanense, but differs by: leaf blade abaxially light green, glabrous, ligule sparsely pubescent, ca. 2–3 mm, bracts glabrous; calyx white 20–21 × 3.2–3.5 mm, glabrous, apex obviously 3-toothed; corolla tube white, ca. 3.9–4.1 cm, labellum lateral lobes, ca. 1.5–1.7 × 0.6–0.7 cm; stamen with sparse pubescent, filament white, glabrous,1–2 mm; anther connective appendage yellowish proximally, purplish distally; ovary white, sparsely white pubescent, epigynous glands, ca. 6–7 mm long, tapered, apex whorled, yellow. This new species is also similar to Z. teres, but has a different flower colour.

Enhanced efficacy in species delimitation is critically important in biology given the pending biodiversity crisis under global warming and anthropogenic activity. In particular, delineation of traditional classifications in view of the complexity of species requires an integrative approach to effectively define species boundaries, and this is a major focus of systematic biology. Here, we explored species delimitation of Engelhardia in tropical and subtropical Asia. In total, 716 individuals in 71 populations were genotyped using five chloroplast regions, one nuclear DNA region (nrITS), and 11 nuclear simple sequence repeats (nSSR). Phylogenetic trees were constructed and relationships among species were assessed. Molecular analyses were then combined with 14 morphological characteristics of 720 specimens to further explore the species boundaries of Engelhardia. Integrating phylogenetic and morphological clusters provided well-resolved relationships to delineate seven species. The results suggested that: first, that E. fenzelii, E. roxburghiana, E. hainanensis, E. apoensis, and E. serrata are distinct species; second, E. spicata var. spicata, E. spicata var. aceriflora, E. spicata var. colebrookeana, and E. rigida should be combined under E. spicata and treated as a species complex; third, E. serrata var. cambodica should be raised to species level and named E. villosa. We illuminated that bias thresholds determining the cluster number for delimiting species boundaries were substantially reduced when morphological data were incorporated. Our results urge caution when using the concepts of subspecies and varieties in order to prevent confusion, particularly with respect to species delimitation for tropical and subtropical species. In some cases, re-ranking or combining subspecies and/or varieties may enable more accurate species delimitation.

Dendrobium naungmungense, a new species from Naungmung, Kachin State, North Myanmar, is described and illustrated. It is morphologically similar to D. ciliatilabellum and D. vexabile, but the epichile is oblong with three long-ciliate laminae and the column wing has significant denticulation. A preliminary risk-of-extinction assessment shows that the new species should be regarded as Critically Endangered (CR) according to the IUCN Red List Categories and Criteria.

Hedychium putaoense Y.H. Tan & H.B. Ding, a new species of Zingiberaceae from Putao, Kachin state, Northern Myanmar, is described and illustrated. It is similar to H. densiflorum Wall. and H. longipedunculatum A.R.K. Sastry & D.M. Verma, but differs by its very small bract (4–6 × 2.5–3 mm vs. 18–19 × 5–5.5 mm and ca. 11 × 7 mm, respectively), semicircle and dark red bracteole, orange flower and broadly falcate to lanceolate lateral staminodes.

Aristolochia sinoburmanica Y.H.Tan & B.Yang, a new species of Aristolochiaceae from Putao, Kachin State, Myanmar, is described and illustrated. According to morphology (strongly curved perianth, 3-lobed limb, as well as 3-lobed gynostemium, anthers 6, adnate in 3 pairs to the base of gynostemium, opposite to the lobes), the species belongs to Aristolochia subgenus Siphisia. It is morphologically similar to A. faviogonzalezii, A. hainanensis, A. tonkinensis, A. saccata and A. xuanlienensis. The major differences between them are outlined and discussed. A detailed description, along with line drawings, photographs, habitat, distribution and conservation status, as well as a comparison to morphologically similar species, are also provided.

Coelogyne magnifica (Orchidaceae), a new species from Putao, Kachin State, Myanmar, is described and illustrated. It belongs to Coelogyne section Ocellatae Pfitzer & Kraenzl. and it is morphologically similar to Coelogyne corymbosa and C. taronensis, but can be distinguished from these species by its larger flowers, lanceolate sepals and petals, a narrowly ovate lip, which has two bright yellow patches surrounded by shiny brownish red and two fimbriate or erose-lacerate lateral keels on the lip. The major differences between these species are outlined and discussed.

Trivalvaria rubra and Trivalvaria casseabriae, two new species of Annonaceae from Putao, Kachin State, Myanmar, are here described and illustrated. They are morphologically similar to T. costata and T. macrophylla. The major differences between them are outlined and discussed. A diagnostic key to the species of Trivalvaria is provided.

Coelogynevictoria-reginae, a new species of sectionProliferae, from Natma Taung (Mt.Victoria) National Park, Chin State, Myanmar, is described and illustrated. It is morphologically similar toC.prolifera, but the clustered pseudobulbs, pure brownish- red flowers and column wing with irregular notches at the apex of the new species differ from the other species. A preliminary risk-of-extinction assessment shows that the new species is regarded as EN C2a[i] according to the IUCN Red List Categories and Criteria.

Trivalvaria rubra and Trivalvaria casseabriae, two new species of Annonaceae from Putao, Kachin State, Myanmar, are here described and illustrated. They are morphologically similar to T. costata and T. macrophylla. The major differences between them are outlined and discussed. A diagnostic key to the species of Trivalvaria is provided.

Canthium longipetalum Y.H. Tan & S.S. Zhou, a new species of Rubiaceae from Putao, Kachin State, Myanmar, is described and illustrated. It is morphologically similar to C. neilgherrense which has ca. 3 mm long pedicels and corolla lobes, but differs from it by having 2.5–3.2 cm long pedicels and 1.2–1.4 cm long corolla lobes.

A new species of Ericaceae, Agapetes reflexiloba, from Putao, Kachin State, Myanmar, is described and a colour plate is provided, affiliated to Agapetes sect. Agapetes ser. Graciles Airy-Shaw. The new species is morphologically similar to A. nutans, A. linearifolia and A. angustifolia of the Series Graciles in having linear to lanceolate narrow leaves and corymbose-racemose inflorescences and very short filaments. It is, however, readily distinguished from its three relatives by having a purplish red to dark red acuminate corolla apex in flower buds and conspicuously reflexed corolla lobes in anthesis, and corolla light brownish yellow to brownish yellow, and with 5 deep purple red zig-zag stripes. The rediscovery of Agapetes bhareliana and A. linearifolia is also reported from Kachin state, Northern Myanmar, after a gap of more than eight decades. Both are new records for Myanmar. Agapetes nana was also recollected 64 years after the collection made by F. Kingdon Ward between 1952 and 1953. Agapetes nana (Griff.) Hook. f. var. robusta Airy Shaw is newly proposed as a synonym of A. nana. A revised taxonomic description along with colour plate and distributional map are provided.

Magnoliaceae include about 350 species that are widely distributed in tropical, subtropical and warm-temperate regions of Asia and the Americas, from near sea level to 3400 m elevation (Vázquez-García et al. 2016). Numerous phylogenetic studies of Magnoliaceae in the last two decades (Law 1984, Figlar & Nooteboom 2004, Xia et al. 2008, Sima & Lu. 2012, Kim & Suh 2013, Romanov & Dilcher 2013), have ultimately led to almost universal acceptance of the classification of Figar & Nooteboom (2004), consisting of only two genera: Liriodendron Linneaus (1753: 535) with only two species, and a broad concept of Magnolia Linneaus (1753: 535) including all other species. Myanmar currently has only 21 species of Magnolia (Govaerts et al. 2017).

Agapetes brevipedicellata, a new species of Ericaceae from Putao, Kachin State, Myanmar, is here described and illustrated. It is morphologically similar to Agapetes pseudogriffithii, but can be easily distinguished from the latter by its nearly fleshy branchlets, linear-lanceolate leaf blades, stout, fleshy, bracteate peduncles, pedicels and calyx pale greenish tinged with pale pink, and stems and branches with prominent leaf and inflorescence scars.

Two new species of the genus Impatiens (Balsaminaceae) from Putao, Kachin State, Myanmar, are here described and illustrated. Impatiens casseabriae can be easily recognized by its narrowly elliptic to narrowly oblanceolate leaves, petioles up to 3 mm long, lower lateral united petals 25–40 mm long. Impatiens putaoensis differs from its closely related species I. xanthina in having light greenish yellow flowers, lateral sepals ovate to elliptic, lower lobe of united petals semilunar, upper lobe of united petals dolabrate, dorsal petal ovate to nearly orbicular, with a narrow inconspicuous dorsal crest. Molecular phylogenetic analyses of sequences from both nuclear ribosomal and plastidgenes confirm that the two new species are distinct from previously recorded species.

Reinwardtia Dumortier (1822: 19) (Linaceae) with one species Reinwardtia indica Dumortier (1822: 19) is mainly distributed in northern India, China and Southeast Asia (Dressler et al. 2014). The genus belongs to subfamily Linoideae, tribe Eulineae (Winkler 1931, Dressler et al. 2014). Reinwardtia indica is heterostylous, and dimorphic pollen and stigmas are reported (Bahadur et al. 1996, Sugawara et al. 2002). Historically, two Reinwardtia species, R. tetragyna Planchon (1848: 523) and R. trigyna (Roxburgh, 1799:357) Planchon (1848: 522) have been recorded in Myanmar (Kress et al. 2003), but R. trigyna has been treated as a synonym of R. indica (Grierson & Long 1987, The Plant List 2013, Dressler et al. 2014).

Spatial dispersion patterns of trees at different life stages are an important aspect to investigate in understanding the mechanisms that facilitate species co-existence. In this paper, Ripley’s univariate L(r) and bivariate L 12(r) functions were used to analyze spatial distribution patterns and spatial associations across different life stages of 131 tree species in a 20-ha plot of a tropical rainforest in Xishuangbanna, southwest China. Our results show that: (1) Saplings of 109 (83.2%) species have a significant clumped distribution, which confirms the ubiquity of clumped spatial distributions among tropical tree species. (2) Adults of 126 (96.2%) species have a random distribution suggesting that density-dependent mortality can make the spatial pattern of tropical trees more regular with time. (3) At small scales (0–10 m), 95 (72.5%) species have a neutral or negative sapling-adult association, implying that there is recruitment limitation within the vicinity of their conspecific adults. The reduction in spatial clumping in going from younger to older life stages and the neutral or negative sapling-adult association imply density-dependent mortality in the vicinity of adult trees. In accordance with the Janzen–Connell hypothesis, such density-dependent mortality can free up space for other species to colonize, contributing to the maintenance of species diversity.

The orchid flora of Myanmar is highly diverse but as yet poorly known in the continental Asia, which is largely a result of periods of past instability and political isolation of the country. Also the remoteness of many orchid-rich areas and the difficulties of investigation in rugged terrain have also played a role (Ormerod & Kumar, 2003; Kurzweil & Lwin, 2014). According to recent estimates about 800 orchid species are distributed in Myanmar (Kurzweil & Lwin, 2014), which were probably underestimated. Many new distribution records and new species have been published in the last few years (Ormerod, 2002, 2006, 2012; Ormerod & Kumar, 2003, 2008; Ormerod & Wood, 2010; Nyunt, 2006; Kurzweil et al., 2010; Kurzweil & Lwin, 2012a,b; Tanaka et al. 2011).

Acranthera burmanica, a new species of Rubiaceae from Kachin, Myanmar, is here described and illustrated. It is morphologically similar to A. sinensis, but can be easily distinguished from the latter by its stem and branches densely strigose throughout; ovate leaves; calyx distinctly shorter than corolla tube, lobes lanceolate, apex attenuate; stipules triangular, apex acute not cuspidate; lower part of filaments connate into a tube.