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Abstract Cinnamomum chago is a tree species endemic to Yunnan province, China, with potential economic value, phylogenetic importance, and conservation priority. We assembled the genome of C. chago using multiple sequencing technologies, resulting in a high-quality, chromosomal-level genome with annotation information. The assembled genome size is approximately 1.06 Gb, with a contig N50 length of 92.10 Mb. About 99.92% of the assembled sequences could be anchored to 12 pseudo-chromosomes, with only one gap, and 63.73% of the assembled genome consists of repeat sequences. In total, 30,497 genes were recognized according to annotation, including 28,681 protein-coding genes. This high-quality chromosome-level assembly and annotation of C. chago will assist us in the conservation and utilization of this valuable resource, while also providing crucial data for studying the evolutionary relationships within the Cinnamomum genus, offering opportunities for further research and exploration of its diverse applications.

Abstract Background Michelia lacei W.W.Smith (Magnoliaceae), was classified as a Plant Species with Extremely Small Populations (PSESP) by the Yunnan Provincial Government in both action plans of 2012 and 2021. This evergreen tree is known for its high ornamental and scientific value, but it faces significant threats due to its extremely small population size and narrow geographical distribution. The study aims to understand the genetic structure, diversity, and demographic history of this species to inform its conservation strategies. Results The analysis of transcriptome data from 64 individuals across seven populations of M. lacei identified three distinct genetic clusters and generated 104,616 single-nucleotide polymorphisms (SNPs). The KM ex-situ population, originating from Longling County, exhibited unique genetic features, suggesting limited gene flow. The genetic diversity was substantial, with significant differences between populations, particularly between the KM lineage and the OTHER lineage. Demographic history inferred from the data indicated population experienced three significant population declines during glaciations, followed by periods of recovery. We estimated the effective population size (Ne) of the KM and OTHER lineages 1,000 years ago were 85,851 and 416,622, respectively. Gene flow analysis suggested past gene flow between populations, but the KM ex-situ population showed no recent gene flow. A total of 805 outlier SNPs, associated with four environmental factors, suggest potential local adaptation and showcase the species' adaptive potential. Particularly, the BZ displayed 515 adaptive loci, highlighting its strong potential for adaptation within this group. Conclusions The comprehensive genomic analysis of M. lacei provides valuable insights into its genetic background and highlights the urgent need for conservation efforts. The study underscores the importance of ex-situ conservation methods, such as seed collection and vegetative propagation, to safeguard genetic diversity and promote population restoration. The preservation of populations like MC and BZ is crucial for maintaining the species' genetic diversity. In-situ conservation measures, including the establishment of in-situ conservation sites and community engagement, are essential to enhance protection awareness and ensure the long-term survival of this threatened plant species.

Abstract Background Corybas taliensis is an endemic species of sky islands in China. Its habitat is fragile and unstable, and it is likely that the species is threatened. However, it is difficult to determine the conservation priority or unit without knowing the genetic background and the overall distribution of this species. In this study, we used double digest restriction-site associated DNA-sequencing (ddRAD-seq) to investigate the conservation genomics of C. taliensis. At the same time, we modeled the extent of suitable habitat for C. taliensis in present and future (2030 and 2090) habitat using the maximum-entropy (MaxEnt) model. Results The results suggested that the related C. fanjingshanensis belongs to C. taliensis and should not be considered a separate species. All the sampling locations were divided into three genetic groups: the Sichuan & Guizhou population (SG population), the Hengduan Mountains population (HD population) and Himalayan population (HM population), and we found that there was complex gene flow between the sampling locations of HD population. MT was distinct genetically from the other sampling locations due to the unique environment in Motuo. The genetic diversity (π, H e ) of C. taliensis was relatively high, but its contemporary effective population size (N e ) was small. C. taliensis might be currently affected by inbreeding depression, although its large population density may be able to reduce the effect of this. The predicted areas of suitable habitat currently found in higher mountains will not change significantly in the future, and these suitable habitats are predicted to spread to other higher mountains under future climate change. However, suitable habitat in relatively low altitude areas may disappear in the future. This suggests that C. taliensis will be caught in a ‘summit trap’ in low altitude areas, however, in contrast, the high altitude of the Himalaya and the Hengduan Mountains are predicted to act as ‘biological refuges’ for C. taliensis in the future. Conclusions These results not only provide a new understanding of the genetic background and potential resource distribution of C. taliensis, but also lay the foundation for its conservation and management.

The Cypripedium forrestii is an orchid species with extremely small populations (PSESP) in Yunnan, China. C. forrestii is range-restricted and less-studied than many orchid species, and it is exposed to various threats to its survival. We investigated its potential habitats and collected 52 samples from eight locations, as well as two outgroup species for reference. We developed genetic markers (SNPs) for C. forrestii based on transcriptome sequencing (RNA-seq) data, and analyzed the genetic diversity, population structure, gene flow and demographic history of C. forrestii in detail. C. forrestii is a taxonomically independent species to protect. We found that the genetic diversity of C. forrestii was very low (1.7e-4) compared with other endangered species. We identified three genetic clusters, and several populations with distinct genetic backgrounds. Most genetic diversity was found within sampling sites (87.87%) and genetic clusters (91.39%). Gene flow has been greatly limited over the most recent generations, probably due to geographical distance, historical climate change and habitat fragmentation. We also detected a severe bottleneck event brought about by the recent population constraints. These factors, together with its reproductive characteristics, contribute to the population fragmentation and low genetic diversity of C. forrestii. Based on our findings, we suggest an integrative conservation strategy to protect and recover the genetic diversity of C. forrestii and a further comprehensive study of its ecological traits in the future.

Abstract Rhododendron vialii (subgen. Azaleastrum) is an evergreen shrub with high ornamental value. This species has been listed as a plant species with extremely small populations (PSESP) for urgent protection by China’s Yunnan provincial government in 2021, due to anthropogenic habitat fragmentation. However, limited genomic resources hinder scientifically understanding of genetic threats that the species is currently facing. In this study, we assembled a high-quality haplotype-resolved genome of R. vialii based on PacBio HiFi long reads and Hi-C reads. The assembly contains two haploid genomes with sizes 532.73 Mb and 521.98 Mb, with contig N50 length of 35.67 Mb and 34.70 Mb, respectively. About 99.92% of the assembled sequences could be anchored to 26 pseudochromosomes, and 14 gapless assembled chromosomes were included in this assembly. Additionally, 60,926 protein-coding genes were identified, of which 93.82% were functionally annotated. This is the first reported genome of R. vialii, and hopefully it will lay the foundations for further research into the conservation genomics and horticultural domestication of this ornamentally important species.

Societal Impact Statement A practical and efficient model is crucial for applying conservation actions to threatened species. Plant Species with Extremely Small Populations (PSESP) is a new concept raised jointly by government and scientists from China, targeted toward funding the urgent rescue of threatened plants. With the cooperation of decision‐making departments, scientists, local departments, nongovernment organizations, and local people, we present a case of how the tree species Acer yangbiense was studied and finally rescued. The pipeline and experience in this case will promote the development of the PSESP conservation methods. Summary With only five individuals known for years, the Critically Endangered species Acer yangbiense was listed under the conservation category Plant Species with Extremely Small Populations (PSESP), a concept developed 10 years ago in China, aimed at channeling limited resources to conserve the most threatened plant species. Integrated conservation methods and research were applied to A. yangbiense and introduced in two‐time phases upon the discovery of new populations. Being considered one of the most successfully rescued species, A. yangbiense was removed from the second PSESP list issued in 2021 by Yunnan Province, China. The conservation case has become a model, with replicable pipelines, standards, cooperation, and studies to future PSESP conservation actions. Herein, we discuss the significance of work on A. yangbiense for future conservation actions regarding PSESP and other endangered species.

Abstract Nervonic acid (C24:1 Δ15, NA) is a very long-chain monounsaturated fatty acid, a clinically indispensable resource in maintaining the brain and nerve cells development and regeneration. Till now, NA has been found in 38 plant species, among which the garlic-fruit tree (Malania oleifera) has been evaluated to be the best candidate for NA production. Here, we generated a high-quality chromosome-scale assembly of M. oleifera employing PacBio long-read, short-read Illumina as well as Hi-C sequencing data. The genome assembly consisted of 1.5 Gb with a contig N50 of ~4.9 Mb and a scaffold N50 of ~112.6 Mb. ~98.2% of the assembly was anchored into 13 pseudo-chromosomes. It contains ~1123 Mb repeat sequences, and 27,638 protein-coding genes, 568 tRNAs, 230 rRNAs and 352 other non-coding RNAs. Additionally, we documented candidate genes involved in NA biosynthesis including 20 KCSs, 4 KCRs, 1 HCD and 1 ECR, and profiled the expression patterns of these genes in developing seeds. The high-quality assembly of the genome provides insights into the genome evolution of the M. oleifera genome and candidate genes involved in NA biosynthesis in the seeds of this important woody tree.

Pinus squamata is one of the most threatened conifer species in the world. It is endemic to northeastern Yunnan Province, China, and has been prioritized as a Plant Species with Extremely Small Populations (PSESP). The integrated study of soil properties and rhizosphere bacteria can assist conservation to understand the required conditions for the protection and survival of rare and endangered species. However, differences between the rhizospheric bacterial communities found in the soil surrounding P. squamata at different conservation sites remain unclear. In this study, Samples were collected from wild, ex situ, and reintroduced sites. Bacterial communities in different conservation sites of P. squamata rhizosphere soils were compared using Illumina sequencing. The soil physicochemical properties were determined, the relationships between the bacterial communities and soil physicochemical factors were analyzed, and the potential bacterial ecological functions were predicted. The reintroduced site Qiaojia (RQ) had the highest richness and diversity of bacterial community. Actinobacteria, Proteobacteria, and Acidobacteriota were the dominant phyla, and Bradyrhizobium, Mycobacterium, Acidothermus were the most abundant genera. Samples were scattered (R = 0.93, p = 0.001), indicating significant difference between the different conservation sites. The abundance of Mycobacterium differed between sites (0.01 < p ≤ 0.05), and the relative abundances of Bradyrhizobium and Acidothermus differed significantly among different sites (0.001 < p ≤ 0.01). Soil total potassium (TK) and available nitrogen (AN) were the main factors driving bacterial community at the phylum level (0.01 < p ≤ 0.05). This study generated the first insights into the diversity, compositions, and potential functions of bacterial communities associated with the rhizosphere soils of P. squamata in different conservation sites and provides a foundation to assess the effect of conservation based on bacterial diversity and plant growth-promoting rhizobacteria (PGPR) to guide future research into the conservation of P. squamata.

Tulipa L. (Liliaceae) comprises approximately 150 species. Although Central Asia, the main center of its diversity, includes around 66 species, detailed mapping of their distribution is limited and research on their ecoregional and phytogeographical dispersion is insufficient. This study aimed to map and analyze the distribution patterns of Tulipa across the Central Asian ecoregions and phytogeographical regions to identify potential hotspots for effective conservation efforts. The results identified the Gissaro-Alai open woodlands ecoregion, which hosts 41 species of Tulipa, as the leading hotspot ecoregion. The Ferghana Valley phytogeographical district (Afghano-Turkestan province) was found to be the most suitable habitat for 25 species of Tulipa. We also determined that altitude has a strong influence on the diversity of Tulipa and indicating increase of species richness as elevation rises. However, as elevation rises up from ca. 2000 m a.s.l. species richness also decreases slightly. An analysis of the distribution of sections of Tulipa in Central Asia revealed that around 61% of all species dwell in this area and that the sections Kolpakowskianae and Biflores, which have their greatest diversity of species, are specific to this area. The findings provide valuable insights into the distribution of Tulipa and allow for feasible recommendations and suggestions for their conservation.

The genus Acer is widespread throughout the northern temperate zone, and many species within the genus are of ecological and economical importance. Here we report the newly sequenced chloroplast genome of Acer pubipetiolatum var. pingpienense. This chloroplast genome has a total length of 156,730 bp, and contains a pair of inverted repeats (IRs, 26,743 bp), a large single-copy (LSC) region of 71,582 bp and a small single-copy (SSC) region of 18,092 bp. Phylogenetic analysis suggests that A. pubipetiolatum var. pingpienense is closely related to A. laevigatum, and both fall into Section Palmata. The complete A. pubipetiolatum var. pingpienense chloroplast genome will provide an important genetic resource for future research into the conservation and evolution of this genus. Our findings also suggest that further research is necessary to elucidate the phylogenetic relationships between plant species within this genus.

Understanding the adaptation of plant species will help us develop effective breeding programs, guide the collection of germplasm, and improve the success of population restoration projects for threatened species. Genetic features correlate with species adaptation. Acer yangbiense is a critically endangered plant species with extremely small populations (PSESP). However, no information was available on its seed germination and seedling growth in populations with different genetic characteristics. In this study, we investigated seed germination and compared the performance of 566 seedlings in 10 maternal half-sib families cultivated in Kunming Botanical Garden. The results showed that A. yangbiense seeds required an average of 44 days to start germinating, with a 50% germination rate estimated to take about 47–76 days, indicating slow and irregular germination. There is a trade-off between the growth and survival in A. yangbiense seedlings, with fast growth coming at the cost of low survival. Groups that were able to recover from a recent bottleneck consistently had higher relative growth rates. High genetic diversity and low levels of inbreeding are likely to be responsible for their improved survival during drought conditions and rapid growth under optimal environmental conditions. Our results suggest that maternal genetic traits might be used as indicators for conservation and population restoration. These findings provide us with new information that could be applied to support ex situ conservation and reintroduction of threatened species.

Pinus squamata is a rare and endangered tree endemic to northeastern Yunnan Province, China, and it is listed as a Plant Species with Extremely Small Populations (PSESP) in China for requiring urgent conservation. Furthermore, the actions of ex situ conservation and reintroduction based on artificial propagation have been carried out since some 15 years ago. The rhizosphere microbiome plays an important role in soil quality and plant health. However, how the fungal communities of the rhizosphere differ between wild, ex situ, and reintroduced examples of Pinus squamata remains unclear. Illumina sequencing of the internal transcribed spacer 2 (ITS2) region was used to investigate fungal communities in the P. squamata rhizosphere soil. Rhizospheric fungal community composition, structure, diversity, and ecological function in the soil surrounding wild, ex situ, and reintroduced P. squamata individuals were elucidated. The ex situ site Kunming (EK) had the highest fungal community richness and diversity. The samples collected from six different sites were well separated (R = 0.95, p = 0.001), suggesting significant differences between the sites. Soil total potassium (TK), available phosphorus (AP), and pH were the main factors driving fungal community (0.01 < p ≤ 0.05). Prediction of fungal functional guild in the P. squamata rhizosphere demonstrated that the fungi could be classified as ectomycorrhizal, endophyte, and plant pathogenic fungi. Our research will provide a basis to guide the further selection of conservation sites for P. squamata based on fungal diversity and offer guidance on the antagonistic fungi and plant pathogenic fungi that may be of relevance to the conservation of this rare plant.

Detailed information on the spatial distribution of threatened species is important for biodiversity conservation. Climate change may have an impact on the geographical distribution of organisms worldwide. As a result, research on the effects of climate change on spatial patterns of threatened species is therefore necessary. Although China has the greatest diversity of Acer species of any country in the world, nearly a quarter of them are threatened. We performed species distribution modelling with Maxent to explore the spatial patterns of 20 threatened Acer species in China under present climate and land use conditions, as well as their responses to the predicted future climate change. According to our findings, the two most important climatic factors in determining the potential distribution patterns of threatened Acer in China are annual precipitation and isothermality. The predicted high-richness regions in the current conditions are primarily concentrated in Southeast Tibet, West, Northwest and Southeast Yunnan, the junctions of Yunnan and Guizhou. Our findings show that the majority of threatened Acer species are vulnerable to climate change, fifteen species are likely to be subject to dramatic reductions in areas of potentially suitable habitat in 2070, and four species will undergo significant expansion. Our research suggests that more attention must be paid to global change when enacting conservation measures for threatened Acer trees in China. These findings provide us with valuable information and will inform future conservation as well as decision taking regarding threatened Acer species.

Firmiana major (Malvaceae) is a dominant tree species in hot, arid valleys with savanna vegetation in southwest China. Due to severe human disturbance, the populations of F. major declined sharply and was once considered extinct in the wild. Until 2020, eight populations of F. major were found by our investigation and it was listed as a Plant Species of Extremely Small Populations (PSESP) in Yunnan Province, China, for urgent rescuing during the next decade. To guide its conservation, the genetic structure, demographic history, and distribution model were studied. Four genetic groups of F. major were revealed and their divergence times coincided with warming periods during the last glacial stage. The distribution model showed a narrow habitat for F. major around the hot, arid areas of Yuanmou Basin, Jingsha arid-hot valleys and their adjacent areas, which enhanced its endangered situation. Based on the study, several conservation suggestions for F. major were proposed including adopting its germplasms with better drought tolerance for afforestation in this area.

Abstract Background It has been recognized that a certain amount of habitat disturbance is a facilitating factor for the occurrence of natural hybridization, yet to date we are unaware of any studies exploring hybridization and reproductive barriers in those plants preferentially occupying disturbed habitats. Buddleja plants (also called butterfly bush) generally do grow in disturbed habitats, and several species with hybrid origin have been proposed, based solely on morphological evidence. Results In the present study, we test the hypothesis that B. × wardii is of natural hybridization origin in two sympatric populations of three taxa including B. × wardii and its parents (B. alternifolia and B. crispa) plus 4 referenced parental populations, using four nuclear genes and three chloroplast intergenic spacers, as well as with 10 morphological characters. Our results suggest that at both sites B. × wardii is likely to be a hybrid between B. alternifolia and B. crispa, and moreover, we confirm that most of the hybrids examined are F1s. That these plants are F1s is further supported by morphology, as no transgressive characters were detected. B. crispa was found to be the maternal parent in the Bahe (BH) population, from cpDNA evidence. However, in the Taji (TJ) population, the direction of hybridization was difficult to establish due to the shared cpDNA haplotypes between B. alternifolia and B. crispa, however we still predicted a similar unidirectional hybridization pattern due to results from cross-specific pollination treatments which supported the “SI × SC rule”. Conclusions The presence of mainly F1 hybrids can successfully impede gene flow and thus maintain species boundaries in parental species in a typical distribution of Buddleja, i.e. in disturbed habitats.

Elucidating the genetic background of threatened species is fundamental to their management and conservation, and investigating the demographic history of these species is helpful in the determination of the threats facing them. The woody species of the genus Magnolia (Magnoliaceae) have high economic, scientific and ecological values. Although nearly half of all Magnolia species have been evaluated as threatened, to date there has been no population genetic study employing Next Generation Sequencing (NGS) technology in this genus. In the present study, we investigate the conservation genomics of Magnolia fistulosa, a threatened species endemic to the limestone area along the Sino-Vietnamese border, using a double digest restriction-site-associated DNA-sequencing (ddRAD-seq) approach. To increase the reliability of our statistical inferences, we employed two approaches, Stacks and ipyrad, for SNP calling. A total of 15,272 and 18,960, respectively, putatively neutral SNPs were generated by Stacks and ipyrad. Relatively high genetic diversity and large population divergence were detected in M. fistulosa. Although higher absolute values were calculated using the ipyrad data set, the two data sets showed the same trends in genetic diversity (π, He), population differentiation (FST) and inbreeding coefficients (FIS). A change in the effective population size of M. fistulosa within the last 1 Ma was detected, including a population decline about 0.5–0.8 Ma ago, a bottleneck event about 0.2–0.3 Ma ago, population fluctuations during the last glacial stage, and the recovery of effective population size after the last glacial maximum. Our findings not only lay the foundation for the future conservation of this species, but also provide new insights into the evolutionary history of the genus Magnolia in southeastern Yunnan, China.

Abstract Background Amorphophallus albus P. Y. Liu & J. F. Chen (Araceae) is a plant species with extremely small populations (PSESP) and an important economic crop endemic to dry-hot valleys along the Jinsha River. In order to gain information for sustaining the development and conservation of A. albus, we studied the genetic diversity and population structure of this species using microsatellite markers (SSR). In this study, we analysed 364 individuals belonging to 24 populations, including four wild populations and three ex-situ cultivated populations, collected in the provinces Yunnan, Sichuan and Hubei. Results The population genetic analyses indicated that A. albus possesses moderate genetic diversity with the percentage of polymorphic loci (PPL) from 69.23 to 100%, an expected heterozygosity (He) of 0.504 and an average Shannon’s Information Index (I) 0.912. Analysis of molecular variance (AMOVA) indicated that most of the variance (71%) resided within populations and the estimated gene flow (Nm) was 0.61. The results of UPGMA cluster tree, STRUCTURE analyses together with the Mantel test (R2 = 0.352, P

Gene flow between sympatric congeneric plants is thought to be very common and may pose serious threats to endangered species. In the present study, we evaluate the genetic diversity and divergence of three sympatric Rhododendron species in Jiaozi Mountain using newly developed microsatellites through the Illumina MiSeq sequencing approach. Genetic diversity of all three Rhododendron species studied was moderate in comparison to genetic parameters previously reported from species of this genus. Interestingly, genetic structure analysis of the three species identified a possible hybrid origin of the threatened Rh. pubicostatum. This sympatry should be considered a unimodal hybrid zone, since Rh. pubicostatum is predominant here. Unimodal hybrid zones are uncommon in Rhododendron, despite the fact that hybridization frequently occurs in the genus. Issues pertaining to the conservation of Rh. pubicostatum resulting from admixture of genetic material from its parental species are discussed.

Abstract Background Primula is a large genus of flowering herbs well known for their heterostyly. Currently few natural hybrids are known and reproductive barriers in this genus in the wild have received little attention. However, there is instance of hybridization between rare and widely-spread species, and conservation implications of such situation is poorly understood. In the present study, we investigated hybridization patterns and reproductive barriers between a wide spread species, Primula poissonii and a rare species P. anisodora, of which only three populations are currently known. Results Pollinator-mediated reproductive isolation was strong between parental species but not significant between hybrids and parental species. Hand pollination experiments showed significant reduction of both fruit- and seed-set for heterospecific pollination as compared with conspecific pollination for both parental species. Furthermore, hybrids had higher fruit- and seed-set when pollinated with P. anisodora pollen as opposed to P. poissonii pollen. Microsatellites identified backcrosses to P. anisodora in two of the three populations of P. anisodora, and additionally more individuals of P. anisodora showed introgression from P. poissonii than vice versa. Conclusions These results provide evidence for potential genetic swamping of the P. anisodora populations, which could pose a serious threat for this locally endemic species.

Nyssa yunnanensis is a deciduous tree species in the family Nyssaceae within the order Cornales. As only eight individual trees and two populations have been recorded in China’s Yunnan province, this species has been listed among China’s national Class I protection species since 1999 and also among 120 PSESP (Plant Species with Extremely Small Populations) in the Implementation Plan of Rescuing and Conserving China’s Plant Species with Extremely Small Populations (PSESP) (2011-2-15). Here, we present the draft genome assembly of N. yunnanensis. Using 10X Genomics linked-reads sequencing data, we carried out the de novo assembly and annotation analysis. The N. yunnanensis genome assembly is 1475 Mb in length, containing 288,519 scaffolds with a scaffold N50 length of 985.59 kb. Within the assembled genome, 799.51 Mb was identified as repetitive elements, accounting for 54.24% of the sequenced genome, and a total of 39,803 protein-coding genes were predicted. With the genomic characteristics of N. yunnanensis available, our study might facilitate future conservation biology studies to help protect this extremely threatened tree species.

Plant diversity is currently being lost at an unprecedented rate, resulting in an associated decrease in ecosystem services. About a third of the world's vascular plant species face the threat of extinction due to a variety of devastating activities, including, over-harvesting and over exploitation, destructive agricultural and forestry practices, urbanization, environmental pollution, land-use changes, exotic invasive species, global climate change, and more. We therefore need to increase our efforts to develop integrative conservation approaches for plant species conservation. Botanical gardens devote their resources to the study and conservation of plants, as well as making the world's plant species diversity known to the public. These gardens also play a central role in meeting human needs and providing well-being. In this minireview, a framework for the integrated missions of botanical gardens, including scientific research, in/ex situ conservation, plant resource utilization, and citizen science are cataloged. By reviewing the history of the development of Kunming Botanical Garden, we illustrate successful species conservation approaches (among others, projects involving Camellia, Rhododendron, Magnolia, Begonia, Allium, Nepenthes, medicinal plants, ornamental plants, and Plant Species with Extreme Small Populations), as well as citizen science, and scientific research at Kunming Botanical Garden over the past 80 years. We emphasize that Kunming Botanical Garden focuses largely on the ex situ conservation of plants from Southwest China, especially those endangered, endemic, and economically important plant species native to the Yunnan Plateau and the southern Hengduan Mountains. We also discuss the future challenges and responsibilities of botanical gardens in a changing world, including: the negative effects of outbreeding and/or inbreeding depression; promoting awareness, study, and conservation of plant species diversity; accelerating global access to information about plant diversity; increasing capacity building and training activities. We hope this minireview can promote understanding of the role of botanical gardens. Keywords: Botanical gardens, Citizen science, Conservation biology, Endangered plants, Germplasm, Horticulture

Manglietia ventii is a highly endangered plant species endemic to Yunnan province in China, where there are only five known small populations. Despite abundant flowering there is very low fruit and seed set, and very few seedlings in natural populations, indicating problems with reproduction. The causes of low fecundity in M. ventii are not known, largely because of insufficient knowledge of the species pollination ecology and breeding system. We conducted observations and pollination experiments, and analyzed floral scents to understand the pollinator–plant interactions and the role of floral scent in this relationship, as well as the species breeding system. Like the majority of Magnoliaceae, M. ventii has protogynous and nocturnal flowers that emit a strong fragrance over two consecutive evenings. There is a closing period (the pre-staminate stage) during the process of anthesis of a flower, and we characterize the key flowering process as an “open-close-reopen” flowering rhythm with five distinct floral stages observed throughout the floral period of this species: pre-pistillate, pistillate, pre-staminate, staminate, and post-staminate. Flowers are in the pistillate stage during the first night of anthesis and enter the staminate stage the next night. During anthesis, floral scent emission occurs in the pistillate and staminate stages. The effective pollinators were weevils (Sitophilus sp.) and beetles (Anomala sp.), while the role of Rove beetles (Aleochara sp.) and thrips (Thrips sp.) in pollination of M. ventii appears to be minor or absent. The major chemical compounds of the floral scents were Limonene, β-Pinene, α-Pinene, 1,8-Cineole, Methyl-2-methylbutyrate, p-Cymene, Methyl-3-methyl-2-butenoate and 2-Methoxy-2-methyl-3-buten, and the relative proportions of these compounds varied between the pistillate and staminate stages. Production of these chemicals coincided with flower visitation by weevils and beetles. The results of pollination experiments suggest that M. ventii is pollinator-dependent, and low seed set in natural populations is a result of insufficient pollen deposition. Thus, conservation of the species should focus on improving pollination service through the introduction of genetically variable individuals and increase in density of reproducing trees.

Corybas taliensis is an endangered terrestrial orchid, endemic to China. In this study, we assembled the complete chloroplast (cp) genome using Illumina pair-end sequencing data. The whole cp genome is 131,393 bp in length with 38.21% of GC content. It encodes 121 genes, including 38 tRNA genes, 8 rRNA genes, and 75 protein-coding genes. The phylogenetic tree based on 13 cp genomes of Orchidoideae suggested that C. taliensis is closely related to Rhizanthella gardneri. This study will pave the way to understand the genomic information and conservation of this endangered endemic orchid species.

Magnolia sinica is one of the most threatened trees endemic to Southeast Yunnan. Based on our investigations, only 52 individuals and eight populations are found in the wild. M. sinica has been categorized as Critically Endangered on the IUCN Red List and identified as a “Plant Species with Extremely Small Populations (PSESP)”. Its fruit/seed set is very low and seedlings are rarely found in the wild. It is hypothesized that it may encounter obstacles to reproductive success. This study, therefore, focuses on its reproductive biology, knowledge of which is essential for effective conservation. Flowers of this species are protogynous and nocturnal, and possess a two-day rhythm of sexual presentation. For the first night of anthesis, the flowers are in the pistillate stage during which tepals open at dusk and close approx. 1 h later (except for the open outer ones). They remain closed until the next afternoon, when flowers, now in the staminate stage, re-open and remain so until the tepals drop. Nocturnal beetles enter into the flowers and remain trapped throughout the night as the flower closes, during which time they feed on tepals. Pollen-gathering bees are found to visit the re-opened flowers and the beetles are released during this stage. Two species of Pleocomidae and Curculionidae beetles appear to be effective pollinators. M. sinica is a self-compatible, pollinator-dependent species, and its fruit/seed set can be significantly increased by hand-pollination. No functional seed dispersers have been found in its extant natural habitats. These findings suggest that it may face both pollination and seed disperser insufficiencies in its current fragmented habitats, which may account for its low regeneration. Here we propose conservation strategies based on our findings.

Of the genus Craigia, widespread in the Tertiary, only two relict species survived to modern times. One species is now possibly extinct and the other one, Craigia yunnanensis, is severely endangered. Extensive surveys have located six C. yunnanensis populations in Yunnan province, southwest China. Using fluorescent amplified fragment length polymorphism (AFLP), the genetic diversity and population structure of these populations were examined. It was found that genetic diversity of C. yunnanensis was moderate at the species level, but low at regional and population levels. Analysis of population structure showed significant genetic differentiation between Wenshan and Dehong regions, apparently representing two geographically isolated for long time refuges. There are also clear indications of isolation between populations, which, together with anthropogenically caused decline of population size, will lead to general loss of the species genetic variation with subsequent loss of adaptive potential. To conserve the genetic integrity of C. yunnanensis, we recommend that ex-situ conservation should include representative samples from every population of the two differentiated regions (e.g. Wenshan and Dehong). The crosses between individuals originated from different regions should be avoided because of a high risk of outbreeding depression. As all the extant populations of C. yunnanensis are in unprotected areas with strong anthropogenic impact, there is no alternative to reintroduction of C. yunnanensis into suitable protected locations.

Pollination and seed dispersal in angiosperms have long been investigated in order to understand the coevolution of plants and animals. However, the signals from flowers and/or seeds to attract pollinators and/or seed dispersers have received comparatively little attention. In this study, the pollination biology and seed dispersal of the vulnerable agarwood plant Aquilaria sinensis (Lour.) Gilg, a traditional medicinal plant in China, was studied in its natural distribution range. The reproductive tactics of A. sinensis were studied in detail by employing various tests dealing with fruit set and also seed dispersal. Dynamic headspace extraction followed by GC-MS analysis was also performed in order to reveal the composition of floral scent. The results showed that noctuids and pyralids are the most effective pollinators of pollinator-dependent A. sinensis. The main compounds of the floral scent were (E, E)-α-Farnesene (61.9 ± 3.2%), trans-Ocimene (16.6 ± 1.2%), and Benzyl salicylate (4.6 ± 1.1%). The results obtained from seed dispersal experiments indicate that hornets are effective seed dispersers and they may play an important role in long-distance seed dispersal of A. sinensis. Based on our findings, we recommend several protection methods for this threatened agarwood plant in China.

Approximately one fifth of the world's plants are at risk of extinction. Of these, a significant number exist as populations of few individuals, with limited distribution ranges and under enormous pressure due to habitat destruction. In China, these most-at-risk species are described as ‘plant species with extremely small populations’ (PSESP). Implementing conservation action for such listed species is urgent. Storing seeds is one of the main means of ex situ conservation for flowering plants. Spore storage could provide a simple and economical method for fern ex situ conservation. Seed and spore germination in nature is a critical step in species regeneration and thus in situ conservation. But what is known about the seed and spore biology (storage and germination) of at-risk species? We have used China's PSESP (the first group listing) as a case study to understand the gaps in knowledge on propagule biology of threatened plant species. We found that whilst germination information is available for 28 species (23% of PSESP), storage characteristics are only known for 8% of PSESP (10 species). Moreover, we estimate that 60% of the listed species may require cryopreservation for long-term storage. We conclude that comparative biology studies are urgently needed on the world's most threatened taxa so that conservation action can progress beyond species listing.

The giant tree rhododendron (R. protistum var. giganteum) is one of the most famous plants in China, and is critically endangered. As previous conservation efforts only focused on the two recorded populations of this variety, key issues regarding relatedness to R. protistum var. protistum still remain. Our field investigations and SSR analysis of the two varieties in China and Nepal suggest that the two varieties are not significantly different, and we suggest that limited conservation resources could be better used elsewhere given the numerous endangered plants urgently needing protection in China. We suspect that the problems we identified in this study will also apply to many other taxa in developing countries identified as endangered on the basis of incomplete information. Keywords: Rhododendron protistum var. giganteum, Conservation priority, Genetic structure

Magnolia sinica, distributed in Yunnan province of China, is a critically endangered (CR) species based on the IUCN Red List. Here we provide the complete chloroplast (cp) genome sequence of M. sinica. Its length is 159,443 bp with four sub-regions: 88,156 bp of LSC region and 18,748 bp of SSC region are separated by two IR regions (each 26,570 bp). The genome contains 79 CDSs, four rRNAs, and 30 tRNAs. Phylogenetic analysis of cp genome of M. sinica with previously reported chloroplast genomes shows that M. yunnanensis is a sister to M. sinica with high bootstrap value.

Long-term ecological and genetic studies in natural populations of tree species require marking techniques so that individuals can be re-visited over time, even in difficult terrain. Both GPS coordinates and physical labels have disadvantages that can make re-finding trees difficult. We tested passive and semi-active radio frequency identification (RFID) tags and readers as a means to relocate individual trees. Passive RFID tags do not provide a good solution because of low transmission power of hand-held readers and strong directionality. Semi-active RFID tags provide detection over longer distances, but also suffer from strong directionality. Active RFID tags promise an improvement over semi-passive tags, and could be evaluated in a future study. We conclude that RFID technology has the potential to improve the ability of researchers to locate individual trees repeatedly under natural conditions, and can be used in conjunction with other marking techniques such as physical tags and GPS coordinates.

Michelia coriacea, a critically endangered tree, has a restricted and fragmented distribution in Southeast Yunnan Province, China. The genetic diversity, genetic structure and gene flow in the three extant populations of this species were detected by 10 inter-simple sequence repeat (ISSR) markers and 11 simple sequence repeat (SSR) markers. Examination of genetic diversity revealed that the species maintained a relatively high level of genetic diversity at the species level (percentage of polymorphic bands) PPB = 96.36% from ISSRs; PPL (percentage of polymorphic loci) = 95.56% from SSRs, despite several fragmental populations. Low levels of genetic differentiation among the populations of M. coriacea were detected by Nei’s Gst = 0.187 for ISSR and Wright’s Fst = 0.090 for SSR markers, which is further confirmed by Bayesian model-based STRUCTURE and PCoA analysis that could not reveal a clear separation between populations, although YKP was differentiated to other two populations by ISSR markers. Meanwhile, AMOVA analysis also indicated that 22.84% and 13.90% of genetic variation existed among populations for ISSRs and SSRs, respectively. The high level of genetic diversity, low genetic differentiation, and the population, structure imply that the fragmented habitat and the isolated population of M. coriacea may be due to recent over-exploitation. Conservation and management of M. coriacea should concentrate on maintaining the high level of genetic variability through both in and ex-situ conservation actions.

Hibiscus aridicola (Malvaceae) is an endangered ornamental shrub endemic to the dry-hot valleys of Jinsha River in southwest China. Only four natural populations of H. aridicola exist in the wild according to our field investigation. It can be inferred that H. aridicola is facing a very high risk of extinction in the wild and an urgent conservation strategy is required. By using a modified biotin-streptavidin capture method, a total of 40 microsatellite markers were developed and characterized in H. aridicola for the first time. Polymorphisms were evaluated in 39 individuals from four natural populations. Fifteen of the markers showed polymorphisms with two to six alleles per locus; the observed heterozygosity ranged from 0.19 to 0.72. These microsatellite loci would be useful tools for population genetics studies on H. aridicola and other con-generic species which are important to the conservation and development of endangered species.

Buddleja colvilei Hook.f. & Thomson (Scrophulariaceae) is a threatened alpine plant with a distribution throughout the Himalayas, also used as an ornamental plant. The name Buddleja sessilifolia B.S. Sun ex S.Y. Pao was assigned in 1983 to a plant distributed throughout the Gaoligong Mountains, but the name was later placed in synonymy with B. colvilei in the Flora of China. In this study we sequenced the complete chloroplast (cp) genomes of two individuals of B. colvilei and three individuals of B. sessilifolia from across the range. Both molecular and morphological analysis support the revision of B. sessilifolia. The phylogenetic analysis constructed with the whole cp genomes, the large single-copy regions (LSC), small single-copy regions (SSC), inverted repeat (IR) and the nuclear genes 18S/ITS1/5.8S/ITS2/28S all supported B. sessilifolia as a distinct species. Additionally, coalescence-based species delimitation methods (bGMYC, bPTP) using the whole chloroplast datasets also supported B. sessilifolia as a distinct species. The results suggest that the B. sessilifolia lineage was early diverging among the Asian Buddleja species. Overall gene contents were similar and gene arrangements were found to be highly conserved in the two species, however, fixed differences were found between the two species. A total of 474 single nucleotide polymorphisms (SNPs) were identified between the two species. The Principal Coordinate Analysis of the morphological characters resolved two groups and supported B. sessilifolia as a distinct species. Discrimination of B. colvilei and B. sessilifolia using morphological characters and the redescription of B. sessilifolia are detailed here.