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Rhododendron longipedicellatum is a narrow endemic species and a subject of urgent demand in the domestic market and overseas. Its fascinating shapes, brilliantly gilvous flowers, and unusual flowering time endow this species with extremely high ornamental value. However, only five wild populations of R. longipedicellatum surviving in limestone hab...
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... The amount of gene flow between populations significantly affects their genetic structure and is a crucial indicator of how environmental changes, human meddling and population isolation will affect those (Wu et al., 2017). The calculated geographical distance (Median value of geographical distance= 50.69km) among the Rhododendron species is higher resulting in difficulty to transmit genes (pollen and seed) from one to another species (Ng & Corlett, 2000;Huang et al., 2017;Li et al., 2018). As a result, short-distance seed dispersal and distance-limited pollen movement could be responsible for the population divergence. ...
Ten rare, threatened, and endangered Rhododendron species were collected from different altitudinal ranges starting from 2247masl to 3580masl. of Eastern Himalaya (particularly Darjeeling Hills) were studied by polymerase chain reaction (PCR) using randomly amplified polymorphic DNA sequences (RAPD) to measure the degree of the genetic diversity and relationship among the species which are urgently needed to promote effective conservation and management activities. Initially, 19 decamer oligonucleotide primers were screened on ten samples for unambiguous and reproducible band patterns. Out of nineteen, six decamer oligonucleotide primers finally yielding the best results were selected and used for the analysis of present samples. Mean 61 alleles were amplified by using six primers, among ten samples. Total 126 were unique bands showing an average of 79.43% polymorphism. The Genetic Similarity Coefficient (GS) was ranging from 0.45455 to 0.93827. The present study shows an average low level of genetic diversity (PIC= 0.2096, Hs= 0.979, Ho= 0.986, Ht= 0.985, I= 3.973). The population of Rhododendron shows a negative value of inbreeding coefficients (Fis < 0) indicating heterozygotes produced by the population due to crosses happens in between genetically distant individuals but the value does not support that there is a chance of outbreeding depression and population bottleneck in recent future. Results of AMOVA show that variation among and within populations is 1% and 99% respectively. The mean inbreeding coefficient (Fst) within subpopulations is 0.006. A dendrogram based on RAPD markers using the neighbor-joining cluster analysis method produced from Jaccards estimates using Free Tree software divided nine (out of ten) Rhododendron species into two main sister groups this result also supported by Principal Coordinates Analysis (PCoA). The obtained RAPD analysis results also suggested that some rare, threatened, and endangered species of Rhododendron in the present study could maintain moderate levels of genetic diversity. STRUCTURE assessment (ΔK= 5) showed the selected species distributed distantly from each other and estimated that the R. falconeri genotype is the maximum level of admixture among the ten species. Results of Mantel's test show a positive correlation between geographical distance and genetic similarity or dissimilarity of ten Rhododendron species. Whereas the positive regression analysis value (R²= 0.0809) does not tally for the deep connection between geographical distance and genetic similarity or dissimilarity among the evaluated species. Based on the results, summarized that Rhododendron species of Eastern Himalaya are at a high risk of outcrossing depression, which will lead to a population bottleneck. Therefore, immediate conservation (in-situ and ex-situ) measures have to be taken for these rare, threatened, endangered, economically, and ethno-botanically important Rhododendron species.
... CDPs have evolved remarkable reproductive strategies to ensure species survival in challenging habitats. Sexual reproduction, particularly through pollination, represents a critical yet vulnerable stage in their life cycle (Li et al., 2018), with successful seed production being its ultimate objective. Despite the ecological significance of studying these reproductive adaptations, research is often hindered by the inaccessible nature of cliff habitats. ...
... High genetic diversity enhances evolutionary potential, while low diversity limits adaptability to environmental changes (Binks et al., 2015). For example, some CDP species, like C. acerifolia (Loṕez-Pujol et al., 2005;Zhao et al., 2023a), Asperula naufraga (Valli et al., 2021), and Antirrhinum subaeticum (Jimeńez et al., 2002), exhibit low genetic diversity, while others, such as O. taihangensis (Guo et al., 2013) and T. rupestris (Tang et al., 2010;Duan, 2013;Wang et al., 2011;Li et al., 2018), show higher diversity. Moreover, genetic diversity is influenced by factors such as cliff crevice variability (such as differences in size, depth, and microclimatic conditions), environmental pressures, seedling growth, pollen and seed dispersal, and reproductive biology (George et al., 2009;Neri et al., 2021;Zhao et al., 2023b). ...
Cliffs represent unique ecosystems that harbor diverse rare cliff-dwelling plants (CDPs), which play critical roles in enhancing biodiversity and maintaining ecological stability. Despite substantial advances in CDP research enabled by modern biological technologies, particularly in diversity assessment, taxonomic classification, and conservation strategies, the field lacks comprehensive syntheses of recent progress, impeding efficient identification of emerging research directions. This review systematically examines five key research domains: (1) The ecological and potential application value of CDPs; (2) cliff habitat ecology, focusing on abiotic factors such as microclimate, edaphic properties, and water conditions, as well as biotic components; (3) adaptive strategies of CDPs, encompassing morphological specializations, physiological resilience mechanisms, early growth stage, reproductive characteristics, molecular-level evolutionary adaptations, and genetic diversity patterns; (4) technological advancements in cliff research methodologies; and (5) CDP conservation strategies by conducting a comparative analysis between in situ protection measures and ex situ preservation approaches. Our review reveals three critical research gaps demanding immediate attention: the need for long-term ecological monitoring of cliff habitats and their microenvironmental dynamics, the imperative to understand CDPs’ physiological adaptations to extreme environments, and the necessity to elucidate molecular mechanisms governing plant-environment interactions within these unique ecosystems. Future research should prioritize the development of innovative tools, advanced technologies, and interdisciplinary methodologies to fill in existing knowledge gaps in the field. Such comprehensive efforts will not only elucidate the complex adaptation mechanisms of CDPs but also provide a scientific foundation for their effective conservation and ecosystem management.
... The pistils were slightly taller than or flush with the stamens. The stamens grew separately, and the number of stamens was approximately [30][31][32][33][34][35]. The filaments were separated from each other and were 15.98 ± 1.97 mm long and 0.72 ± 0.12 mm wide. ...
... This adaptability is reflected by the morphological characteristics of the flowers, the length of the flowering period, and pollination characteristics, among other aspects. The plant breeding system can be accurately classified based on the P/O value, OCI value, and results of bagging experiments 33 . In this study, the P/O value of C. speciosa was approximately 3107.52, which indicates obligate xenogamy. ...
Although Chaenomeles is widely used in horticulture, traditional Chinese medicine and landscape greening, insufficient research has hindered its breeding and seed selection. This study investigated the floral phenology, floral organ characteristics, palynology, and breeding systems of Chaenomeles speciosa (Sweet) Nakai. The floral characteristics of C. speciosa were observed both visually and stereoscopically. The microstructures of the flower organs were observed using scanning electron microscopy. Pollen stainability was determined using triphenyl tetrazolium chloride staining. Stigma receptivity was determined using the benzidine-H2O2 method and the post-artificial pollination pollen germination method. The breeding system was assessed based on the outcrossing index and pollen–ovule ratio. The flowers of C. speciosa were bisexual with a flowering period from March to April. The flowering periods of single flowers ranged from 8 to 19 d, and those of single plants lasted 18–20 d. The anthers were cylindrical, with the base attached to the filament, and were split longitudinally to release pollen. The flower had five styles, with a connate base. The ovaries had five carpels and five compartments. The inverted ovules were arranged in two rows on the placental axis. The stigma of C. speciosa was dry and had many papillary protrusions. In the early flowering stage (1–2 d of flowering), the pollen exhibited high stainability (up to 84.24%), but all stainability was lost at 7 d of flowering. Storage at – 20 °C effectively delayed pollen inactivation. The stigma receptivity of C. speciosa lasted for approximately 7 days, and the breeding system was classified as outcrossing with partial self-compatibility.
... Rhododendron (Ericaceae) is one of the largest genera of angiosperms, with important ornamental, cultural, scientific, economic, and medicinal values. There are over 1200 species of Rhododendron worldwide, over 900 of which are distributed in Asia and more than half of them in southwest China, which is the distribution and evolution center of Rhododendron plants in modern times [10][11][12][13][14]. Guizhou is located at the edge of the center and the transition zone of its eastward spread and is home to more than 110 naturally distributed Rhododendron species, second only to Yunnan, Sichuan, and Tibet [15,16]. ...
... According to the population dynamics prediction of R. irroratum (Table 4), the population sizes of R. irroratum in communities I b , II b , and III b will decrease from the current numbers of 126, 172, and 90 plants to 12,21, and 10 plants in six years. Similarly, the quantities of R. irroratum in communities I b , II b , and III b all showed a trend of gradual increase after two, four, and six years at each age class, except for age class ii. ...
To explore the population structures and dynamics of Rhododendron shrub communities at different stages of succession in northwest Guizhou, China, this study examined the populations of Rhododendron annae and Rhododendron irroratum shrub with two different stages. A space-for-time substitution was employed to establish the diameter class/height structures, static life tables, and survival/mortality rate/disappearance rate curves of both Rhododendron populations with different orders of succession. Their structural and quantitative dynamics were analyzed, and their development trends were predicted. The results showed that, quantitatively, the populations of R. annae and R. irroratum in the two Rhododendron communities with different orders of succession were dominated by age classes one, two, and three as well as height classes i, ii, and iii. The number of Rhododendron plants at the three age classes and the three height classes accounted for 97.61–100% of the total. The quantitative dynamic indices of R. annae and R. irroratum were both greater than 0, with and without considering external interference. In terms of age class and height structures, both Rhododendron populations were expanding populations, presenting “inverted-J-shaped” and irregular pyramid patterns. There was a sufficient number of young individuals, but few or no old individuals. Both survival curves of the populations of R. annae and R. irroratum in the two Rhododendron communities with different orders of succession belonged to the Deevy-II type. In the late stage of succession, the mortality curves and disappearance curves of both Rhododendron populations in these communities presented a trend of increasing first and then decreasing with increasing age class. This result indicates that at each age class, R. annae and R. irroratum showed a trend of gradual increase after two, four, and six years. In brief, the populations of R. annae and R. irroratum have rich reserves of seedlings and saplings, but high mortality and disappearance rates. In this context, it is necessary to reduce human interference and implement targeted conservation measures to promote the natural renewal of Rhododendron populations.
... Rhododendron is one of the largest genera of angiosperms with more than 1200 species worldwide, which have important ecological and socio-economic applications of ornamental, cultural, scientific, economic, and medicinal value (MacKay and Gardiner, 2017;Li et al., 2018;Ahmad et al., 2021). The genus is mostly distributed in subtropical evergreen broad-leaved mountain forests, mixed coniferous broad-leaved forests, coniferous forests, and dark coniferous forests at altitudes varying from 1000 to 3800 m (Fang and Min, 1995). ...
Tree base sprouting is the main reproduction and expansion mode of Rhododendron plants. By leveraging the plot survey method, the species composition, community renewal, and species diversity in three Rhododendron shrub communities in control, and before and after clearcutting (CK, D3yr, and D6yr, respectively) were studied. Moreover, the dissimilarity of Rhododendron communities in CK, D3yr and D6yr were analyzed. The results showed that there were 26 plant species belonging to 14 families and 22 genera, in 3 communities in total, with 19 species of shrub plants and 7 species of herbaceous plants. The number of species increased from 13 in CK to 23 in D3yr and then decreased to 20 in D6yr. The height and coverage of D3yr and D6yr reached 39.3% and 58.9% of that of CK, respectively. The relative height of CK, D3yr, and D6yr was 43.79%, 65.4%, and 58.54%, respectively. The coverage of D3yr and D6yr reached 60.8% and 114.70% of that of CK, respectively. The relative coverage of CK, D3yr, and D6yr was 19.05%, 83.24%, and 77.32%, respectively. The important value of Rhododendron plants in the communities increased from 0.42 in CK to 0.74 in D3yr, and then decreased to 0.67 in D6yr. The α diversity in the shrub layer of D3yr and D6yr were generally lower than those of CK except Pielou evenness index. The β diversity indicates that the similarity between CK and D3yr was lower, that between CK and D6yr was moderate, and that between D3yr and D6yr was higher. The sprouting height and coverage of Rhododendron plants was significantly correlated with age and sprouting time. The sprouting ability of Rhododendron plants increased first and then decreased with age, while the sprouting ability of Rhododendron plants with age of 10–12 years was the strongest. Clearcutting measures can improve the dominance of Rhododendron plants in the communities, promote the sprouting and renewal of Rhododendron population, and accelerate the succession rate of communities.
... Rhododendron is the collective name for Rhododendron (Ericaceae) plants, and of its flowers are among the ten most recognizable flowers in China. In addition to its high ornamental value, rhododendron also serves the purposes of ecological conservation, medical application, and scientific research (Li et al. 2018, Zhang et al. 2021. Rhododendron contains more than 1,000 species and has a global distribution. ...
... Additionally, outcrossing organisms typically exhibit higher genetic variety than selfing species (Nybom 2004, Zhang et al. 2021. Previous research revealed that Rhododendron requires pollinators and produces adhesive pollen, suggesting that relies mostly on outcrossing (Ng and Corlett 2000, Huang et al. 2017, Li et al. 2018. The high genetic diversity of the four populations of Rhl might also be derived from their ancestral populations, as observed for other threatened Rhododendron plants, e.g., R. protistum var. ...
... To undertake scientifically informed management measures, understanding the reproductive biology of endangered species is crucial for conservation and sustainable utilization of biodiversity (Fiser et al. 2021). Reproductive biology captures the most critical stages of species' life cycle, and helps in understanding species' life histories, ecological interactions and evolutionary processes (Li et al. 2018). The ability of plant species to successfully inhabit a variety of habitats across its distribution range largely depends on the reproductive traits (Barrett et al. 2008). ...
... The ability of plant species to successfully inhabit a variety of habitats across its distribution range largely depends on the reproductive traits (Barrett et al. 2008). Therefore, the study of reproductive biology of a plant species is crucial for exploring the mechanism by which it has become endangered (Li et al. 2018). Details about reproductive biology and ecology aspects helps in identifying the bottlenecks that hinder the propagation of species in their natural populations, and therefore knowledge about reproduction is important to devise suitable conservation programs for endangered species (Marbaniang et al. 2018). ...
In this study, we investigated the reproductive biology of Trillium govanianum — a medicinally important endangered plant species endemic to the Himalaya. We specifically aimed to unravel the key floral traits that aid and/or limit the species’ reproduction, including the breeding strategies and modes of pollination. We studied qualitative and quantitative floral traits, and conducted different breeding experiments to understand reproductive biology of this plant species for its conservation and sustainable utilization. Our results show no temporal separation between anther dehiscence and stigma receptivity in the species, though essential organs are spatially separated. The absence of nectar secretion in the flowers and lack of pollenkitt in the pollen wall indicates anemophily is operative in the species; nevertheless, some flies and beetles were observed to occasionally visit the plants. The pollen/ovule ratio indicates a value between facultative-xenogamy to xenogamy. Our pollination experiment results reveal that the species undertakes both self- and cross-pollination. We observed a significant difference in fruit set between the supplemented and open-pollinated controls, indicating that the species might be pollen-limited. Although both self- and cross-pollinations are operating in the species, yet the fruit set was low, which may be due to the inefficient pollination system and meiotic abnormality found in the species. Overall, our results suggest that the reproduction in T. govanianum is limited by some inherent biological traits in combination with environmental conditions. Looking ahead, we highlight how our findings can help in guiding conservation of this endangered species in the Himalaya.
... Rhododendron is the collective name of Rhododendron (Ericaceae) plants and is one of the top 10 famous flowers in China. In addition to its high ornamental value, rhododendron has the functions of ecological protection, medicinal use, and scientific research (Liang et al. 2016;Li et al. 2018). There are abundant rhododendron germplasm resources in China. ...
Rhododendron henanense subsp. lingbaoense is endemic in China. The cpDNA of R. henanense subsp. lingbaoense is a typical quadripartite structure with a length of 208,015 bp, including a large single-copy region of 110,593 bp and a small single-copy region of 2606 bp separated by a pair of identical inverted repeat regions of 47,408 bp each. The chloroplast genome contains 119 genes, including 86 protein-coding genes, four ribosomal RNA genes, and 29 transfer RNA genes. The phylogenetic analysis of R. henanense subsp. lingbaoense showed a relatively close relationship with Rhododendron delavayi.
... In addition, genetic diversity is usually higher in outcrossing species than in selfing species (Hamrick, 1990;Nybom, 2004). Previous studies found that Rhododendron have adhesive pollen and require pollinators, indicating that Rhododendron may primarily rely on outcrossing (Ng and Corlett, 2000;Ma et al., 2015;Huang et al., 2017;Li et al., 2018). Our field surveys indicate that the primary pollination mode of R. meddianum is cross-pollination by insect (mainly Bombus spp.) and birds. ...
... The distance among the populations in this study was more than 50 km, which hardly allows gene flow (pollen or seeds) between populations. Previous studies have indicated that the seed dispersal distance of Rhododendron species ranges from approximately 30e80 m (Ng and Corlett, 2000), and its pollen can be transmitted by bees and birds with dispersal distance of 3e10 km of (Ng and Corlett, 2000;Huang et al., 2017;Li et al., 2018). In addition, in line with our observation, seedlings grow sporadically around the parent tree. ...
Rhododendron meddianum is a critically endangered species with important ornamental value and is also a plant species with extremely small populations. In this study, we used double digest restriction-site-associated DNA sequencing (ddRAD) technology to assess the genetic diversity, genetic structure and demographic history of the three extant populations of R. meddianum. Analysis of SNPs indicated that R. meddianum populations have a high genetic diversity (π = 0.0772 ± 0.0024, HE = 0.0742 ± 0.002). Both FST values (0.1582–0.2388) and AMOVA showed a moderate genetic differentiation among the R. meddianum populations. Meanwhile, STRUCTURE, PCoA and NJ trees indicated that the R. meddianum samples were clustered into three distinct genetic groups. Using the stairway plot, we found that R. meddianum underwent a population bottleneck about 70,000 years ago. Furthermore, demographic models of R. meddianum and its relative, Rhododendron cyanocarpum, revealed that these species diverged about 3.05 (2.21–5.03) million years ago. This divergence may have been caused by environmental changes that occurred after the late Pliocene, e.g., the Asian winter monsoon intensified, leading to a drier climate. Based on these findings, we recommend that Rhododendron meddianum be conserved through in situ, ex situ approaches and that its seeds be collected for germplasm.
... This result was different from the other two plants distributed in karst limestone regions of southwest China. Rhododendron longipedicellatum was primarily pollinated by Bombus braccatus (Li et al., 2018) and Apis cerana was the only efficient pollinator of Bulbophyllum ambrosia (Chen & Gao, 2011). Both of these two species have a high flower visiting frequency. ...
Camellia pubipetala is an endemic and endangered species with small and isolated populations occurring only in karst regions in Guangxi of south China. To understand the reproductive biology of C. pubipetala and its possible influences upon its endangered status, its breeding system and pollination ecology were studied in the Longhushan (LHS) and Longzhao (LZ) populations of this species. The flowering duration of the C. pubipetala populations spanned from late January to early April and anthesis of a single flower usually lasted 5–7 days. This species is homogamous, and the pollen and stigma are viable throughout anthesis. Each bagged flower could secrete 141.5 μL of nectar at a sugar concentration of 25.0% during anthesis. The observed high pollen/ovule ratio, and the results of hand‐pollination experiments indicated that this species obligately outcrosses. Open pollination resulted in a significantly decreased fruit set (6.7%) and seed set (38.9%) compared to supplementary pollination treatment (23.3% and 64.7%, respectively), which is indicative of a pollen limitation in the process of pollination. The primary pollinator of C. pubipetala is the sunbird Aethopyga christinae and its visiting frequency is quite low, whereas the honeybee Apis cerana is only an occasional pollinator in wild populations. Low reproductive rates in C. pubipetala were found to be a consequence of few species of pollinators and their low visiting frequency. Pollen limitation may be a crucial factor that contributes to the endangered nature of this species. Artificial pollination and the release of pollinators are effective ways to increase the fruit and seed yield of this species. The primary pollinator of Camellia pubipetala is the sunbird Aethopyga christinae, and its visiting frequency is quite low, whereas the honeybee Apis cerana is only an occasional pollinator in wild populations. Pollen limitation may be a crucial factor that contributes to the endangered nature of this species.
