Background and Aims Distylous polymorphisms (distyly) are adaptations for plants to improve efficiency of cross-pollination and reduce pollen wastage. Theoretical models suggest that distyly evolves from stylar monomorphism via an intermediate stage of stigma-height dimorphism (SHD), however, this evolutionary scenario is only observed in few distylous lineages. The genus Jasminum have many species exhibit either distyly or SHD, providing an ideal opportunity to test models of the evolution of distyly. Focusing on the evolution of distyly, we investigated floral morphs and evaluated the occurrence of distyly and SHD in Jasminum using phylogenetic reconstruction and morphological analysis. Methods We investigated floral morphs and evaluated the occurrence of distyly and stigma-height dimorphism through morphology observation. To perform phylogenetic analysis, we sequenced plastomes of forty species from Jasminum and Chrysojasminum using Illumina next generation sequencing, and then constructed phylogenetic tree using maximum likelihood method and Bayesian inference. Based on the phylogenetic tree, we inferred the ancestral floral type through ancestral reconstruction. Key Results Our results suggest that the distyly originated in the common ancestor of Jasminum and Chrysojasminum . SHD occurs in several Jasminum species scattered in different clades of the phylogenetic tree, suggesting multiple independent reversions from distyly back to SHD. However, this transition is not associated with the loss of ancillary polymorphisms, as all the species examined in this study well retain dimorphic traits for other floral organs such as pollens and stigmas. Moreover, most species maintain strict heteromorphic self-incompatibility, while J. officinale has lost or at least partially lost self-incompatibility, suggesting that distyly is not always linked to self-incompatibility. Conclusions In Jasminum , breakdown of distyly resulted in evolutionary transitions to stigma-height dimorphism for multiple times, suggesting that distyly is not a stable floral polymorphism under certain selective forces. These findings advance our understanding on the evolution of distyly and plant reproductive systems.

Heterostyly is a floral polymorphism controlled by an S-locus supergene in several angiosperm families. Most heterostylous species are self-incompatible. Here, we investigate the genomic architecture of distyly in self-compatible Cordia subcordata in which incompatibility has apparently been lost. We assembled chromosome-level genomes of floral morphs and conducted population genomic analyses to locate the S-locus region. We used transcriptomic analyses of floral organs and functional validation by gene overexpression to identify genes controlling floral dimorphism. The tempo and mode of origin of S-locus genes was also investigated to determine whether gene duplication facilitated supergene assembly. The candidate S-locus in C. subcordata contained 12 genes, eight of which were restricted to the S-morph. CsGA2ox6 deactivates gibberellins and was exclusively expressed in S-morph pistils. Overexpression of CsGA2ox6 in transgenic tobacco produced flowers with shortened styles and an apparently functioning self-incompatibility system. The genomic locations of paralogs and estimations of duplication age suggested that the S-locus genes may have arisen through stepwise duplications, although an origin via segmental duplication could not be excluded. Our study revealed molecular convergence with several other distylous families in hemizygous structure and possibly in the mode of supergene origins. We also identified a molecular pathway for style-length control, likely through gibberellin deactivation by CsGA2ox6, which may have also controlled the expression of self-incompatibility in transgenic plants.

ABSTRACT Subtropical China, dominated by evergreen broad‐leaved forests, harbors exceptionally rich and highly endemic plant diversity, yet the evolutionary history of its understory herbs remains poorly understood. Here, we investigated Burmannia nepalensis, a fully mycoheterotrophic herb endemic to these forests, to uncover the evolutionary and demographic processes shaping understory biodiversity. Using plastome sequences and nuclear microsatellite loci, we examined spatial patterns of genetic variation across 20 populations. The species exhibited low within‐population genetic diversity but pronounced genetic differentiation among populations. Geographic isolation and historical climatic fluctuations emerged as the main drivers of population divergence. Concordant phylogeographic patterns from plastid and nuclear markers, together with species distribution modeling, suggest that B. nepalensis persisted in multiple glacial refugia during the Last Glacial Maximum (LGM), particularly in the Nanling Mountains, Wuyi Mountains, and southwestern karst regions. Demographic reconstructions indicate population expansion after the LGM, followed by a decline in effective population size approximately 3000 years before present (BP), likely driven by human‐induced habitat fragmentation. Our findings highlight the combined roles of geography and climatic history in structuring genetic diversity in fully mycoheterotrophic plants, provide evidence for multiple northern refugia, and underscore the vulnerability of forest‐dependent understory herbs in subtropical China.

The cytogenetics of Cheniella, a recently segregated genus of the early-diverging subfamily Cercidoideae of Leguminosae, remain understudied, hindering our understanding of the cytological evolution and the utilization of this important plant group. Here we conducted comparative cytogenetic studies on 11 species and one subspecies of Cheniella and one species of its sister genus Phanera. Unlike earlier reports which recovered 2n=28 for two Cheniella species, we consistently observed chromosome counts of 2n=26 for all 11 species of Cheniella, supporting the segregation of Cheniella from Phanera, which consistently exhibited 2n=28 in this and previous studies. Our analyses, along with previous cytogenetic data, indicates that 2n=14, 2n=26 and 2n=28 are the predominant chromosome numbers in the basal-most genus Cercis, Cheniella and the remainder genera, respectively. The ancestor of the subfamily is most probably a diploid with 2n=14, with subsequent polyploidization followed by chromosome reduction events leading to 2n=28 and 2n=26 in the other lineages. Our results provide new insight into the cytotaxonomy and chromosome evolution of Cercidoideae, also lay the foundation for future genomics research.

Urban systems, particularly botanical gardens, often comprise a lot of exotic plant species that can integrate into local plant-pollinator networks, influencing their temporal structural dynamics. However, revealing how plant-pollinator interactions are continuously reshaped and how the roles of native plant and exotic plant species within networks alter over time remains a significant challenge. Here, we reconstructed monthly plant-pollinator interaction networks for 12 months within an urban botanical garden. We focused on the monthly variations in the structure of pollination networks and the roles of native and exotic plant species. The results showed that the dynamics of plant-pollinator interactions are characterized by significant changes in network structure and species alternations, which have substantial impacts on community processes. Each month, the plant-pollinator network can be divided into several modules of closely interacting plants and pollinators, and these modules form complex fission-fusion dynamics across the year. Monthly dynamic changes in plant-pollinator network structure led to alternations of plant species occupying core positions within the networks. The core plant species in the pollination networks alternated between native and exotic species across the 12 months, suggesting that plant species can be core species independently of their origin in urban plant-pollinator networks. Therefore, the roles of native and exotic plant species in plant-pollinator networks can only be fully detected and understood from the perspective of time-scale dynamics. These results suggest that information on the dynamic changes in plant-pollinator network structure is critical for understanding the temporally varying role of core species in urban ecosystems.

Pollination is an important ecological process for plant reproduction. Understanding the differences in plant–pollinator interactions and pollinator importance across spatial scales is vital to determine the responses of these interactions to global changes. Continental and oceanic island systems provide us with an ideal model to examine the variation in plant–pollinator interactions. Here, we compared the differences in species composition, plant–pollinator network structure, and pollinator importance in communities between a continental island (Wanshan Island) and an oceanic island (Yongxing Island) in China. The results reveal highly dissimilar species composition between continental and oceanic islands that caused highly different plant–pollinator network structures. In particular, the oceanic island networks had higher network connectance, nestedness, and specialization than the continental island networks. For plants cooccurring on both islands, pollinator species richness and flower visitation rate were higher on the continental island than on the oceanic island. Plant niche overlap was higher on the oceanic island than on the continental island, while pollinator niche overlap was higher on the continental island than on the oceanic island in both the entire network and cooccurring plant species subnetwork. Hymenoptera was the most important pollinator group in the continental island community, while Apidae was the most important in the oceanic island community. The results imply that oceanic island communities may be less vulnerable to disturbance, such as habitat alteration or destruction, than continental island communities and provide implication insights into biodiversity conservation for pollinators on islands.

•The assembled genome of Bay cedar is 292.8 Mb, representing a small genome size within Fabales.•The compact genome was likely caused by remarkable reduction of long terminal repeat retrotransposons and gene losses.•The genes related to cold tolerance and pest/pathogen resistance were largely lost.•Expanded, positively selected, or retained genes after WGD may drive Bay cedar's adaptation to tropical coral islands.•Differentially expressed genes under salt and drought stresses were particularly identified in the abscisic acid pathway.

Heterostyly is a polymorphic floral adaptation controlled by supergenes. The molecular basis of distyly has been investigated in diploid species from several unrelated families, but information is lacking for polyploid systems. Here, we address this knowledge gap in Schizomussaenda henryi, a tetraploid distylous species of Rubiaceae, the family with the greatest number of heterostylous species. Using chromosome-level genome assemblies and transcriptome profiling, we characterized its tetraploid genome, identified the S-locus region, and performed evolutionary analysis. The S-locus contains four hemizygous genes in the S-morph. SchzAUX22 emerged as a candidate gene potentially regulating both style length and filament growth via auxin signaling. Phylogenetic and k-mer-based analysis suggested a hybrid allopolyploid origin for S. henryi, while no subgenome dominance was detected. Results from the comparison of Ks values indicated that S-locus formation likely occurred through stepwise duplications. This study provides the first comprehensive genomic analysis of distyly in a polyploid species and demonstrates that the S-locus remains intact despite allopolyploidization resulting from hybridization. Our results indicated that polyploidization does not necessitate the breakdown of distyly, which occurs in several other heterostylous lineages.

A new species, Ticanto xylocarpa K. W. Jiang & Shi J. Li is described and illustrated here. It is superficially similar to T. magnifoliolata in its leaf shape and ferruginous young branches and inflorescence axes. However, it is readily distinguished by the ligneous and wingless pods that are dehiscent when mature. Calculations of Area of Occupancy (AOO) and Extent of Occurrence (EOO) suggest that Ticanto xylocarpa meets the criteria for Least Concern (LC) in the IUCN Red List.

Abstract Heterospecific pollen (HP) deposition varies widely among species in communities, which has been explicated by two adaptation strategies: HP avoidance and HP tolerance. Studies of the plant–pollinator network have uncovered that oceanic island communities are highly generalized and strongly connected. It remains unclear, however, which strategy prevails in such communities. We examined stigma pollen deposition on 29 plant species, and assessed patterns of HP load size and diversity in the Yongxing Island community. We assessed the effects of phenotypic specialization and species‐level network structural properties of plant species on pollen deposition among species. The hypothesis of three accrual patterns of HP within species was tested by illustrating the relationship between conspecific pollen (CP) and HP receipt. Extensive variation occurred among species in HP receipt, while 75.9% of species received less than 10% HP and one species received more than 40% HP throughout the community. Flower size strongly drives the variation of HP receipt, while network structural properties had no effect on the pollen receipt. Nineteen species showed no relationship between the number of HP and CP loads, and they received smaller HP load sizes and lower HP proportions. Most plant species evolved HP avoidance strategy, and HP receipt was an occasional event for most plant species in the generalized community. HP and CP receipts are independent of each other in plant species with the HP avoidance mechanism. Our results highlight that plants in the generalized pollination system may preferentially select to minimize the HP load on stigmas.

Phyllosphere fungi exhibit a wide range of species and play a pivotal role in island ecosystem biodiversity. They bolster plant resilience against diseases and environmental stresses, facilitate the decomposition of organic materials, and enhance nutrient exchange between plants and their surroundings. Despite extensive research on island biogeography pertaining to flora and fauna, the assembly of phyllosphere fungal communities has not been thoroughly explored. This study addresses this gap by employing high-throughput sequencing to examine phyllosphere fungi associated with three island plant species (Messerschmidia argentea, Morinda citrifolia, and Suriana maritima) across 13 islands in the Xisha Islands region. Our findings reveal significant variances in fungal α-diversity and community composition across different islands, plant species, and functional guilds. The variation in fungal α-diversity was notably correlated with the geographical distance from the mainland and a satellite-derived vegetation index, while the Bray-Curtis similarity in fungal communities was primarily influenced by the geographical distance between islands. Stochastic elements, particularly dispersal limitation and drift, were identified as major drivers of fungal community assembly. Furthermore, we observed that island size impacts the distribution of potential keystone species and their co-occurrence patterns within the fungal groups. Intriguingly, host vegetation was found to exert a stronger selective influence on phyllosphere fungi than island characteristics. These results provide valuable insights into the complex ecological interactions and processes governing fungal communities in isolated and unique environmental settings.

Plant-pollinator interactions play a vital role in the maintenance of biodiversity and ecosystem function. Geographical variation in environmental factors can influence the diversity of pollinators and thus, affect the structure of pollination networks. Given the current global climate change, understanding the variation of pollination network structure along environmental gradients is vital to predict how global change will affect the ecological interaction processes. Here, we used a global plant-pollinator interaction data collection by the same sampling method at the same period to explore the effects of elevation, latitude, and plant richness on the structure and robustness of pollination networks. We analyzed a total of 87 networks of plant-pollinator interactions on 47 sites from 14 countries. We conducted a piecewise structural equation model to examine the direct and indirect effects of elevation, latitude, and plant richness on the network robustness and analyzed the function of network structure in elucidating the relationship between robustness and these gradients. We found that plant richness had both positive effects on robustness under random and specialist-first scenarios. Elevation, latitude, and plant richness affected network connectance and modularity, and ultimately affected network robustness which were mediated by nestedness under specialist-first and random scenarios, and by connectance under the generalist-first scenario. This study reveals the indirect effects of elevation, latitude, and plant richness on pollination network robustness were mediated by nestedness or connectance depended on the order of species extinctions, implying that communities with different pollination network structures can resist different extinction scenarios.

Background Gene transfer between the plastid and mitochondrial genomes has been reported in several lineages of the legume family (Leguminosae or Fabaceae). However, it is not clear whether these events happened in other families of the order Fabales. We herein generated a high-quality mitochondrial genome of Suriana maritima in the family Surianaceae, which is closely related to Leguminosae and distributed mainly in extreme environments of tropical coral islands, to understand the gene transfers between orgenelle genomes of S. maritima and the structural and functional evolution of mitogenomes in Fabales. Results We combined Illumina and Nanopore technologies to assemble the mitogenome of S. maritima . The mitogenome was 458,738 bp in length and contained 39 protein-coding, three ribosomal RNA, and 20 transfer RNA genes. A number of sequences derived from the chloroplast genome of S. maritima were detected in the mitogenome, including 41 plastid genes among 83 mitochondrial plastid DNA sequences with a total length of 30,834 bp. Transferred genes accounted for 18.8% of the plastid genome and 6.7% of the mitogenome, and these estimates were much higher than those in previous studies of Fabales. Conclusions In addition to providing a high-quality mitogenome of an additional species in Fabales and the first species in Surianaceae, S. maritima , our findings advance our understanding of gene transfer between organelle genomes.

Consisting of trees, climbers and herbs exclusively in the intertidal environments, mangrove forest is one of the most extreme and vulnerable ecosystems of our planet and has long been of great interest for biologists and ecologists. Here, we first assembled the chromosome-scale genome of a climber mangrove plant, Dalbergia candenatensis. The assembled genome size is approximately 474.55 Mb, with a scaffold N50 of 48.1 Mb, a complete BUSCO score of 98.4%, and a high LTR Assembly Index value of 21. The genome contained 283.46 Mb (59.74%) repetitive sequences, and 29,554 protein-coding genes were predicted, of which 87.54% were functionally annotated in five databases. The high-quality genome assembly and annotation presented herein provide a valuable genomic resource that will expedite genomic and evolutionary studies of mangrove plants and facilitate the elucidation of molecular mechanisms underlying the salt- and water-logging-tolerance of mangrove plants.

Subfamily Cercidoideae is an early-diverging lineage of Leguminosae, within which the number and classification of genera have been controversial. Cheniella is a recently described genus in the Cercidoideae which requires revision and testing of its monophyly and circumscription. Here we infer the phylogenetic position and infrageneric relationships of Cheniella as well as the intergeneric relationships of Cercidoideae using 48 newly sequenced plastid genomes, including 34 individuals representing all species of Cheniella. Our phylogenetic analyses yield a well-resolved tree of Cercidoideae with robust support at most nodes. We also present morphological studies through field work and herbarium studies to re-assess the classification and circumscription of the genus. Based on the results of molecular analyses and morphological studies combined with distribution data, we broaden the circumscription of Cheniella to comprise a total of 15 species and 3 subspecies, including three new species (C. hechiensis, C. longistaminea, C. pubicarpa), one new combination (C. tianlinensis) and one new status and combination (C. longipes).

AbstractWendlandia, as currently circumscribed, is a genus of Rubiaceae comprising about 90 species mainly in tropical and subtropical Asia. By sampling species from all four series (Clavigerae, Euexsertae, Montigenae, Subinclusae) and all tribes in the subfamily Dialypetalanthoideae, we examined the monophyly of Wendlandia based on phylogenetic reconstruction using the nuclear ribosomal internal transcribed spacer and four plastid DNA regions. Wendlandia was resolved as biphyletic, consisting of two distantly related lineages that correspond to the monotypic series Clavigerae (Wendlandia pendula), sister to the Chinese endemic genus Trailliaedoxa, and a clade containing the remainder sampled members of Wendlandia. Based on the isolated phylogenetic position of W. pendula and its unique morphological characteristics compared to the recognized tribes of the Vanguerieae alliance, we herein erect a new monotypic genus, Clavistigma, and a new tribe, Clavistigmateae to accommodate the unique species. The secondary pollen presentation and the unique seed morphology were firstly described for the species. The divergence time between Clavistigma and Trailliaedoxa was dated back to 13.8 mya, coinciding with the climate change in northwestern Yunnan driven by the uplift Tibet Plateau and the river incision in the Hengduan Mountains during the Miocene and Late Pliocene.

Ectomycorrhizal fungi (EMF) can form symbiotic relationships with plants, aiding in plant growth by providing access to nutrients and defense against phytopathogenic fungi. In this context, factors such as plant assemblages and soil properties can impact the interaction between EMF and phytopathogenic fungi in forest soil. However, there is little understanding of how these fungal interactions evolve as forests move through succession stages. In this study, we used high-throughput sequencing to investigate fungal communities in young, intermediate, and old subtropical forests. At the genus level, EMF communities were dominated by Sebacina , Russula , and Lactarius , while Mycena was the most abundant genus in pathogenic fungal communities. The relative abundances of EMF and phytopathogenic fungi in different stages showed no significant difference with the regulation of different factors. We discovered that interactions between phytopathogenic fungi and EMF maintained a dynamic balance under the influence of the differences in soil quality attributed to each forest successional stage. The community composition of phytopathogenic fungi is one of the strong drivers in shaping EMF communities over successions. In addition, the EMF diversity was significantly related to plant diversity, and these relationships varied among successional stages. Despite the regulation of various factors, the positive relationship between the diversity of phytopathogenic fungi and EMF remained unchanged. However, there is no significant difference in the ratio of the abundance of EMF and phytopathogenic fungi over the course of successions. These results will advance our understanding of the biodiversity–ecosystem functioning during forest succession. Key points • Community composition of both EMF and phytopathogenic fungi changed significantly over forest succession. • Phytopathogenic fungi is a key driver in shaping EMF community. • The effect of plant Shannon’s diversity on EMF communities changed during the forest aging process.

Based on examination of relevant literature and herbarium specimens, we designate a lectotype for Bauhinia esquirolii Gagnep., the basionym of Phanera esquirolii (Gagnep.) Sinou & Bruneau. We also synonymize P. comosa (Craib) Bandyop. & Ghoshal under P. esquirolii and provide an emended description of the latter.

We describe here a rare, critically endangered new species of the genus Cheniella from Guangdong province of southern China. Cheniella tsoongii is morphologically similar to C. corymbosa, and can be distinguished by having a combination of deeply-bilobed hairy leaves, white flowers, shorter hypanthia, yellow anthers, and densely ferruginous-tomentose inflorescence rachides, pedicles and hypanthia. We suggest assessing the conservation status of the species as Critically Endangered (CR) as it possesses an extremely high risk of extinction based on the rapid population declines during the last century and, only no more than 10 individuals remain in an environmentally unprotected area now. Urgent conservation studies and actions are necessary to prevent the extinction of this species.

Mycoheterotrophs are non-photosynthetic plants that obtain all of their carbon requirements through parasitizing mycorrhizal fungi. They originated from the autotrophic ancestors and usually have more specific relationships with fungi than that of green plants, for reasons that are largely unknown. Determining the factors that lead to specificity in mycoheterotrophs could provide insights on the constraints to mycoheterotrophic evolution. Here we assess the fungal diversities in mycoheterotrophic plants and their co-occurring plants to determine the roles of ecological factors on the specific fungal associations in mycoheterotrophic plants. We investigated mycorrhizal fungal communities in 16 populations of seven Burmannia species with different trophic modes and their co-occurring plants using high-throughput sequencing to assess the tripartite relationships of fungi, mycoheterotrophs and co-occurring autotrophs. We found that mycoheterotrophic species have similar fungal richness to their chlorophyllous relatives, indicating that they are not associated with a reduced set of fungal partners. The preference of mycoheterotrophic species toward specialized fungal assemblages is consistent with the pattern found in the green autotrophic plants within forest habitats, suggesting a coupling of the fungal phylogenetic constraints between mycoheterotrophs and their co-occurring autotrophs. We furthermore show that the turning to fungal communities having closer phylogenetic relationships during habitat shifts from open grasslands to shaded forests might provide the basis for the specialization of mycorrhizal associations in mycoheterotrophic species of Burmannia. Our findings suggest that fungal niche shifts may have promoted fungal partner changes and specialization in mycoheterotrophic plants. Our results provide new insights into the ecological factors leading to the specialized interactions between mycoheterotrophic plants and their fungal partners, expanding our understanding of the evolutionary trajectories followed by mycoheterotrophs.Read the free Plain Language Summary for this article on the Journal blog.