American Journal of Botany

AO_SCPLOWBSTRACTC_SCPLOWMulti-species communities of epiphytic bromeliads are a defining component of Neotropical canopies, yet we have little knowledge of how closely related species differ in the balance struck among vegetative growth, clonal propagation, and sexual reproduction. We compared reproductive output, clonality, and sexual systems in sympatric populations of Catopsis nutans (Sw.) Griseb. and Catopsis sessiliflora (Ruiz & Pav.) Mez occupying citrus groves in central Belize, sampling 235 reproductively mature individuals across 138 host trees in nine groves. Reproductive output, measured as the count of reproductive structures per individual, was modeled with negative binomial generalized linear mixed models that accounted for vegetative size and host tree identity. All sampled C. nutans were hermaphroditic, whereas all C. sessiliflora were unisexual, representing a dioecious population. Reproductive output increased with vegetative size in both species, and the scaling relationship did not differ between them despite their differing sexual systems. After accounting for size, C. sessiliflora produced more reproductive structures and more connected pups than C. nutans, and we found no evidence of a trade-off between clonal and sexual output in both species. Within C. sessiliflora, staminate individuals produced more flowers than pistillate individuals across comparable sizes. Co-occurring Catopsis can differ markedly in baseline reproductive and clonal output while sharing a conserved scaling of output on vegetative size, offering a foundation for further comparisons of sex-specific reproductive allometry in bromeliads.

Premise Rising temperatures can reduce plant reproductive success by disrupting pollen development, yet little is known about how reproductive heat sensitivity varies among natural populations. We evaluated pollen viability responses to elevated temperature in two closely related taxa of yellow monkeyflowers across multiple geographic scales to determine whether heat sensitivity varies among species, between populations and across elevations. Methods We conducted three common garden growth chamber experiments. First, we compared pollen viability responses to heat stress between Mimulus guttatus and members of the M. tilingii species complex. Second, we tested whether broad elevational categories explained variation in heat responses. Third, we evaluated heat sensitivity among nine eastern Sierra Nevada populations of M. guttatus spanning an elevational gradient. Pollen viability was assessed following exposure to control and heat treatments. Key results Heat exposure reduced pollen viability in all experiments. In the species comparison experiment, pollen viability decreased more strongly in the high-elevation restricted M. tilingii species complex than the widespread M. guttatus. We found substantial population-level variation in pollen viability within M. guttatus but not members of the M. tilingii complex. Broad elevational categories did not explain this variation in pollen viability responses. However, within eastern Sierra Nevada populations, reductions in pollen viability became stronger with increasing source elevation. Several populations deviated from this trend, indicating reproductive responses to heat cannot be explained by elevation alone. Conclusions Pollen heat sensitivity varies substantially among species and populations of yellow monkeyflowers. Elevation alone is insufficient to predict pollen viability responses to elevated temperatures, suggesting that local adaptation or genetic variation may contribute to reproductive heat tolerance. Some populations of M. guttatus may contain greater capacity to maintain reproductive function under future warming, highlighting the importance of considering intraspecific variation when predicting plant responses to climate change.

Hybridization and introgression are thought to play key roles in the formation of biodiversity. However, detecting gene flow between species and understanding reticulation patterns remain challenging, especially in species-rich lineages with complex evolutionary histories. Adiantum is a large fern genus, and ecological studies in Amazonia have found that species identification is often difficult due to morphological similarity and overlapping characteristics among species. Although several hybrids have been described in tropical America, comprehensive studies investigating genetic exchanges in this genus are still lacking. We used chloroplast and nuclear phylogenomic data to examine evolutionary relationships among tropical American Adiantum species. By combining traditional phylogenetic analyses with advanced bioinformatic methods such as HybSeq-based target capture, reference-guided phasing (HybPhaser), and network-based analyses, we found widespread reticulate evolution involving both recent and ancient hybridization events. These were especially common among those species that have been difficult to delineate morphologically. Our findings indicate that reticulate evolution has played an important role in shaping the diversity of neotropical Adiantum, especially within the tetraphyllum lineage. Such widespread hybridization has no doubt contributed to morphological ambiguity and taxonomic challenges. Our integrated analytical approach provides a first attempt at untangling the reticulate evolutionary history in this group, and future studies with additional sampling can be expected to clarify the evolutionary processes further.

Background and Aims Epiphytes comprise approximately 10% of global vascular plant diversity and play key roles in many tropical ecosystems. They possess traits allowing survival under limited water availability (i.e. the epiphytic trait syndrome), but knowledge of these trait combinations is taxonomically biased and their generality remains unclear. The megadiverse genus Anthurium (Araceae), with ~600 epiphytic species, offers an opportunity to address this gap by examining patterns of leaf trait covariation, their phylogenetic context, and differences among life forms. Methods A common garden experiment was conducted using 40 species from 13 sections spanning a gradient of epiphytic incidence. Twenty-one anatomical, morphological, and physiological leaf traits were quantified. Patterns of trait variation were assessed, and associations between leaf traits and epiphytism were evaluated both with and without accounting for phylogenetic relationships. Key Results Leaf trait variation was captured by two principal components. The first axis was negatively associated with stomatal density and size, leaf thickness, and leaf water content, while the second axis described a trade-off between leaf mass per area (LMA) and water loss rate. Epiphytic species generally exhibited smaller, more numerous stomata and higher LMA, consistent with adaptations for water retention. Epiphytism showed a phylogenetic signal; however, trait covariation patterns were not influenced by phylogenetic relatedness. Conclusions We found consistent associations between epiphytism and several water-related leaf traits in Anthurium, but some of these associations departed from general expectations of an epiphytic trait syndrome. Water-related traits showed variable phylogenetic signal and reflected multiple functional strategies for coping with intermittent water supply. These findings highlight the diversity of functional strategies underlying epiphytism and expand current understanding beyond well-studied taxa.

Premise of the studyDisentangling ancestry of insular plant lineages is important for resolving their evolutionary histories but often complicated by polyploidy, an overrepresented condition in remote island floras. A phylogenomic approach was used to study the origin of subgenomes of the tetraploid Hawaiian silversword alliance and advance understanding of this major example of adaptive radiation. MethodsSequences from 461 target-capture nuclear loci were phased to subgenomes of the tetraploid silversword alliance (Compositae) using assemblies from diploid North American tarweeds as clade references. Maximum-likelihood and multispecies- coalescent analyses of phased loci were conducted with and without representatives of diploid lineages throughout tribe Madieae. Key resultsAn allopolyploid origin of the silversword alliance was corroborated, with Subgenome-A phased consistently to Anisocarpus madioides and Subgenome-B phased to diploid representatives of each of three other sublineages of the "Madia" lineage. Phylogenomic analyses indicate Anisocarpus madioides is more closely related to Subgenome-A than to other tarweeds, including Anisocarpus scabridus. Subgenome trees for the silversword alliance are highly congruent with each other and with structural genomic differences between lineages. ConclusionsThese results indicate an even closer relationship of the silversword alliance to extant California tarweeds than previously understood. Anisocarpus madioides has chromosomal and ecological traits anticipated in an ancestor of the silversword alliance, with the widest geographic range among perennial tarweeds and sticky bracts completely enveloping fruits. Within the silversword alliance, robust support for four major clades reinforces the phylogenetic value of chromosomal interchanges and taxonomic insights by Asa Gray regarding the enigmatic liana Dubautia latifolia.

Hybridization is a powerful process in plant evolution generating reticulate patterns of speciation, introgression, and chloroplast capture. In the Petota clade of Solanum, which spans cultivated and wild potatoes, these processes cause much of the taxonomic complexity of the group. We examined the evolutionary history of the Commersoniana group (Solanum commersonii and S. malmeanum) relative to S. chacoense (Tuberosa Group) using an integrative framework of phylogenomics and morphology. With target-capture sequencing (Angiosperms353) of nuclear and plastid loci recovered from herbarium specimens, together with data mining we built nuclear and plastome phylogenies and ran symmetry tests, gene concordance analyses, and coalescent simulations to weigh incomplete lineage sorting against chloroplast capture. The data reveal cytonuclear discordance and events consistent with chloroplast capture from S. chacoense into Commersoniana lineages supported by both empirical and simulated results. Phylogenetic networks confirm repeated historical and recent reticulation, especially involving S. malmeanum. Non-metric Multidimensional Scaling (NMDS) of morphological traits did not recover clear species boundaries but was consistent with a hybrid origin for the group. These results indicate that recurrent hybridization and event consistent with chloroplast capture are strongly influencing evolution in the examined wild potatoes, complicating classical taxonomy and informing conservation and breeding. They also underscore the value of combining genomic and phenotypic data to resolve species boundaries in plant groups with tangled hybrid histories.

Premise of the study. Phenotypic plasticity is advantageous for many plants that experience environmental fluctuations, but strong selection pressures can establish limits to plasticity. In deciduous trees, the ability to time leaf elongation in response to spring temperatures can extend the length of the growing season for a given year's climate. However, emergence timing may have undergone strong selection by factors like cold temperatures, limiting the capacity of locally adapted populations to adjust via plasticity to new conditions. Methods. Using a nine-year dataset of 659 families of Quercus lobata in two common gardens, we tested how climate of origin and annual temperatures at the gardens affected variation in phenology. We then examined whether leaf emergence timing was under selection in the gardens by testing its effects on growth. Finally, we tested whether among-year plasticity in leaf emergence timing conferred a growth benefit. Key results. Year-to-year environmental variation explained more phenological variation than genetic differences associated with climate of origin, yet trees from cooler climates were more constrained in their ability to track temperature than trees from warmer climates. We found evidence of weak stabilizing and directional selection on phenology, suggesting that strong selection in favor of earlier phenology is unlikely. Finally, we found no evidence that selection has favored increased plasticity in Q. lobata. Conclusions. Phenological plasticity remains a key driver of plants' response to changing temperatures, but it is constrained by natural selection. As temperatures rise, these processes may disproportionately limit the ability of trees adapted to cooler climates to shift their phenology to match spring temperatures.

Extrafloral nectaries (EFNs) are a widespread plant defense mutualism trait and are highly convergent, appearing in hundreds of plant lineages worldwide. Here we investigate a report of possible EFNs in Erythranthe angulosa, a recently-described California wildflower. We integrate field observations, insect bioassays, an induction experiment, and microscopy to test for signatures of EFN function, finding no evidence that the distinctive axillary swellings produced by E. angulosa function as EFNs. We also uncovered two distinct morphs at the type locality of E. angulosa that diverge in the number of axillary swellings produced, as well as other shoot architecture traits such as stem thickness, leaf size, and branch number. Although the axillary swellings appear to not function as EFNs, they remain a compelling morphological variant within the yellow monkeyflowers that may perform storage or another unknown function.

Myricaria Desv. (Tamaricaceae) is a genus of shrubs that play a keystone role in montane riparian ecosystems across Eurasia, shaping riverine habitats and supporting ecological function. The genus has a centre of origin in the Qinghai-Tibetan Plateau and exhibits a broad distribution, but many species boundaries are unresolved. Here, we present the first phylogenomic analysis of Myricaria using the Angiosperms353 target enrichment bait set, with sampling across its full geographic range. Off-target plastid loci were extracted from next-generation sequencing data using the CAPTUS bioinformatics pipeline. We infer species relationships using ASTRAL-IV and network analysis with SplitsTree, in conjunction with morphology. We also provide a taxonomic treatment of the genus, integrating our morphological observations and phylogenomic analyses for species delimitations. Based on our analyses, recognise two infrageneric sections: sect. Parallelantherae (containing only M. elegans) and sect. Myricaria (the remainder of the genus, with type species M. germanica). We also propose synonymising M. davurica, M. bracteata and M. squamosa with M. germanica. Although species boundaries in the Asian highlands remain unresolved, we conclude that the species M. elegans, M. germanica, M. laxiflora, M. longifolia, M. platyphylla, and M. pulcherrima are well-supported both phylogenomically and morphologically.

Self-fertilization results in reduction of heterozygosity over time, accelerated by small population sizes, restricted ranges, and fragmented habitats. Yet some species maintain heterozygosity despite these factors. One is Corallorhiza bentleyi, a threatened, mycoheterotrophic, self-pollinating orchid restricted to Virginia and West Virginia, USA. Reduced representation sequencing was employed across five of the ~12 known localities of C. bentleyi, including representatives of sister species C. involuta from Mexico, to quantify patterns of population structure and genomic diversity. Surveys of C. bentleyi revealed a predominance of the cleistogamous (closed-flowered) growth form. Differentiation was observed between the two species but with weak population structure in C. bentleyi. Surprisingly, excess heterozygosity and negative inbreeding were recovered in both species, counter to expectations. Analyses provided evidence against bioinformatic artifacts (collapsed paralogs), small-sample bias (Robertson effect), and accumulation of mutations along chromosomes due to low recombination associated with selfing (Meselson effect) as explanations for excess heterozygosity. Demographic analyses favored a model of post-glacial divergence among C. bentleyi and C. involuta lacking bottlenecks. Finally, simulations under alternative selection scenarios favored models of overdominance vs. those of negative frequency dependent selection. It was concluded that overdominance, namely selection against selfed homozygotes, is the most likely explanation for elevated heterozygosity in C. bentleyi. Conservation concerns are discussed in light of these findings and the threats of extinction for one of the most vulnerable orchid species in North America.

The Himalayan-Tibetan-Hengduan (HTH) region is the richest biodiversity hotspot for high-elevation plants. However, owing to its remote and physically challenging topography as well as the trans-national nature of the region, many taxonomic problems in the area remain unresolved, particularly in the Himalaya. This, in turn, has impeded our understanding of the assembly of its extraordinary high-elevation flora. Here, we resolve phylogenetic relationships and delimit species in a distinctive clade of honeysuckles that is endemic to the HTH, the Isoxylosteum clade of Lonicera, using restriction-site associated DNA sequencing (RADseq) and morphological data. Five species complexes of Isoxylosteum have standardly been recognized. Three of these complexes are highly variable and have been divided into several varieties or species each. Phylogenetic, population structure, and morphological analyses of leaf and floral traits from samples collected across the range of the clade support the recognition of five species, including a species that has most often been recognized as a variety of L. rupicola (L. rupicola var. minuta). Instead, we find that it is sister to L. spinosa. This is surprising because the geographic range of L. minuta is contiguous with the other varieties of L. rupicola in the northern Hengduan region but widely separated from L. spinosa whose range lies mainly to the west of the Tibetan plateau. On close examination we find that several morphological and ecological traits also support a closer relation of L. minuta to L. spinosa. None of the other eight previously recognized varieties and species were supported. Floral traits showed high discriminatory power, correctly classifying 89% of samples to species. By comparison, leaf dimensions classified species with 59% accuracy. Our results identify diagnostic morphological apomorphies for each recognized species and major clade and provide a revised taxonomic framework for Isoxylosteum.

Balancing sexual reproduction with vegetative growth poses challenges for many plants. Additionally, reproductive effort, such as production of pollen or flowers, is not always correlated with numbers of viable and germinable seeds. Energetic tradeoffs like these can be particularly fraught for imperiled species and might be especially complicated in landscapes with a possibility of interspecific hybridization. In this multi-year study, we track the reproductive effort, flowering phenology, and reproductive output of two interfertile Sarracenia (pitcher plants). We show that reproductive effort varies among years and sites, and that production of pollen and flowers does not always result in higher seed output. We demonstrate that phenological overlap in the timing of flower production and pollen viability could enable hybridization, and that the more imperiled taxon produces fewer seeds per flower. Results have implications for conservation of these pitcher plants, management of hybridization in these and other systems, and general principles of reproductive allocation.

Root-associated fungal (RAF) communities can influence tree nutrient acquisition and performance, yet their structuring factors and relationship with tree growth remain poorly understood, particularly near environmental treelines. We characterized root-associated fungal (RAF) communities on fine roots of white spruce (Picea glauca [Moench] Voss) in paired forest and treeline plots across two elevational and one moisture-limited treeline ecotones in Alaska. Using ITS2 DNA metabarcoding of fine root tips, we characterized individual RAF community alpha and beta diversity and tree growth based on basal area increment (BAI) over 5-30 years. As a result, sampling site was the strongest predictor of RAF composition, explaining 19.6% of variation, while soil pH explained an additional 11.7%. Treeline effects on RAF communities were weaker and context-dependent, with treeline trees showing distinct community composition in the Alaska Range, lower alpha diversity across all Hill numbers in Interior Alaska, and higher ECM relative abundance in the Brooks Range. RAF composition did not differ between fast- and slow-growing trees within sites. In contrast, alpha diversity was negatively associated with tree growth: OTU richness, Shannon and Inverted Simpson indices significantly predicted BAI over the previous 5, 10 and 15 years, with fast-growing trees supporting less diverse RAF and ECM communities. This relationship was strongest for recent growth and weakened with longer BAI averaging periods. Our results suggest that high growth of mature P. glauca is not necessarily associated with greater RAF or ECM diversity or specific taxa but may instead rely on fewer dominant or functionally effective fungal partners.

In plants, ecological interactions such as pollination depend on whole-plant phenotypes, where coordinated variation among vegetative, floral, and reproductive traits can shape reproductive success. However, empirical studies linking integrated phenotypes that include non-floral traits to reproductive outcomes within populations remain limited. While prior work has shown that crimson monkeyflowers exhibit heritable variation in foliar anthocyanin striping, the functional significance of the trait has been thus far unknown. Using plants derived from natural populations, we conducted field and greenhouse experiments to assess whether foliar striping is genetically correlated with traits related to pollinator attraction. We found that foliar striped plants consistently exhibit larger flowers, greater nectar rewards, and decreased proportions of viable pollen relative to non-striped plants. When we manipulated flowers within plants with and without foliar striping to allow only outcrossing or only self-fertilization in a field environment, we found that outcrossed flowers had higher reproductive success than did self-fertilized, with outcrossed flowers from plants with foliar striping producing the highest overall seed numbers and seed mass. Our results reveal patterns of coordinated foliar and floral trait variation and associated reproductive output that are consistent with a pollination syndrome framework. The link between foliar pigmentation and increased per-calyx reproductive output represents a novel association between foliar pigmentation and a broader evolutionary and ecological function.

Polyploidization can profoundly affect plant metabolite biosynthesis, yet its influence on chemodiversity remains poorly understood, despite the central role of chemodiversity in mediating plant interactions with the environment. The coexistence of facultative apomictic and sexual reproductive systems across ploidy levels in Hypericum provides an excellent model for investigating the evolution of chemodiversity following polyploidization. We analyzed ploidy levels and leaf metabolic fingerprints across selected populations of three Hypericum taxa, H. maculatum, H. perforatum subsp. perforatum and H. perforatum subsp. veronense. Polyploidization was common across all three taxa. Leaf metabolic fingerprints were more pronouncedly differentiated by the ploidy level of the mother plant (F0) than that of the offspring (F1). Although unique metabolic features emerged in plants of most ploidy levels, diploid plants exhibited fewer metabolic features than polyploid plants. Higher Shannon diversity, functional Hill diversity, and intensities of features belonging to specific chemical families were associated with higher F0 ploidy levels in H. perforatum subsp. perforatum, but not in H. maculatum and H. perforatum subsp. veronense. Our findings demonstrate that polyploidization can lead to rapid shifts in chemodiversity across generations in Hypericum. The fast divergence in chemodiversity associated with polyploidization in H. perforatum may contribute to its remarkable invasive potential.

Bulk phloem flow is driven by pressure gradients generated by water drawn from the xylem, coupling source-sink transport with water status. Huanglongbing (HLB), a phloem-affecting bacterial disease of citrus, disrupts phloem transport, and causes canopy water deficit. Although improved water management can enhance HLB-affected tree health, the effects of HLB on water-driven source-sink relations are unknown. Fruits function as both carbon sink and water reservoir, but the role of fruit in regulating whole-tree water status remain poorly understood. We examined leaf-fruit water relations in HLB-affected citrus and evaluated how HLB exposure duration, fruit developmental stage, and source-sink manipulation shape these dynamics. Source-sink relations were manipulated in branches of symptomatic trees with long-term (four years) and recent (six months) HLB exposure. We girdled branches with a single fruit as the sink and defoliated at (0%, 50%, or 75%), and an ungirdled, non-defoliated branch served as control. We measured stomatal conductance, leaf hydraulic traits, leaf and fruit soluble sugars, diurnal fruit shrinkage (to estimate xylem backflow) and fruit water loss. Source-sink manipulation did not affect shoot total soluble sugar. HLB-exposure resulted in less negative osmotic potential, more negative turgor potential and reduced modulus of elasticity and relative water content at turgor loss point. HLB exposure also increased diurnal fruit shrinkage, with shrinkage responses to source-sink manipulation varying across fruit development stages. Collectively, these findings suggest that long-term HLB exposure promotes leaf acclimation to water deficits, however, high sink demand may diminish the leaf water status regulation at Stage II, when fruit sink carbon demand is highest.

Sinia rhodoleuca, the sole species of the monotypic genus Sinia (Ochnaceae), was previously transferred to Sauvagesia based mainly on morphological similarities. However, its phylogenetic position has remained unresolved because molecular data for the species were unavailable. Here, we generated genomic data for Sinia rhodoleuca and reconstructed its phylogenetic position within Sauvagesieae. Our phylogenomic analyses consistently recovered Sinia rhodoleuca as sister to Indosinia, whereas the Neotropical Sauvagesia formed a distantly related lineage, rendering Sauvagesia broadly circumscribed non-monophyletic. Comparative morphological evidence further supports the close relationship between Sinia and Indosinia, particularly in their closely parallel secondary veins, lacerate stipules, and prominent petaloid staminodes, while differences in floral characters support their recognition as distinct genera. We therefore reinstate Sinia as a distinct genus and provide a revised taxonomic treatment of Sinia rhodoleuca. Our study demonstrates how phylogenomic evidence can resolve long-standing taxonomic uncertainties and reveal evolutionary relationships obscured by morphological similarity.

Reports that the South American climbing vine Boquila trifoliolata modifies its leaf shape to mimic leaves of its host plant have raised considerable attention. Boquila leaf development was proposed to reflect visual inputs perceived in an unknown manner. However, the very existence of Boquila leaf shape mimicry remains inconclusive, since the reported observations are open to alternative explanations. We performed an initial quantitative characterization of leaf shape variability in glasshouse-cultured clonal Boquila plants grown without close host contact, and attempted to reproduce the leaf shape mimicry phenomenon under controlled culture conditions using live olive (Olea europaea) plants, artificial (decoy) olive or artificial ivy plants as supports. While we found leaves of variable shape (including those resembling ivy leaves) both in plants grown without host contact and in those climbing on live or decoy hosts, we did not observe any link between leaf shape and host presence or character. Instead, the leaf shape appears to be affected by environmental conditions including the season. Although our study was limited to a single Boquila genotype and an ecologically unrealistic host selection, our observations suggest that the alleged mimicry might originate from unintentional misinterpretation of intrinsic discontinuous leaf shape plasticity in field observations.

Stump sprouts may originate from pre-existing preventitious buds or adventitious buds, but whether these developmental origins produce distinguishable whole-shoot phenotypes remains unclear. We examined all visible sprouts on a single stump of an ornamental cherry (Prunus sp.) and measured four preselected traits: fresh weight, basal diameter, shoot length, and node number. The initial census comprised 35 sprouts. These traits were strongly correlated and were dominated by a common multivariate growth axis. Unsupervised mixture modelling identified statistical components within the morphological distribution, but these components could not be assigned to preventitious or adventitious developmental origins. During subsequent examination, we identified an unexpected basal longitudinal cavity and recorded its presence and axial length. The cavity occurred in 23 of 31 sectioned sprouts (74%). After complete removal of the initial sprout population, all visible sprouts were collected again seven days later. This second cohort comprised 22 substantially smaller sprouts but reproduced the coordinated whole-shoot growth structure. Remarkably, the basal longitudinal cavity occurred in 16 of 22 sprouts (73%), nearly identical to its initial frequency despite the marked difference in shoot size. Cavity presence was largely independent of overall shoot size, whereas cavity length increased with size among cavity-positive sprouts. Thus, gross quantitative morphology did not discriminate the hypothesized developmental origins, whereas basal anatomy revealed a reproducible feature potentially informative of developmental history. Direct anatomical and ontogenetic analyses are required to determine whether the basal longitudinal cavity is associated with sprout origin.

Background and AimsDistylous 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. MethodsWe 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 ResultsOur 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. ConclusionsIn 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.