Annals of Botany

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.

1. Most plant species are genetically differentiated among populations, often reflected by phenotypic trait variation that corresponds to local adaptation. Yet the strength of local adaptation and heritable contribution to phenotypic traits vary across traits, species, and environments. Additionally, climate change is rapidly altering environmental conditions, and the climate may shift faster than populations can adapt or track the change via dispersal, resulting in adaptive lags. However, it remains unclear how widespread such adaptive lags are across plant species. 2. We focused on Hordeum murinum, an annual ruderal grass widespread in Europe. We combined continental-scale in situ measurements of 2070 plants across 207 populations with common garden experiments across two contrasting climates and two soil types to disentangle heritable variation from phenotypic plasticity and assess potential adaptive lags under climate change. 3. We found that heritable variation was pronounced in developmental traits, particularly flowering time and plant height, while seed weight, reproductive investment and SLA showed intermediate heritable contribution, and flag leaf area and total biomass were primarily plastic. Heritable trait variation was strongly associated with temperature at the populations origin, and trait clines were consistent with in situ patterns, suggesting that temperature is the main driver of genetic differentiation in H. murinum. However, we detected that fitness peaked in populations originating from warmer climates, indicating that evolutionary responses may not keep pace with rapid environmental shifts. 4. Synthesis: Our results highlight that H. murinum harbors substantial heritable variation, shaped primarily by temperature. However, the pace of evolutionary change may be insufficient to track ongoing climate change, leaving populations potentially vulnerable to future environmental conditions.

1. Stomata and leaf traits are key regulators of plant water use efficiency and are expected to have changed in response to rising atmospheric CO2 concentrations and climate warming over the past centuries. However, long-term data documenting such changes are rare. 2. We leveraged herbarium collections to track changes in stomatal characteristics and leaf traits in 656 individuals of invasive Japanese knotweed and its hybrid Bohemian knotweed collected across their European range and spanning 160 years of invasive spread. 3. We found that several functional traits including stomatal density and maximum anatomical stomatal conductance did not show significant changes over time but that plants adjusted their stomatal size and shape over time, and that these changes were associated with increased atmospheric CO2 levels. Interestingly, Reynoutria japonica showed increases in stomatal size and stomatal elongation, while the hybrid R. x bohemica showed a reduction in stomatal size. Traits also varied systematically with climates of origin. Plants from warmer origins with higher evaporative demands during the growing season had thicker leaves, lower SLA, smaller stomata and higher stomatal density, indicating more conservative water-use strategies. Stomatal density and gas exchange capacity co-varied with leaf structural traits, and there was a trade-off between stomatal size and number. Overall, fast leaf economic traits were associated with slow physiological traits. 4. Our results suggest that stomatal anatomical plasticity may enhance climate resilience by maintaining a stable maximum gas exchange capacity across environmental gradients. Herbarium collections provide a unique resource for reconstructing plant responses to historical environmental changes and understanding intraspecific trait variation.

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.

The tribe Spermacoceae (Rubiaceae) comprises a morphologically diverse assemblage of approximately 1,400 species distributed across the Neotropics, Africa, Asia, Australia, and Pacific region. It remains one of the most taxonomically intractable groups in the family, with generic limits repeatedly redefined for more than two centuries. Previous phylogenetic studies based on a limited number of plastid and nuclear markers left numerous relationships unresolved and provided sparse representation of Neotropical lineages. Here, we present the first phylogenomic study of the tribe based on plastome-scale data and expanded sampling of Neotropical taxa. We sampled 121 species representing 55 genera spanning all major clades and generated 123 new plastomes, including 25 species incorporated into a molecular phylogenetic framework for the first time. Maximum-likelihood and Bayesian analyses recovered a highly resolved and strongly supported phylogeny, with uncertainty restricted to a small number of deep backbone nodes. Pollen and seed micromorphology provided additional evidence for evaluating phylogenetic relationships. The resulting phylogenetic framework clarifies generic boundaries across several problematic lineages and supports multiple taxonomic changes. Pervasive homoplasy in seed and floral characters rendered several traditionally recognized genera non-monophyletic, warranting new combinations, including Edrastima oxycoccoides, Stenotis alexanderae, and S. prostrata, and a reassessment of taxa such as Terrellianthus serpyllaceus and Oldenlandia dusenii. We further identify genera requiring additional study and provide an updated key to the 82 recognized genera of Spermacoceae. Together, these results provide the most robust phylogenetic framework yet available for the tribe and establish a foundation for future systematic, biogeographic, and evolutionary research.

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.

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.

Yeasts thriving in floral nectar have a proven ecological engineering capacity, as they modify the internal environment and the rewards of individual flowers in ways that influence how plants and pollinators interact. This floricentric perpective, however, produces only a partial view of the potential role of yeasts in plant-pollinator interactions, and little is known on their possible engineering effects on whole inflorescences. This study assessed yeast ability to shape features of the vertical inflorescences of Gladiolus illyricus (Iridaceae), a Darwins syndrome plant (acropetalous protandrous flowers pollinated by insects foraging from bottom to top). When yeasts were excluded from inflorescences a declining gradient in nectar sugar concentration built up from the oldest, female-stage flowers at bottom up to the youngest, male-stage ones at top. This plant-intrinsic gradient was reversed in inflorescences with yeasts, where sugar concentration increased from the female-stage flowers harboring dense yeasts population to male-stage ones with few yeasts. The two species of yeasts involved (Metschnikowi reukaufii and M. gruessii) differed in their effects. Results add support to the growing consensus that specialized nectar yeasts can obfuscate intrinsic patterns of intra and interspecific variation in flowering features of plants at the level of individual flower, inflorescence, population and plant community.

Background and AimsThe development of unisexual flowers relies on the tight coordination of flower organ identity and sex determination. The genus Quercus is typically considered strictly monoecious, bearing fully segregated male and female flowers within the same individual tree. However, several reports of atypical flowering across the genus challenge this canonical view, suggesting that flowering in oaks may be more flexible than traditionally assumed. In this work, the dynamics of flower development in Quercus orocantabrica were examined to correlate contrasting floral morphologies with divergent molecular profiles. MethodsThe flowering phenology of Q. orocantabrica trees was closely monitored over several individuals and years, together with a detailed floral morphological analysis of male, female and atypical flowers. Key floral homeotic gene homologues were identified, and their expression assayed in the development of different flowers. Key ResultsRecurrent and widespread hermaphroditic flowering was detected in several Q. orocantabrica trees, frequently associated with unseasonal flowering events. Gene expression analysis of male, female and hermaphroditic flowers revealed a sex-biased expression of Q. orocantabrica B- and C-class genes, with the B-class gene QoPI in particular being tightly associated with the presence of fully-developed stamens. In addition, the expression of the C-class gene QoSHP contrasted with reports in other Fagaceae, highlighting a potential functional divergence of the C/D-class lineage within the family. ConclusionsThe results here depicted indicate that the dynamics of floral sex identity in oaks are more plastic than traditionally assumed, supporting a reinterpretation of oak reproductive biology based on a versatile and resilient framework responsive to different developmental contexts.

We tested whether seasonal plasticity in photosystem II (PSII) heat tolerance aligns with leaf phenology in tropical trees, comparing evergreen and deciduous species across the wettopostwet transition in a seasonally dry tropical forest of the central Western Ghats, India. This transition, preceding droughtinduced senescence, represents the key window to assess true unstressed thermal plasticity. PSII thermal traits: damage onset (T5), damage midpoint (T50), and temperature between damage onset to full loss (T95-T5), decline width (DW) were quantified in 27 cooccurring species during the wet (27.5{square}{degrees}C) and postwet (31.6{square}{degrees}C) periods. Contrary to phenologybased predictions, PSII plasticity was not structured by leaf habit or successional status. Both T5 (+1.7{square}{degrees}C) and T50 (+0.9{square}{degrees}C) increased significantly across seasons, but responses were speciesspecific, with evergreen and deciduous trees acclimating similarly. The preventionversusforbearance tradeoff (T5 - DW relationship) remained conserved, though leaf habits diverged under postwet conditions. Thermal safety margins based on T50 were large, but T5 revealed vulnerable latesuccessional evergreens (Saraca asoca, Ficus spp.) and Careya arborea. These results show that PSII thermotolerance regulation operates largely independently of droughtavoidance phenology, indicating species identity and not leaf habit drives plasticity in PSII thermal response in seasonally dry tropical forests.

Background and AimsThe evolution of reproductive isolation between previously interbreeding populations is a fundamental driver of plant speciation. Within Amaryllidaceae, Nothoscordum represents an evolutionarily complex genus, characterized by an unusually high incidence of chromosomal rearrangements. During fieldwork, Nothoscordum montevidense and Nothoscordum bonariense were found growing in sympatry, along with individuals exhibiting intermediate morphological traits, suggesting a putative hybrid origin. To test this hypothesis, we employed an integrative approach to characterize the morphologically intermediate specimens and the two sympatric populations. Materials and methodsTo characterize the putative hybrids we have combined morphological, cytogenetic analyses (chromosome counts, CMA/DAPI banding, and FISH) and flow cytometry-based genome size estimation. Phylogenetic relationships and genomic structure were also investigated through Genotyping-by-Sequencing (GBS), complete chloroplast genome assembly, and comparative repetitive DNA analysis. We also performed species distribution modeling and phenological analyses of the putative parental species. Key ResultsMultiple lines of evidence confirm the hybrid origin of the studied plants. Cytogenetic analyses revealed specimens with 2n = 21 (1C {approx} 33 pg = 32.274 Mbp) and 2n = 25 (1C {approx} 37 pg = 36.186 Mbp), accompanied by meiotic irregularities consistent with interspecific hybridization. Chloroplast genome phylogeny identified N. montevidense (2n = 16, 1C {approx} 25 pg) as the maternal lineage, while GBS data confirmed N. bonariense (2n = 26, 1C {approx} 41 pg) as the paternal contributor and revealed evidence of subsequent backcrossing. Comparative analysis of repetitive DNA showed reduced 35S rDNA diversity in the hybrid, indicative of post-hybridization genomic restructuring. Despite the observed genomic complexity, no clear morphological differentiation was detected among hybrid individuals. Phenological analyses and species distribution models demonstrated broad overlap between parental species. ConclusionsOur findings highlight the role of hybridization in shaping genome architecture in cytogenetically labile plant lineages. Furthermore, our results underscore that morphological similarity can mask profound genomic complexity, reinforcing the value of integrative approaches to understand genera characterized by reticulate evolution and genomic instability.

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.

AO_SCPLOWBSTRACTC_SCPLOWThe breeding systems of most Bromeliaceae have not been tested directly. We characterized the floral biology and breeding systems of two epiphytic, tank-forming bromeliads endemic to the Atlantic Forest of Brazil, Vriesea rafaelii (Tillandsioideae) and Billbergia brasiliensis (Bromelioideae), using controlled self- and cross-pollinations in a greenhouse. Both species were self-compatible. Based on seed-set, the self-compatibility index was 0.59 in V. rafaelii and 0.87 in B. brasiliensis. In B. brasiliensis, selfed flowers produced lighter fruits and lighter seeds than outcrossed flowers, whereas in V. rafaelii fruit and seed mass did not differ between self- and cross-pollinated flowers. A subset of V. rafaelii flowers showed a spatial separation of the anthers and stigma (herkogamy) that prevented autonomous selfing. These results add two species to the small set of bromeliads with experimentally characterized breeding systems and highlight differences in reproductive output with selfing.

Flower color has primarily been studied in the context of pollinator attraction, although effects on thermal energy balance are also important, especially in the context of global climate change. We used infrared imaging to compare petal temperatures of white versus pigmented cultivars of ten angiosperm taxa under controlled environmental conditions. Excised sets of flowers (n= 6 sets per species) exhibiting white, light, and/or dark anthocyanin (red to purple) coloration were mounted perpendicularly to the sun at mid-day, under clear sky, low wind (<1 m s-1) conditions. Sunlight was filtered through either UV-transparent or UV-opaque film, and petal temperatures were measured using an infrared camera after one minute equilibration. In all species, pigmented flowers were significantly warmer than lighter-colored conspecifics. Mean differences averaged +5.3{degrees}C for darker-colored versus white morphs, +2.9{degrees}C for lighter-colored versus white. Most warming was associated with visible wavelengths, but additional warming under UV-inclusion was also observed in some species. In situ observations of intact landscape plants under low-wind, high-light conditions corroborated experimental results, with differences exceeding 10{degrees}C observed in some taxa. Temperature differences >7{degrees}C were also recorded for purple versus white sections of the same flower in multicolored Viola and Petunia cultivars. Follow-up experiments using dark-pink and white varieties of Impatiens x hybrida corroborated well-known effects of sunlight intensity and wind speed on floral temperatures, helping to explain inconsistent reports in the literature. Our results clearly demonstrate that anthocyanin pigments can have significant and dramatic impacts on floral temperatures, which could be an important factor driving evolution of flower color. In the context of climate change, floral pigments could amplify the effects of rising global temperatures, negatively impacting plant reproduction and crop yields, especially on the warmer end of species ranges. Changes in flower color could also potentially induce shifts in pollinator communities, which could have community-scale effects.

Pollination and seed dispersal by animals are key drivers of terrestrial biodiversity and ecosystem functioning. Effective mutualistic interactions rely heavily on temporal and functional- trait matching between plants and animals. While global warming is known to induce shifts in plant traits, the extent and direction in which higher temperatures may systematically alter flower and fruit traits across species in natural habitats remains poorly understood. Using elevation as a proxy for temperature across natural populations, we conducted a meta-analysis evaluating 21 quantitative functional traits (15 floral, 6 fruit) across 82 studies and 161 species. Standardized mixed-effects linear regression models revealed widespread, systemic responses to elevational temperature gradients in both reproductive structures. In flowers, higher temperatures were systematically associated with changes in petal and sepal width and length (and hence morphology), longevity, nectar volume, number of flowers, and inflorescence length. In fruits, elevation was associated with changes in vitamin C content, crop size, weight and width. Taken together, these results demonstrate that warming temperatures exert widespread, multi-axis effects on the morphology, availability, timing, and nutritional quality of both flowers and fleshy fruits. Given that flower and fruit traits are developmentally linked and co-determine animal visitor dynamics, these temperature-driven phenotypic shifts are likely to propagate cascading disruptions throughout plant-pollinator and plant-frugivore interaction networks under continued climate change.

PremisePinguicula are carnivorous plants occupying a wide range of habitats, from wetlands to barren rock cliffs, where CAM photosynthesis was recently discovered in several species. This ecological and physiological diversity makes the genus a promising system for exploring the environmental drivers and evolutionary transitions underlying variation in CAM. Here, we present a physiological survey of CAM with a particular focus on the Mexican Clade, which contains the recently identified CAM species. MethodsWe conducted a carbon isotope survey of live and herbarium specimens to identify candidate CAM species. We then measured diurnal gas-exchange patterns and changes in leaf titratable acidity to quantify CAM activity. ResultsPinguicula species exhibited a variety of photosynthetic phenotypes. Pinguicula vulgaris showed no detectable evidence of CAM, whereas P. cyclosecta and P. moranensis demonstrated a C3-CAM physiology with most net assimilation via C3. Pinguicula martinezii also showed the same C3-CAM physiology under well-watered conditions but had strong facultative induction of CAM with drought. Pinguicula agnata displayed net assimilation via CAM. Titratable acidity had a positive correlation with {delta}13C within the species we sampled. ConclusionsOur results support the existence of a CAM physiological continuum within Pinguicula. Notably, closely related species encompass physiologies that span the large variation of CAM. This diversity provides a rare opportunity for future studies to investigate the evolution of CAM in closely related species, including differences and similarities between differing states across the continuum.

Grasslands are vulnerable to increasing drought with global warming, but process-based models lack the mechanistic knowledge required to predict the magnitude of drought impacts. While a plant hydraulics framework has been successful in advancing process understanding of drought responses in trees, and how drought responses vary across rainfall gradients, similar approaches have rarely been applied to grasses. Here, we quantified the progression of key drought response processes in sixteen dominant perennial grasses (seven C3 and nine C4) with differing climatic origins across eastern Australia. We found that stomatal closure, hydraulic impairment and leaf browning occurred concurrently, in contrast to the progressive sequence typically observed in trees. We also found that drought response traits were not correlated with species climate of origin. The early impairment of leaf hydraulic conductance and leaf browning along with the lack of correlation with climate of origin suggest that grasses may employ fundamentally different strategies to adapt to low water availability than trees. These results highlight the need for grass-specific parameterization of drought responses in process-based models.

Fleshy fruits have evolved diverse traits to attract seed dispersers in response to frugivore behavior and sensory capacities. Fruit scent has been suggested to signal ripeness and nutritional quality, yet the volatile components involved and the information they convey remain poorly understood. It is unknown which information is encoded in fruit scent, whether plants actively synthesize these signals, and thus whether scent constitutes an evolved communication system shaping seed-dispersal interactions. Aliphatic esters, chemicals whose odor is often described as fruity, are abundant in some ripe fruits, especially those dispersed by animals which tend to rely on their sense of smell for fruit selection. Moreover, they have been argued to be associated with sugar content, potentially rendering them an honest signal and hence a hotspot of animal-plant chemical communication. We investigated whether aliphatic esters indicate fruit quality honestly and represent an adaptive trait shaped by disperser identity. Using 13 fig species (Ficus spp.; Moraceae) in Madagascar, we quantified seed dispersal by multiple animals using a quantitative ecological network. We then quantified chemical signals and nutritional rewards using thermal desorption gas chromatography-mass spectrometry (TD-GCMS) and high-performance liquid chromatography (HPLC), and used genome-guided transcriptome assembly to identify the candidate genes responsible for ester signaling. Our results show that (a) aliphatic esters occur more frequently in species dispersed primarily by olfactory-oriented mammals than in those dispersed by visually oriented birds; (b) ester abundance correlates positively with soluble sugar across species only in mammal-dispersed species, indicating an honest signal that is activated only when ecologically relevant; and (c) putative AAT gene revealing elevated expression associated with the increased abundance of aliphatic esters, sugars in single mammal-dispersed taxon. Together, these findings support the hypothesis that fruits have evolved to utilize the biochemical link between esters (signals) and sugars (rewards) to provide honest signals to seed dispersers.

O_LIHybridisation is frequently associated with plant invasions; however, its consequences for genome organisation and chromosome evolution remain poorly understood in invasive species. We investigated the extent of hybridisation in the invasive Carpobrotus edulis--acinaciformis hybrid complex and determined the cytogenomic contribution of parental species in hybrid accessions. C_LIO_LIWe combined whole-genome sequencing, population genomic analyses, genome size estimation, repeatome characterisation, chromosome counting and fluorescence in situ hybridisation to compare parental species and hybrid accessions from South Africa and the Mediterranean Basin. C_LIO_LIPopulation genomic analyses revealed widespread hybridisation and introgression, with most invasive accessions showing admixed ancestries. Pattersons D-statistic supported asymmetric allele sharing towards C. edulis. Hybrid accessions displayed genome sizes indistinguishable from C. edulis, whereas C. acinaciformis possessed significantly larger genomes. Repeatome analyses identified marked differences in repetitive DNA composition, particularly in satellite DNA abundance and chromosomal distribution. A newly identified satellite repeat (CarpoSat) showed contrasting chromosomal patterns between parental species, whereas hybrids resembled C. edulis satellite pattern. C_LIO_LIOur results demonstrate that Carpobrotus hybrid accessions are a swarm of later-generation hybrids and backcrosses showing a strong bias towards C. edulis, indicating asymmetric introgression. These findings highlight the value of integrating cytogenetic and genomic approaches to understand genome evolution in invasive hybrid complexes. C_LI

Assessing intraspecific variation in thermal stress tolerance is key to predicting plant responses and long-term persistence under climate change, yet its underlying sources and temporal dynamics remain poorly understood. Using a common garden experiment with four ecologically-relevant temperatures, we evaluated the sources and temporal dynamics of variation in temperature stress tolerance of 18 Lemna minor clonal lines from contrasting climates. Our results showed that past adaptation, physiological acclimation, and within-line variation jointly contributed to variation in performance. The study provides the first evidence of adaptive genetic differentiation in heat stress tolerance in this ecologically-widespread freshwater species, with lines from warmer regions showing higher growth under heat stress. However, these differences were transient and diminished under prolonged exposure. Experimental lines also showed acclimation over time, but these responses were strongly temperature-dependent and occurred only under sub-optimal conditions. Additionally, replicates from some lines exhibited divergent performance trajectories under sustained heat stress, suggesting the emergence of novel phenotypic variation, potentially mediated by epigenetic mechanisms. These results show that heat stress tolerance in L. minor arises from multiple interacting sources and is dynamically shaped by both selective history and immediate exposure time, suggesting a more nuanced, multi-layer understanding of variation in heat stress tolerance.