AoB PLANTS

O_LIRationale: Plants in urban environments often experience heat stress and responses to heat stress often include vegetative and reproductive traits like rosette width and fruit morphology. However, our understanding of natural variation in vegetative and reproductive traits in urban environments is severely limited. C_LIO_LIMethods: We grew an urban weed, Capsella bursa-pastoris, in common garden environments that simulate an urban heat gradient to determine how heat affected growth, survival and reproduction. Additionally, we used geometric morphometric techniques alongside deterministic techniques to quantify variation in C. bursa-pastoris fruit shape and investigated the predictive relationship between fruit shape and seed production. C_LIO_LIKey results: We found that temperatures above 30C act as an environmental constraint on both C. bursa-pastoris fruit shape and reproduction, resulting in malformed fruits and no seed production. However, leaf number and plant survival were unaffected by high urban heat. C_LIO_LIMain conclusions: While plants may grow and survive in the high urban heat, heat could still limit population persistence. C_LI

Gene flow to marginal populations at a species range edge can facilitate rapid adaptation by increasing genetic diversity, reducing inbreeding depression, and introducing novel alleles. In highly inbred populations, hybrid vigor is often observed in the first generation (F1), but hybrid breakdown may diminish fitness in subsequent generations. Thus, benefits of gene flow may be overestimated when only F1 performance is assessed. We tested whether gene flow among populations of the annual plant Erythranthe laciniata (A. Gray) G.L. Nesom, from similar and contrasting environments, confers persistent fitness advantages across F1 and F2 generations at the high-elevation edge of its range in the California Sierra Nevada. Gene flow was experimentally introduced through pollen transfer between cold-edge populations, between cold edge and central populations, and within local cold edge populations, and compared to self-fertilized offspring, the predominant mating strategy of E. laciniata. For F1 progeny, we measured morphological, phenological, and fitness traits in a common garden located near the cold-climate range limit during 2008-2009, a relatively average year, and for F2 progeny in 2009-2010, a relatively wet year. Although F1 crosses showed no initial performance advantage measured in the previous year, F2 progeny from center-to-edge and edge-to-edge crosses significantly outperformed selfed and locally outcrossed lines in fruit mass, total pedicels, biomass, and height. Our findings demonstrate that gene flow can confer long-term fitness benefits, especially among populations adapted to similar selective pressures, and highlight the potential of assisted gene flow to bolster or rescue peripheral populations facing climate change. SIGNIFICANCE STATEMENTSpecies living at the edges of their geographic ranges often have small, isolated populations with limited genetic diversity, which can restrict their ability to adapt to environmental change. Gene flow from other populations may increase adaptive potential, but its long-term consequences remain uncertain because most studies evaluate only first-generation hybrids. Using experimental crosses in the mountain wildflower Erythranthe laciniata, we show that gene flow can produce stronger fitness benefits in second-generation hybrids than in the first generation at a high-elevation range edge. These results suggest that recombination among populations can generate advantageous genetic combinations that emerge over multiple generations. Our findings highlight the potential for assisted gene flow to enhance adaptation and persistence of range-edge populations under climate change.

The Atacama Desert hosts a unique ecosystem formed by the sand-dwelling Tillandsia landbeckii, which extends over hundreds of square kilometers. This vegetation relies primarily on fog as its main water source; however, aeolian sand also plays a crucial role in the long-term persistence of both the species and the overall plant community. The terrain is sloped and exposed to the prevailing wind direction. Tillandsia forms regular banding patterns oriented orthogonally to these landscape features. In this study, we aim to elucidate the abiotic-biotic interactions between sand properties and vegetation characteristics through a comparative approach. Three populations - Caldera, Oyarbide and Arica -, each spanning several square kilometers in the southern, central, and northern regions of the Chilean Atacama Desert, were selected to compare wind regimes, terrain structure, sand and substrate properties, and vegetation structure in order to identify common principles that maintain vegetation integrity. Data were collected from six climate stations, 1,246 substrate samples, population genomic data from 718 individuals, as well as satellite imagery and digital terrain models. Our findings demonstrate that regional wind systems transport sand from distant source areas, while near the ground, Tillandsia vegetation reduces wind velocity and traps sand, leading to the formation of moderately sorted sandy substrates that are similar across all three populations. Sites lacking or containing dead Tillandsia individuals often differ significantly in substrate characteristics. Genetic analyses indicate that Tillandsia populations exhibit strong spatial structure albeit recruiting high genetic diversity and an excess of heterozygosity, reflecting adaptation to the dynamic environmental conditions. We conclude that sand represents an essential component of this ecosystem, while Tillandsia, as the dominant biotic factor, actively shapes and maintains this distinctive desert environment. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=133 SRC="FIGDIR/small/707457v2_ufig1.gif" ALT="Figure 1"> View larger version (66K): org.highwire.dtl.DTLVardef@1d5a9d3org.highwire.dtl.DTLVardef@8067deorg.highwire.dtl.DTLVardef@23470forg.highwire.dtl.DTLVardef@e2ae1_HPS_FORMAT_FIGEXP M_FIG C_FIG Generated based on own drawings and iterative improvements using ChatGPT while providing own peer-reviewed research contributions as input and baseline information (MAK). Short summaryWe exemplify unimodal regional wind systems facilitating sand transport toward Tillandsiales. Tillandsiales show a low-energy wind system allowing sand accumulation of predominant grain sizes available at each site. Thereby Tillandsia landbeckii modifies and maintains its own microenvironment. Genomic data reveal high clonality and excess of heterozygosity promoting fitness in a hyperarid environment, and abiotic factors drive the selection of diverse and adaptive Tillandsia phenotypes.

BackgroundNon-optimal temperatures have become a major constraint on plant development under rapidly changing climatic conditions. Both sub- and supra-optimal temperatures reduce physiological activity, alter plant morphology, lead to plant mortality, and ultimately decrease crop productivity. Temperature-tolerant plants employ physiological and morphological mechanisms to mitigate such stress. In this study, we aimed to identify the source of temperature tolerance in warm-climate adapted melon (Cucumis melo L.). ResultsSuboptimal temperature-tolerant accession (Ananas Yoqneam; AY) and susceptible accession (PI414723) were reciprocally grafted and grown under controlled temperature regimes of 16 {degrees}C, 25 {degrees}C, and 35 {degrees}C. Physiological and morphological traits were measured to characterize tolerance mechanisms and whole-plant responses. Temperature emerged as the dominant factor governing plant performance. Whereas non-grafted parental lines maintained consistent differences across all temperature regimes, reciprocal graft combinations diverged mainly under suboptimal (16 {degrees}C) conditions. Under these temperatures, scion identity strongly determined whole-plant performance through biochemical limitations. ConclusionThese results highlight the importance of scion-derived traits in abiotic stress tolerance and their downstream influence on root function.

O_LIClimate change is reshaping agriculture through both gradual shifts and increasingly unpredictable extremes. Plants cope using developmental plasticity and bet-hedging, but it is unclear how these biological strategies align with the ways farmers perceive and respond to climate risks. This study investigates: (1) whether farmers understand climate change as incremental trends or recurrent shocks, (2) how their adaptations parallel plant plasticity and bet-hedging, and (3) under which climate scenarios these adaptations best support yield stability. C_LIO_LIWe combined qualitative research and modelling by conducting fifty semi-structured interviews with farmers, agricultural associations and public administrators across three climatically distinct Italian regions, and by developing an agent-based stochastic simulation that represents farmer-like plasticity (delayed sowing) and bet-hedging (staggered sowing) under drought and flood scenarios. C_LIO_LIFarmers described climate change as both gradual transformation and intensifying volatility. Their adaptive responses - adjusting calendars, switching crops and diversifying production - closely aligned with plant strategies, though articulated in practical rather than scientific terms. Simulation results showed that plasticity enhanced yields under systematic shifts in conditions, whereas bet-hedging reduced losses in highly variable climates characterised by frequent transitions between extremes. C_LIO_LITogether, the qualitative and modelling findings demonstrate that plant and farmer adaptation logics converge in complementary ways. Plasticity supports performance under gradual change, while bet-hedging buffers unpredictability. These insights highlight the potential for co-designed tools that link plant traits, farmer decision-making and ecological risk, strengthening climate-resilient agricultural planning and improving communication between farmers, breeders and plant scientists. C_LI Societal Impact StatementClimate change is transforming agriculture through both gradual shifts and increasingly unpredictable extremes, challenging farmers ability to protect crops and livelihoods. This study brings together farmer experiences and plant adaptation strategies to explore how people and plants respond to similar climate pressures. By showing that farmers practices mirror plant plasticity and bet-hedging, our findings highlight opportunities to design climate-resilient agriculture that aligns biological traits with real-world decision-making. This work can inform plant breeders, extension services and policymakers seeking to support farmers through clearer communication, better risk-management tools and more adaptable crop varieties, ultimately strengthening resilience in food systems.

Abstract summaryThis report presents a preliminary bryoflora for Grand Staircase-Escalante National Monument (GSENM) in southern Utah. The inventory included over 1000 collections made across 40 localities (i.e. macrohabitat types) spanning two ecologically important gradients in bryophyte habitat: shade and moisture availability. At present, the growing checklist contains 117 taxa of liverworts and mosses including 27 families, 65 genera, 116 species, 9 varieties, and 1 subspecies. Noteworthy records include 49 putative taxa new for the state of Utah, and 2 undescribed species in the genera Grimmia and Schistidium. We propose 4 of these species be considered for addition to the recently revised bryoflora of North America. As expected for arid and semiarid environments, the bryophytes of GSENM are predominantly acrocarpous mosses (75%) followed by pleurocarpous mosses (16%), thalloid liverworts (7%), and leafy liverworts (2%). The most diverse families included xeric-soil acrocarpous mosses in the Pottiaceae (35%) and xeric-rock acrocarpous mosses in the Grimmiaceae (15%). Both xeric and mesic species were recovered in the Bryaceae (10% of species) while the pleurocarpous Amblystegiaceae included mesic and hydric species (7%). Most species in the bryoflora have broad global or disjunct distributions, but notably, the known distribution of 17 species appears limited in the United States, or globally, and warrant monitoring in GSENM. Using floristic habitat sampling across 19 macrohabitat types (combinations of 6 topography and 7 vegetation classes), mean site richness was 17.2 {+/-} 9 (SD) and ranged from 4 to 34 species. Six diversity hotspots supported [≥]30 species and were canyons with perennial or ephemeral streams dominated by mixed conifer, hardwood-riparian, riparian, or pinyon-juniper vegetation. High richness is likely supported by greater habitat diversity including xeric, mesic, and hydric conditions on variable substrates (e.g. rock, soil, biocrust, downed wood, seeps, and riparian aquatic/semi-aquatic habitat). Consequently, managing and monitoring diversity under future climate change and land-use alterations will necessitate a habitat-stratified approach that utilizes repeated floristic habitat sampling to document changes in site-level richness and to predict other candidate diversity hotspots on the basis of microhabitat-level diversity, which could be assessed by trained non-bryologists. Collection data are available to the public as georeferenced and photographed observations of half of the bryophyte collections on our iNaturalist.com project, Bryophytes of Grand Staircase Escalante, available for scientific, educational, or outreach activities. Observations are accessible to visitors (via the smartphone app) who wish to know what species have been found along popular trails in GSENM. Landscape-level richness may not reach that of the neighboring Grand Canyon National Park (>155 species), which supports a unique high-elevation bryophyte community sheltered in the mixed conifer and spruce-fir forests of the North Rims Kaibab Plateau. Future collecting by experts will inevitably uncover more species in this ecologically diverse monument important to conserving dryland bryophyte diversity and ecosystem function. This study will serve as a baseline for future research and long-term monitoring related to climate change impacts on dryland bryophytes including biocrust species. O_FIG O_LINKSMALLFIG WIDTH=158 HEIGHT=200 SRC="FIGDIR/small/708354v1_ufig1.gif" ALT="Figure 1"> View larger version (106K): org.highwire.dtl.DTLVardef@c50925org.highwire.dtl.DTLVardef@1db65c3org.highwire.dtl.DTLVardef@f60909org.highwire.dtl.DTLVardef@cb5244_HPS_FORMAT_FIGEXP M_FIG C_FIG Cover photos (by T. A. Clark): View of sandstone canyon wall along the Escalante River Trail taken during a July collection trip in 2015 (top) during which riparian bryophytes were collected by authro, T. A. Clark, (shown in photo) at a sandstone seep (bottom). Bureau of Land Managements National Landscape Conservation System Grant Cooperative Agreement #L14AC00275 issued to P.I. Lloyd R. Stark, UNLV O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=151 SRC="FIGDIR/small/708354v1_ufig2.gif" ALT="Figure 2"> View larger version (88K): org.highwire.dtl.DTLVardef@86109eorg.highwire.dtl.DTLVardef@1ad0efborg.highwire.dtl.DTLVardef@b2c239org.highwire.dtl.DTLVardef@1ed4a4a_HPS_FORMAT_FIGEXP M_FIG C_FIG Copyright 2020 by the authorsAll content contained herein is the property of the authors and all images the property of Theresa A. Clark and should not be used without permission except for education, in which case inclusion of the author/photographers name in citation or superimposed over any image(s) is requested.

O_LIAquatic algae are key primary producers in the Arctic and Antarctic, yet how cold-water species respond to environmental change is poorly understood. The Polar Regions are increasingly exposed to frequent heat waves, leading to declining ice cover, increased light availability, and decreasing salinity in polar waters. We compared three phylogenetically related but geographically distant polar Chlamydomonas species to test how habitat history shapes algal responses to light, salinity, and temperature stress. C_LIO_LIWe assessed the growth, morphology, and photochemistry of psychrophilic Chlamydomonas acclimated to native-like (lower light, higher salinity) and climate-shifted conditions (higher light, lower salinity). Next, we exposed acclimated cultures to a lethal heat shock and observed how acclimation affects algal temperature stress resilience. C_LIO_LIAll three species acclimated to climate-shifted conditions grew rapidly but showed the greatest sensitivity to temperature stress, with rapid loss of viability and photosynthetic efficiency. In contrast, slow-growing cultures acclimated to native-like conditions exhibited significantly greater resilience to temperature stress. C_LIO_LIOur work is the first to directly link light and salinity acclimation with temperature resilience in psychrophilic algae, suggesting that fast-growing polar green algae may be particularly vulnerable to increasingly frequent heat waves, with major implications for primary productivity in polar environments. C_LI

O_LISubmerged macrophytes are central to freshwater ecosystems functioning but are declining globally under multiple anthropogenic stressors. We aimed to identify general patterns in physiological responses and interaction types, and to assess whether a mechanistic understanding of stressor interactions can be developed from published evidence. C_LIO_LIWe systematically reviewed 12,858 records, identified 172 relevant papers, and extracted effect sizes from 124 experiments included in the meta-analysis. C_LIO_LIMost studies examined combinations of nutrient enrichment, shading, toxic trace metals, warming, and emerging contaminants such as PFAS and microplastics, typically under simplified 2 x 2 factorial laboratory designs. Additive effects dominated (50%), while synergistic interactions were relatively infrequent (14%). Antagonistic interactions often reflected dominance of a single stressor or compensatory responses, whereas synergisms were most frequent with metals combined with co-stressors enhancing bioavailability. C_LIO_LIOur synthesis suggests that accumulated stressors cause negative, but not necessarily amplified, responses, although the limited number of experiments testing more than two stressors means synergistic effects may be underestimated. We propose Stuckenia pectinata as a model organism because of its cosmopolitan distribution, experimental tractability, and available genomic resources, and argue that expanding stressor complexity, duration, and taxonomic breadth will strengthen predictions of macrophyte responses and inform freshwater conservation under global change. C_LI

Under climate change, understanding how plants and crops respond to drought is essential for basic research in ecology and evolution, and improving agricultural resilience. One common method of simulating drought in experimental conditions is by applying polyethylene glycol (PEG) to plants. We investigated drought growth responses in Medicago lupulina (black medic) using PEG to simulate drought stress. We grew Medicago lupulina plants inoculated with Sinorhizobium meliloti in Magenta boxes under controlled conditions and randomly assigned them to one of three treatments: a control, PEG applied to the bottom (PEG added to the bottom-watering container of a magenta box), or PEG applied from the top (PEG poured over the growth media). After 60 days, we measured true leaf number, nodule count, and below- and above-ground dry biomass. PEG treatments significantly reduced above-ground growth, including total biomass and leaf number, but unexpectedly increased nodulation. Our results suggest that while PEG effectively simulates drought stress on above-ground growth parameters, it may not accurately simulate drought effects on rhizobial symbiosis. PEG treatments had no effect on below-ground biomass, suggesting that increased nodulation is not a result of increased plant investment in below-ground growth under simulated drought. We hypothesize that PEG, as a persistent liquid that plants do not absorb, created conditions favorable for nodulation. Overall, these results highlight the importance of interpreting PEG-simulated drought experiments with caution when assessing mutualistic interactions.

Quinoa (Chenopodium quinoa Willd.) is a genetically diverse Andean crop valued for its nutrition and adaptability to varied agroclimatic conditions with potential for cultivation in European and Mediterranean, particularly on marginal lands. Low temperatures during early sowing can impair germination, while delayed sowing increases the risk of poor maturation due to unfavorable autumn weather. To assess the adaptation of quinoa to cold stress, we evaluated germination and phenotypic variation in 60 accessions from highland and coastal ecotypes across three sowing dates in South-Western Germany: late winter (S1), early spring (S2), and spring (S3). Cold stress in S1 delayed seedling-emergence and reduced emergence percentages, yet these plants produced the highest average seed yield per plot (64 g) compared to S2 (46 g) and S3 (35 g). Highland accessions showed earlier seedling-emergence and with higher emergence percentages, while coastal types matured earlier and gave higher yields across sowing dates. A complementary laboratory experiment assessed germination under cold (4.4 {degrees}C) and control (18.3 {degrees}C) conditions, using both manual scoring and image analysis via a Mask R Convolutional Neural Network, to track seedling growth. This confirmed the beneficial germination performance of highland accessions under cold stress, with strong agreement between manual and automated scoring. Our findings suggest that quinoa demonstrates resilience to cold stress with highland quinoa exhibiting superior germination traits, and early sowing, despite reduced emergence, can lead to higher yields. We conclude that combining favorable traits such as faster maturity and higher yield of coastal ecotypes with superior germination traits of highland accessions is a promising avenue for breeding improved quinoa varieties for cold climatic regions.

CoverCress is a new winter annual oilseed crop developed from field pennycress within the past 20 years. Field pennycress is commonly considered to be self-pollinated but little basic research has been published and there is some misalignment of conclusions. Our experience working with pennycress plant growth in greenhouse and field conditions over the past 13 years suggests that outcrossing is uncommon. We conducted lab, greenhouse, and field experiments to strengthen the body of work. Pollen viability kinetics analysis showed that longevity of pollen viability is negatively impacted by increasing temperatures and by direct exposure to light. Samples treated at 4C declined to 50% viability in 12 hours while it took just 2.5 hrs at 37C, and 1.6 hrs in full sunlight on a cool early April day. Cross-pollination was absent among greenhouse-grown plants flowering inside an agitated plastic pollen-containment covering. Across greenhouse tests, high rates of cross-pollination occurred only in an emasculation treatment that rendered flowers male sterile and opened the pistil to cross-fertilization. Field trials designed to measure pollen flow distance using a trackable fae1 knockout reporter gene failed to show detectable movement of pollen under field conditions in two locations. This data strongly suggests that domesticated field pennycress may be considered a self-pollinated crop and managed as such.

Published studies have reported species-variance between profiles of Calvin-Benson cycle (CBC) intermediates, not only between C4 species and C3 species, but also within C3 species (Arrivault et al., 2019, Borghi et al. 2019). It was proposed that this variance reflects lineage-dependent changes in the balance between different reactions, or poising, of the CBC. These earlier studies investigated phylogenetically-unrelated C3 species. In the current study, CBC intermediates were profiled in five closely-related species from Solanum sect. lycopersicon subsect. Lycopersicum. The levels of individual CBC intermediates showed many significant differences. In a principal component analysis, whilst three species (Solanum lycopersicum, Solanum cheesmaniae, Solanum neorickii) overlapped, Solanum pimpinellifolium and especially Solanum pennellii grouped separately, and were at opposing ends of the distribution. When combined with published data, whilst the separation between Solanum species was retained, they formed a group that was separated from five other C3 species, as well as two C4 species. It is discussed that the observed variation in CBC metabolites profiles within Solanum, together with their separation from other C3 species, supports the idea that CBC evolution is shaped both by phylogenetic relatedness and lineage-specific adaptation. HighlightVariance of intermediate levels points to poising of the Calvin-Benson cycle varying between closely-related species in the tomato clade Solanum sect. lycopersicon subsect. Lycopersicum

Residual water losses after stomatal closure have recently been identified as key determinants of drought-induced hydraulic failure, particularly under heatwave conditions. However, little is known about the intraspecific variability of residual conductance (gres) and its thermal sensitivity. Here, we investigated the genetic and environmental sources of variation in gres and its associated thermal parameters (phase transition temperature T_, and temperature sensitivities Q10a and Q10b) in Abies alba Mill., together with vulnerability to xylem embolism (P50). Measurements were performed using the Drought-Box on seven French provenances grown in a common garden to assess genetic variability, and on trees growing across contrasting forest sites to quantify phenotypic plasticity. Seasonal dynamics and within-canopy microclimatic effects were also examined, and linked to needle biochemical traits. Residual conductance exhibited a marked seasonal decline, with high values in newly formed needles followed by a stabilization from late summer to the following spring, closely tracking the accumulation of cuticular waxes. In contrast, Klason lignin content showed little seasonal variation. Difference between provenances was weak for all investigated parameters, suggesting strong constraints on these safety-related traits. By contrast, gres showed significant environmental plasticity, with lower values at more climatically constrained sites, while thermal parameters and P50 remained relatively conserved. Our results identify gres as a developmentally dynamic and environmentally plastic trait in silver fir, potentially representing a key lever of acclimation to drought. Incorporating such variability into mechanistic models should improve predictions of tree vulnerability under future climates combining intensified droughts and heatwaves. Key message.Residual conductance in Abies alba is developmentally dynamic and environmentally plastic but genetically constrained, highlighting its key role in acclimation to drought and heatwave-driven hydraulic failure.

Belowground, plants are exposed to a wide range of biotic stresses that vary in severity and nature, including tissue damage, disruption of vascular connectivity, and depletion of assimilates. How plants adapt their root systems to cope with different types of belowground biotic stresses is not well known. In this paper we compare above- and belowground plant adaptations to three nematode species with distinct tissue migration and feeding behaviours to study mechanisms underlying tolerance to different types of biotic stresses. We monitored both green canopy growth and changes in root system architecture of Arabidopsis inoculated with Pratylenchus penetrans, Heterodera schachtii, and Meloidogyne incognita. This revealed three distinct phases in aboveground plant responses: (i) initial growth inhibition associated with host invasion and tissue damage, (ii) persistent growth reduction associated with nematode sedentarism, and (iii) late growth stimulus in more advanced stages of infection. Specific adaptations in the root systems further revealed fundamentally different stress coping strategies. Tissue damage and intermittent feeding by P. penetrans in the root cortex did not induce significant changes in root system architecture. Tissue damage to the root cortex and prolonged feeding on host vascular cells by H. schachtii induced secondary root formation compensating for primary root growth inhibition. Prolonged feeding on host vascular cell by M. incognita alone did not induce secondary root formation, but was accompanied by typical local tissue swelling instead. Our data suggest that local secondary root formation and tissue swelling are two distinct compensatory mechanisms underlying tolerance to sedentarism by root-feeding nematodes. HighlightHow plants utilize root system plasticity to cope with different types of biotic stresses by root feeding nematodes remains largely unknown. Here, we report on specific adaptive growth responses in Arabidopsis roots to three nematode species, Pratylenchus penetrans, Heterodera schachtii, and Meloidogyne incognita, with fundamentally different strategies for host invasion, subsequent migration through host tissue, and feeding on host cells.

Juncus bufonius L. s.l. is a species complex with several ploidy levels, for which species delimitation remains unclear due to a lack of reliable morphological characters and the paucity of molecular studies. To clarify taxonomic and geographic relationships in the complex, we combined genomic, cytometric and morphological data from a broad latitudinal range from England down to Spain. We collected morphometric and cytometric data from 31 populations, and genomic data were obtained through Hyb-Seq using the Angiosperm353 kit for a subset of individuals. These three datasets were combined to explore phylogenetic relationships, population structure, and the validity of four previously proposed morphospecies (J. bufonius s.str., a hexaploid; J. minutulus, a tetraploid; and J. ranarius and J. hybridus, both diploids). Sequencing supported the separation of diploids and polyploids as two distinct taxa, but morphometric characters used previously to describe morphospecies showed continuous variation with no diagnostic value, and were not congruent with genomic and cytometric data. Polyploids likely originated through allopolyploidisation from diploids and tetraploids. Phylogenetic lineages were extensively mixed geographically, both for diploid and polyploid taxa, which suggests repeated long-distance dispersal events for both diploids and polyploids, and no separation of taxa by geography. Splitting of diploids into J. ranarius and J. hybridus was not supported. We recommend J. ranarius be treated as a synonym of J. hybridus, and that tetraploids and hexaploids be grouped under J. bufonius. The observed geographical patterns are consistent with high rates of seed dispersal by migratory waterbirds.

Wild plants, particularly those native to xeric environments, are highly adapted to survive under harsh conditions. These adaptive strategies primarily ensure the successful transfer of genetic material to subsequent generations, often independently of fruit size or quality. In contrast, more than 10,000 years of domestication have shifted plant strategies away from survival-oriented traits toward increase in yield and fruit quality. In this study, we characterized both shared and divergent physiological traits contributing to drought tolerance in wild and domesticated watermelon genotypes. Specifically, we compared above- and belowground responses to water limitation in desert watermelon (Citrullus colocynthis) versus these in a watermelon cultivar (Citrullus lanatus). While aboveground responses to water scarcity were largely similar between the two genotypes, pronounced differences emerged belowground. Root biomass and surface area in the cultivated watermelon were predominantly concentrated in the upper soil layers. In contrast, desert watermelon displayed substantial root system plasticity under drought conditions. Although total root biomass remained largely distributed in the upper soil layers, root surface area shifted toward deeper soil layers, indicating enhanced water acquisition from deeper soil layers without additional biomass investment. These findings suggest that domesticated watermelon, despite originating from desert-adapted ancestors, has largely lost the capacity for dynamic root system adjustment in response to spatial and temporal variation in soil water availability.

Glufosinate-ammonium (GA) has been widely used in Midwestern fields, and in recent years a growing number of failures to control waterhemp [Amaranthus tuberculatus (Moq.) Sauer] have raised concerns about the potential evolution of resistance. The goal of this study was to investigate four independent cases of suspected resistance to GA in A. tuberculatus from Illinois using greenhouse, field, and transcriptomics studies. Greenhouse dose-response experiments revealed resistance ratios ranging from 2.2- to 3.4-fold based on survival and from 1.3- to 2.8-fold based on dry biomass relative to a susceptible population. A subsequent field study where one of the populations originated confirmed that twenty percent of treated plants survived the labeled GA field-recommended rate. Screening for other herbicide sites of action revealed that most populations showed reduced sensitivity to atrazine, glyphosate, and imazethapyr, surviving up to three times the field-recommended rates, and to a lesser extent, lactofen and fomesafen. Transcriptomic analysis of plants surviving GA revealed no resistance-associated mutations or differential transcript abundance in the plastidic and cytosolic isoforms of glutamine synthetase. Among the four suspected resistant populations, there were 182 genes differentially expressed relative to two susceptible populations. Different sets of genes were differentially expressed among the populations studied, with only one gene (upregulated relative to two susceptible populations) shared among all four. Many of the differentially expressed genes, including cytochrome P450s, glutathione S-transferases, glycosyltransferases, transporters, and transcriptional regulators, are commonly associated with metabolic resistance. Gene ontology enrichment analyses indicated significant overrepresentation of stress response, defense regulation, and secondary metabolism categories across the populations. Together, these findings provide evidence for the evolution of GA resistance in populations of A. tuberculatus in Illinois. While more in-depth studies are needed to fully characterize the underlying mechanisms, the consistent differential expression of metabolism-related genes and no indication of target-site mechanisms points to a potential metabolic basis for resistance.

Breadfruit (Artocarpus altilis (Parkinson) Fosberg) is a culturally and nutritionally significant perennial crop of the Pacific Islands. National Tropical Botanical Gardens Kahanu Garden (Maui, Hawai i) maintains a breadfruit collection representing more than 150 traditional varieties, some unique or irreplaceable and requiring safety duplication to safeguard genetic diversity. However, aging trees exhibit variable vigor, potentially limiting clonal propagation outcomes. We assessed air layering as a strategy for conservation duplication, conducting 163 air-layer attempts across 26 priority accessions. We evaluated the influence of tree vigor, age, and branch characteristics on rooting success and survival to out-planting. Overall, 17% successfully rooted and 75% of those survived to out-planting, resulting in successful duplication of 16 of 26 at-risk accessions. Rooting success differed among vigor classes (33% for high-vigor trees; 11-16% for normal and feeble trees) and increased modestly with source tree age, while survival to out-planting declined with increasing age. Branch length and fruiting season were not associated with outcomes. These findings indicate that air layering can support conservation propagation in living collections, but success is strongly influenced by source tree age and condition. Initiating safety duplication while trees are physiologically robust is likely to improve long-term conservation outcomes.

Little is known about environmental drivers of opportunities for hybridization, but its phylogenetic distribution across species and areas is heterogeneous, suggesting that ecological traits may play an important role in concert with postzygotic isolation. Because plant-pollinator interactions are responsible for gene flow in most plant species, differences in the mosaic landscape of plant-pollinator interactions could explain why some plants are particularly prone to hybridization. Prezygotic isolation is mediated by sometimes complex pollen presentation; conversely, conserved pollination strategies would lead to evolutionary constraints on pollinator assemblage divergence in the speciation process and therefore predict higher opportunities for gene flow, although this hypothesis has yet to be tested. The plant taxonomic tribe Heuchereae (Saxifragaceae) is a well-characterized system for pollinator interactions and particularly for floral scent, the primary pollinator attractant in the group. Floral volatile organic compounds (VOCs) in this clade are hypervariable at the population level and are thought to be responsible for pollination selectivity, leading to divergent pollinator assemblages. Observing a contrast of hybridizing and non-hybridizing species, the levels of attractant divergence may therefore predict levels of hybridization. We investigated pollination biology in the plant genus Heuchera, notable for frequent interspecific gene flow compared to tribal relatives, asking whether high rates of hybridization may be associated with low interspecific divergence of VOCs and the pollinator assemblages they shape, using as our system the hybrid zone between H. americana var. americana and H. richardsonii in the midwestern USA. We optimized a closed-space collection and GC-MS (gas chromatography-mass spectrometry) protocol to characterize VOCs in Heuchera flowers. To identify floral visitation and effective pollinators we conducted pollination observations at 40 Heuchera populations over the span of two field seasons. GC-MS data from 89 Heuchera specimens representing 69 populations suggests that classes of VOCs, and to a large extent individual compounds, are shared within the hybrid complex while other Heuchera that are not thought to hybridize with these species have distinct species-specific compounds. Pollination observations and metabarcoding of pollinator pollen loads confirm shared effective pollinators in the hybrid zone and between adjacent parental populations. Attractant and visitation data considered together suggest that conservatism of pollinator interactions may be a typical feature associated with frequent hybridizers, perhaps arising from developmental or biochemical constraints on prezygotic isolation, and more broadly that the macroevolution of isolation mechanisms may be predictive of natural hybridization rate.

Chickpea is predominantly grown under rainfed conditions in regions where terminal drought limits yield, yet little is known about how this stress influences both vegetative allocation and reproductive dynamics leading to altered grain composition. We imposed a controlled terminal drought, with a rewatered treatment group, on three Desi cultivars (ICC4958, ICC1882 and CBA Captain) reported to have contrasting drought tolerance, quantifying vegetative biomass, reproductive node productivity across developmental regions and grain macronutrient composition. Under drought, vegetative responses reflected genotype-specific resource partitioning strategies particularly evident in severe root degradation and increase stem dry matter content that was only partially alleviated in rewatered plants. Reproductive outcomes were strongly influenced by developmental stage at the time of stress, with increased pod abortion observed particularly at nodes initiating seed development under drought treatment. Grain composition of seeds filled under drought was significantly altered by stress, with increased protein concentration and decreased starch content under both Drought and Recovery treatments independent of cultivar, likely due to water limitation at crucial filling stages. These findings demonstrate that the developmental timing of terminal drought interacts with cultivar growth strategy to influence pod production and grain nutritional quality in chickpea. HighlightThe developmental timing of terminal drought interacts with cultivar-dependent growth strategies to influence pod productivity and grain nutritional quality in chickpea.