AoB PLANTS

PremiseMosses provide many ecosystem functions and are the most vulnerable of biocrust organisms to climate change due to their sensitive water relations stressed by summer aridity. Given their small size, moss stress resistance may be more dependent on fine-scale habitat than macroscale (climate and community), but this sheltering role of habitat (i.e. habitat buffering) has never been compared to macroclimate and may have important implications for predicting critical biocrust refugia in changing climates. MethodsWe located three populations of a keystone biocrust moss, Syntrichia caninervis, spanning 1200-m of altitude comprising three plant communities (elevation-plant zones) in the Mojave Desert. We stratified 96 microsites along three habitat aridity gradients: elevation-zone, topography (aspect), and microhabitat (shrub proximity). We estimated summer photosynthetic stress (Fv/Fm) and aridity exposure (macroclimate, irradiance, and shade). ResultsMicrosite aridity exposure varied greatly revealing exposed and buffered microhabitats in all elevation-zones. Moss stress did not differ by elevation zone despite the extensive macroclimate gradient, failing to support the high-elevation refugia hypothesis. Instead, stress was lowest on N-facing slopes and microhabitats with higher shrub shading, while the importance of (and interactions between) topography, irradiance, and shade varied by elevation zone. ConclusionsWe demonstrate fine-scale habitat buffering is physiologically more protective than high-elevation climate, and thus, may allow some mosses to hide from the brunt of climate change in widespread microrefugia throughout their current ranges. Our findings support a scale-focused vulnerability paradigm: microrefugia may be more important than macrorefugia for bolstering biocrust moss resistance to summer climate stress.

O_LIAccounting for intraspecific variation may improve our understanding of species coexistence. However, our knowledge of what factors maintain intraspecific variation is limited. We predicted that 1) a plant grows larger when with non-kin (i.e. different genotypes) than kin (i.e. same genotype) neighbors, 2) abiotic stress alters the outcome of kin vs. non-kin interactions, 3) genetic identity of plants affects composition of soil microbiome. C_LIO_LIWe set up mini-communities of Medicago truncatula, where focal genotypes were grown together with two kin or two non-kin neighbors from different origins. We analyzed how origin, identity of interacting genotypes and abiotic stress affected growth and fruit production. We also analyzed the composition of soil microbial communities. C_LIO_LIFocal plants grew larger in non-kin than in kin mini-communities. This pattern was stronger in low level of abiotic stress and when interacting genotypes were from similar origins. However, genotypic variation in growth and response to competition had a stronger effect on growth than mini-community type. Plant genotype identity did not affect soil microbiome. C_LIO_LIWe find that intraspecific variation is affected by genotype-specific traits and abiotic stress. Geographic, rather than genetic, distance among interacting genotypes affects the outcome of intraspecific interactions. C_LI

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

Fire stimulates germination of most seeds in fire-prone vegetation. Fruits of Leucadendron (Proteaceae) are winged achenes or nutlets that correlate with their requirements for smoke and/or heat in promoting germination. We describe five possible smoke-heat dormancy-release/germination syndromes among plants, of which Leucadendron displays three (no response, smoke only, smoke and heat). As seed-coat thickness varies with seed-storage location (plant or soil) and morphology (winged or wingless), we tested its possible role in water uptake and germination. Species with winged seeds achieved 100% germination in the absence of smoke/heat, seed coats were an order of magnitude thinner, and their permeability greatly exceeded that of nutlets. As seed-coat thickness increased a) imbibitional water uptake declined at a decreasing rate, and b) the response to smoke, and to a lesser extent heat, increased linearly to reach levels of germination approaching those of winged seeds. For species responsive to smoke and heat, there was no additive effect when applied together, suggesting that they may have promoted the same physiological process. By what mechanisms a) the smoke response is greater the thicker the seed coat, and b) smoke chemicals could increase water permeability to explain the non-additive effect of smoke and heat, warrant further investigation. HighlightWe show Leucadendron seeds are either plant-stored with thin, highly permeable seed-coats that germinate readily; or soil-stored and the thicker their seed-coat, the lower their permeability and greater their need for smoke/heat to promote germination.

Background and aimsIntraspecific variation in functional traits is essential for the evolutionary success of organisms. The co-variation between trait variation and environment, as well as between different traits, can help us to understand which ecological factors drive habitat adaptation, and to what extent adaptation may be constrained by trait correlations and trade-offs. In managed grasslands, plants experience a combination of competition, recurrent biomass removal and nutrient pulses. Each of these ecological challenges requires specific plant tolerances, and populations should locally adapt if intraspecific variation exists in these traits. MethodsWe studied variation in land use-related traits in the common grassland plant Plantago lanceolata. In a common environment, we quantified the competitive ability (R*), clipping tolerance and responses to a nitrogen pulse of plants from 54 populations with different land use intensities across Germany. Key resultsWe found significant population differentiation in competitive ability but there was little evidence that trait variation was related to land use intensity. There was a positive relationship between competitive ability and clipping tolerance at the population level, indicating a genetic, and possibly functional, link between these two traits. In contrast, clipping tolerance and nitrogen responses were negatively correlated at the levels of plant individuals, indicating a physiological trade-off between plant responses to these two land-use processes. ConclusionsOur results show that there is substantial intraspecific variation in some of the key functional traits for plant success in managed grasslands, and that rapid evolution and adaptation is therefore possible in these traits.

This study investigates the contrasting patterns of genetic diversity and local adaptation between old-growth and recently planted Norway spruce (Picea abies) stands in northern Sweden. We assess neutral genetic variation, adaptive genetic differentiation, and the potential for future adaptation using samples collected from old-growth forests and recently planted stands. Our results reveal no significant differences in overall genetic diversity between natural and planted populations, indicating that current forest management practices have not substantially reduced genetic variation. However, analyses of adaptive variation demonstrate stronger signatures of local adaptation in old-growth populations, with clear correlations between genetic and environmental distances. In contrast, planted stands show weaker adaptive signals and are at greater risk of non-adaptiveness under future climate scenarios. These findings highlight the importance of conserving and promoting adaptive genetic variation within forest management to ensure resilience against ongoing climate change, while also recognising that current practices preserve much of the neutral genetic diversity necessary for long-term forest health.

>Mixed-cytotype populations are ideal to understand polyploid establishment and diversification. We used the orchid Zygopetalum mackayi to understand how facultative apomictic reproduction relates to polyploidy. Sexual diploids and facultative apomictic tetraploids occur under distinct niches, with a contact zone where triploids occur. We hypothesized that facultative apomictic reproduction increases the fitness of tetraploids through reproductive interference between cytotypes. We predict patterns of genetic diversity of allopatric tetraploid populations to be significantly different from contact zone populations as a result of dominant apomictic reproduction in the later. We also describe the contact nature of diploids and tetraploids and the role of the intermediate triploids based on patterns of genetic structure within and among pure and mixed-cytotype populations.\n>We designed eight microsatellite markers and genotyped 155 individuals from six populations resulting in 237 alleles. We described patterns of genetic diversity and structure within and among populations and cytotypes.\n>Genotypic diversity is similarly high among all populations and cytotypes. Each cytotype emerged as a genetically cluster, combining individuals from different populations. Triploids clustered in an intermediate position between diploids andtetraploids.\n>We rejected the hypothesis of reproductive interference between cytotypes of Z. mackayi. Patterns of genetic diversity are incongruent with the occurrence of apomict reproduction in tetraploids. Mixed-cytotype populations originate from secondary contact and triploids are hybrids between diploids and tetraploids and act as a reproductive barrier. We suggest polyploidy rather than facultative apomixis explains higher fitness of tetraploids in this species and, therefore, eco-geographical patterns of distribution.

Premise of researchHermaphroditic plants reproduce as females by maturing seeds from fertilized ovules and as males by fertilizing the ovules of other plants. Sex allocation theory predicts a trade-off between investment in male and female function. Thus, to maximize fitness, selection should favor plasticity in resource allocation among individuals or flowers of the same plant in response to environmental conditions. As female reproduction is typically more costly while male reproduction is mate-limited, we predict greater investment in female function when resources are plentiful and in male function when pollination is limited. MethodologyWe investigated plasticity in sex allocation in the rapid cycling lineage of the hermaphroditic mustard species, Brassica rapa, in response to resource availability (altered pot size) and the pollination environment (unpollinated or fully pollinated). We assess investment in male function (anther length) and female function (ovary length) in flower buds produced at the onset of reproduction and in buds produced approximately 15 days later. We also measured traits often correlated with increased allocation to female (plant size) and male (flower size) function. Pivotal ResultsLarger plants had longer anthers, longer ovaries, and larger flowers at the onset of reproduction, resulting in similar anther:ovary length ratios across plants of different sizes. Independent of plant-size, plants produced smaller anthers at the onset of reproduction in the low resource treatment and larger flowers over the course of reproduction in the pollen-absent treatment. Furthermore, larger plants produced increasingly longer ovaries over the course of reproduction compared to smaller plants. ConclusionsOur findings underscore the influence of condition on changes in sex allocation and correlated traits over time. Furthermore, we provide some additional supporting evidence that resource availability and the pollination environment can influence sex allocation and contribute cautionary advice on effective methods for experimentally eliciting and measuring sex allocation plasticity.

How agricultural regimes, such as novel herbicide exposure, may influence plant-herbivore interactions and specifically patterns of plant herbivory has come under increased interest in recent years due to rapidly changing herbicide use in agroecosystems. This paper examines patterns of plant herbivory using three common agricultural weeds exposed to low doses of dicamba, a synthetic auxin herbicide that is exponentially increasing in use given the adoption of dicamba tolerant crops. We used a replicated field study to examine how the amount and type of chewing herbivory may be altered in Ipomoea purpurea (common morning glory, Convolvulaceae), Datura stramonium (jimsonweed, Solanaceae), and Abutilon theophrasti (velvetleaf, Malvaceae) exposed to dicamba drift (i.e., 1% of the field dose). We found an increase in chewing herbivory damage when plants were exposed to dicamba and changes in the type of herbivory following exposure. Chewing herbivory differed among species in the presence of dicamba drift: A. theophrasti and D. stramonium showed more total leaf-chewing herbivory than controls, but I. purpurea showed no difference in the overall amount of herbivory. We also found that the type of herbivory was significantly altered in drift. A. theophrasti and I. purpurea both exhibited declines in hole feeding but increases in margin feeding, whereas D. stramonium showed no such changes. Overall, our results show that herbicide drift can induce shifts in plant-herbivore interactions, highlighting the need for mechanistic studies to uncover the cause underlying the shifts and comparative studies on weed communities to understand long-term consequences.

O_LIClimate change impacts arctic latitudes more acutely than other latitudes, resulting in arctic shrubification. How individual species in these climes respond to warming temperature is poorly understood. Understanding species resiliency to climate change will help us conserve plant species at risk. C_LIO_LIWe performed a survey of plants in a permafrost anomaly in Resolute (Qausuittuq), Nunavut, Canada. Two identified species, Stellaria longipes Goldie and Cerastium regelii Ostenf., were investigated through modelled niche suitability under future climate scenarios, phenological analysis, and in vitro warming experiments to investigate growth and phytochemical profiles. C_LIO_LI10 species including Stellaria longipes and Cerastium regelii were identified in the anomaly. Predicted niche suitability increased under SSP126 for C. regelii, with compressed and later flowering period since 1850. In vitro, S. longipes maximized growth at 24 {degrees}C with greater abundance of cytokinins than C. regelii, which increased growth at 28 {degrees}C. C_LIO_LIStellaria longipes is self-limiting at higher temperatures, and is less temperature-dependent for its success, while C. regelii is more affected by warming temperatures, showing increases in growth and predicted niche suitability. Our work increases understanding of plant resiliency and vulnerability in Canadas High Arctic, and sheds light on the biology of an understudied arctic specialist in C. regelii. C_LI

Anthropogenic climate change and land-use changes threaten the health and survival of plants, particularly by altering the microclimatic conditions of habitats. Plant productivity is highly sensitive to these abiotic conditions that influence their morphological and physiological traits. I studied this relationship in plants of the Arctostaphylos genus, commonly known as manzanita, shrubs in chaparral ecosystems across California. I assessed microclimate and examined its effects on leaf morphological traits and plant productivity of A. crustacea ssp. crustacea across two sites in Alameda County, California. At the site of higher sunlight and less soil moisture (VWC), leaves had a greater mass per area (LMA) and were more steeply angled, and photosynthesis was significantly higher (11.14 {micro}molCO2/m2s) than leaves at the site of less sunlight and more VWC (7.94 {micro}molCO2/m2s). Results from linear mixed models showed that light level was the overall strongest predictor variable for plant traits, with vapor pressure deficit and VWC also contributing to LMA, and leaf temperature and leaf angle distribution also influencing photosynthesis. Overall, no individual microclimatic variable was the sole contributing predictor of a leaf morphological trait or photosynthesis. Rather a combination and interaction of microclimatic conditions influenced plant functional traits, though some conditions had greater influence than others. The functional traits of A. crustacea ssp. crustacea adjusted in response to microclimatic factors, showing intraspecific trait variation (ITV) of this species. ITV is an essential defense for plant resilience that allows for adaptations in the face of rapidly changing climatic conditions.

Recent habitat change in semi-natural grasslands due to a lack of management has been shown to affect the genetic diversity of grassland plants. However, it is unknown how a change in local environment affects genetic diversity at adaptive loci. We applied RADseq (restriction-site associated DNA sequencing) to extract > 3,000 SNPs across 568 individuals from 32 Estonian populations of Primula veris, a plant species common to semi-natural grasslands. We evaluated the effect of recent grassland overgrowth following management abandonment on the genetic diversity at putatively neutral and adaptive loci, which we distinguished by applying three methods, i.e., linear and categorical environmental association analyses, and an FST outlier test. For validation, we randomised the genotype to sample assignments. Effects of recent habitat change on genetic diversity differed between neutral and adaptive SNP sets. Genetic diversity assessed at putatively neutral loci was similar in open and overgrown habitats but showed a significant difference between these habitat types at putatively adaptive loci: overgrown (i.e. newly established) habitats exhibited higher genetic diversity at putatively adaptive loci than open (i.e. old) habitats, likely due to the exertion of novel selection pressures imposed by new habitat conditions. This increase in genetic diversity at putatively adaptive loci in the new environment points to currently ongoing selection processes where genetic adaptation to the old habitat is potentially lost through altered allele frequencies. Our study suggests that a recent change in local habitat conditions may not be reflected in neutral loci whereas putatively adaptive loci can inform about potential selection processes.

Water availability is perhaps the greatest environmental determinant of plant yield and fitness. However, our understanding of plant-water relations is limited because it is primarily informed by experiments considering soil moisture variability at two discrete levels - wet and dry - rather than as a continuously varying environmental gradient. Here we used experimental and statistical methods based on function-valued traits to explore responses to a continuous soil moisture gradient in physiological and morphological traits in two species and five genotypes each of the model grass Brachypodium. We find that most traits exhibit non-linear responses to soil moisture variability. We also observe differences in the shape of these non-linear responses between traits, species, and genotypes. Emergent phenomena arise from this variation including changes in trait correlations and evolutionary constraints as a function of soil moisture. These results point to the importance of considering non-linearity in plant-water relations to understand plastic and evolutionary responses to changing climates.

BackgroundUnderstanding the ability of species to respond to climate change is essential for prediction of their future distribution. When migration is not adequate, reaction via phenotypic plasticity or genetic adaptation is necessary. While many studies investigated the importance of plasticity and genetic differentiation (plant origin) in growth related traits, we know less about differentiation in ecophysiological traits. In addition, the existing studies looking at plant physiology usually do not estimate the consequences of these physiological changes for species performance. MethodsWe used a clonal grass Festuca rubra originating from localities representing factorially crossed gradients of temperatures and precipitations. We cultivated the plants in growth chambers set to simulate temperature and moisture regime in the four most extreme localities. We measured net photosynthetic rate, chlorophyll fluorescence, SLA, osmotic potential, stomatal density and stomatal length as range of ecophysiological traits and tested their relationship to plant fitness measured as ramet number and biomass. Key resultsWe found strong phenotypic plasticity in photosynthetic traits and genetic differentiation in stomatal traits. In most traits, the effects of temperature interacted with the effects of moisture. The relationship between the ecophysiological and fitness-related traits was significant but weak. ConclusionsEcophysiological response of Festuca rubra to climate change is driven by phenotypic plasticity as well as by genetic differentiation indicating potential ability of the populations to adapt to new climatic conditions. The changes in ecophysiological traits translate into plant fitness even though other unmeasured factors also play an important role in fitness determination. Inclusion of species ecophysiology into studies of species adaptation to climate can still increase our ability to understand how species may respond to novel conditions.

The effects of urbanization on watershed ecosystems present critical challenges to modern survival. Organisms in urbanized areas experience high rates of evolutionary change, but genetic adaptation alone cannot mitigate the rapid and severe effects of urbanization on biodiversity. Highly resilient, foundation species are key to maintaining an ecosystems integrity in the face of urban stressors. However, the rapid collapse and disappearance of watershed ecosystems calls into question the extent to which we can rely on such species for their services. Our research investigates the molecular mechanisms by which the foundation ecosystems provider, Sporobolus alterniflorus, adapts to life in an urbanized environment. To elucidate these mechanisms, we quantified changes in global DNA methylation (% 5-mC) as a result of acute heat stress. Specimens from two differentially impacted populations across an urban to suburban geographical transect formed the basis of this study. These two populations of Sporobolus alterniflora exhibit inverse global DNA methylation patterns when exposed to the same acute heat stress. Our findings suggest that epigenetic mechanisms, such as DNA methylation, control rapid and transient adaptation, in the form of differential stress responses, to distinct environment challenges. Highlights for manuscript submissionO_LI{blacksquare} estuarine grasses native to the Bronx River, NY face stresses associated with low dissolved oxygen and urbanization C_LIO_LI{blacksquare} differentially impacted populations of estuarine grasses exhibit inverse global DNA methylation profiles in response to acute heat stress C_LIO_LI{blacksquare} DNA methylation may represent a mechanism by which plants transiently respond to environmental stressors, and this may represent a form of rapid adaptive evolution C_LIO_LI{blacksquare} stress priming by transgenerational epigenetic modification may enhance fitness in grasses native to the heavily impacted Bronx River estuary C_LI

ContextAbiotic stress, and particularly drought, is a major threat to plant growth generally and world food security specifically and it is important for humanity to come up with ways to reduce the impact of drought and abiotic stress on plant growth. This is particularly important in the context of global climate change. Earlier research by a range of researchers has hinted that the use of cheap citric acid in treating plants may induce enhanced stress response pathways which may assist in enhancing drought tolerance. However, how altered stress response pathways affect plant growth patterns, and how these may affect drought tolerance, has not been well researched. MethodsSpotted Gum seedlings were grown with and without initial treatment with citric acid, and with and without simulated drought. Key resultsTreatment with citric acid resulted in plants growing larger and more fibrous root systems compared to control plants. The effect was stronger under moderate drought. ImplicationsExogenous treatment of cotyledon roots with citric acid has tremendous potential for enhancing plant root systems under moderate drought. Resulting enhanced root systems could be expected to enhance a plants access to soil water and thus improve drought tolerance. Reduced shoot to root ratios could also be expected to improve drought tolerance of young plants in the early growth phase. SummaryIn addition to potentially having a negative effect on mine revegetation drought remains one of the major causes of agricultural loss globally, threatening food security. A range of research has hinted at the role of citric acid in plant stress response and particularly in drought tolerance (Godbold et al. 1984; Shlizerman et al. 2007; Sun and Hong 2011). It was reported that Arctic tundra soils contain high levels of citric acid (Jones 1998). Jones posed the question as to the relevance of citric acid in plant stress response and particularly to drought tolerance in environments where liquid water is limited. In order to discover whether citric acid might be used to enhance plant growth patterns leading to enhanced drought tolerance in woody species used in large scale mine rehabilitation, a series of trials were established. In these, the roots of cotyledons of commonly used species including Spotted Gum (Corymbia maculata) were soaked in various concentrations of citric acid in order to examine the effect on early plant growth. This paper discusses the results of one of these experiments conducted at the University of Newcastle as part of the authors PhD program. A range of responses were noted in treated seedlings including the development of larger and more fibrous root systems. This response was stronger in plants subject to moderate drought and suggested that treatment enhanced an existing stress response pathway that affected root growth. This significantly enhanced root effect had not been previously noted in response to treatment with citric acid. Other beneficial effects were noted including the enhancement of shoot to root ratio and subsequent enhanced shoot growth as a result of larger and more fibrous root systems. Results from the study raised the question as to how widespread these effects are in the broader plant kingdom and what might be the relevance to food crop production? In this context, further research was undertaken on seeds and tissue culture of key crop species and the results, including significant effects on leaf gas exchange, and this will be reported in later papers. As such, it should be noted that this paper is part of a much larger research program in which the effect of citric acid treatment on cotyledons, seed and tissue culture of a range of woody C3 species is examined. Summary text for journal table of contentsDrought, induced through global climate change and other factors, is likely to cause major conflict through its effect on plant establishment and food security in particular. Using Australian Spotted Gum trees as a subject, this experiment shows that the use of cheap citric acid on seedlings can produce growth effects such as enhanced fibrous root growth that, among other benefits, may make them significantly more drought-tolerant. The results may be beneficial to commercial forestry but may also have major implications for food security worldwide if observed effects are relevant to food crop species. Table of contents graphic O_FIG O_LINKSMALLFIG WIDTH=177 HEIGHT=200 SRC="FIGDIR/small/513958v1_ufig1.gif" ALT="Figure 1"> View larger version (126K): org.highwire.dtl.DTLVardef@947a3org.highwire.dtl.DTLVardef@13e4347org.highwire.dtl.DTLVardef@b31817org.highwire.dtl.DTLVardef@1f29170_HPS_FORMAT_FIGEXP M_FIG C_FIG

Background and AimsPlants display enormous variation in the phenological traits that make up their life cycle both within and between populations. Facultative winter annual species are particularly interesting because they can adopt either a fall-emerging/spring-flowering or spring-emerging/summer-flowering life cycle at the population level via evolution or at the individual level via within-generation and transgenerational plasticity. Responses of phenological traits to the environment have often been found to be mediated by changes in hormone levels, especially the growth hormone gibberellic acid (GA). MethodsWe conducted growth chamber and greenhouse experiments using the facultative winter annual agricultural weed Erigeron canadensis (horseweed) to investigate the interactive effects of genetic variation; parent plant life cycle; and plastic responses to temperature, light, and GA treatments. Key ResultsWe found that contrary to a prior report, exposing imbibed seeds to 3-4 weeks of cold (i.e., seed vernalization) does not always result in summer annual type growth, with considerable variation found among field-collected seeds from 10 populations. Further, we found that seed vernalization and exogenous application of GA both tended to increase summer annual characteristics, interacting in ways that were largely consistent with the hypothesis that GA is a mechanism for cold-induced life cycle differentiation. Light treatment did not significantly affect life cycle traits, while parent life cycle type had marginal effects on offspring life cycle type. Finally, genetic variation among and within sites explained far less of the variation in life cycle traits than the plastic responses to seed vernalization and GA treatments. ConclusionsOur study proposes that the seasonality of this harmful agricultural weed is influenced by a GA-mediated response to vernalization of seeds during winter, yet highlights the need for further study, given the variability in this response.

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.

As climate change threatens agricultural yields, crop diversification, including the reintroduction of underutilized species, has emerged as a proposed solution for resilience. But what determines the extent of environmental change that underutilized crop species can cope with upon their reintroduction? One critical factor is maladaptive plasticity, a theoretical concept suggesting that populations may respond negatively to rapid environmental shifts, at least in the short term. To test this empirically, we conducted a repeated-measures study using historically underutilized Amaranthus species as a model. Upon reintroduction, we observed higher plasticity in vegetative and reproductive traits than in life-history traits. This suggests that while these species adapt to immediate environmental changes through adjustments in growth and reproduction, limited plasticity in life-history traits may constrain long-term adaptation. Our study aimed to (1) identify the environmental factors driving these plastic responses, (2) determine whether these responses are maladaptive, and (3) assess if maladaptive plasticity also occurs within native environments. Using machine learning models, we found that temperature was a primary driver of plastic responses. Generalized Additive Model (GAM) reaction norm analysis further revealed these temperature-induced responses to be maladaptive, suggesting a mismatch between Amaranthus traits and the new environment. Applying transfer learning to predict responses in native settings, we found similar maladaptive responses to temperature, indicating that maladaptive plasticity may not be limited to non-native environments, thereby complicating climate adaptation efforts. This study underscore the need for detailed trait plasticity assessments before crop reintroduction for agricultural resilience.

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.