Aim Peripheral regions of the Alps are often overlooked in molecular studies, yet they may play a major role in shaping the current distribution of species and genetic lineages.Location Europe.Taxon Angiosperms (Primulaceae: Primula).Methods By focusing on the bear's ear (Primula auricula) complex as model species, we used genetic inferences for population genetic structure and performed genetic reconstructions, species delimitations and divergence time estimates in order to get a detailed view of its molecular evolution and current genetic structuring across the Alps sensu lato.Results The Lombardian Alps and the southern eastern Alps are genetically distinct in the vicinity of the Adige valley. The northern and western Alps and their peripheries constitute a third clade and are separated by the siliceous central Alps. Within the latter, an additional cluster made of singular populations from the D & eacute;voluy and Vercors regions is retrieved, likely reflecting a strong founder effect rather than an ancient divergence.Main Conclusions The biogeographic history P. auricula sensu lato pinpoints the importance of the peripheral regions in a phylogeographic context. Populations from northern peripheral regions exhibit long-lasting isolation and in situ survival during glaciations, followed by recolonisation into the central Alpine massif.

Abstract Understanding how defense strategies differ within species across environmental gradients is crucial for predicting plant–herbivore interactions under shifting ecological conditions. Intraspecific variation in inducible defenses, particularly root–shoot systemic induction (RSI), may be influenced by ecological divergence, but its evolutionary potential remains largely unknown. We investigated ecotypic differentiation and genetic variation in RSI in Cardamine pratensis along an elevation gradient. Our approach combined a field survey of natural populations with a reciprocal common garden experiment using maternal families from both high- and low-elevation ecotypes. We measured constitutive and Jasmonic Acid (JA)-induced glucosinolate (GSL) production, as well as resistance to natural herbivory. Low-elevation ecotypes experienced greater belowground arthropod community abundance and produced higher baseline GSL levels, while high-elevation ecotypes invested less in constitutive defenses but exhibited stronger plasticity in specific GSL compounds. across both field and common garden experiments, JA application to roots consistently reduced leaf herbivory, indicating widespread RSI across ecotypes. However, RSI occurred independently of total foliar GSL levels, suggesting that systemic resistance is not explained by variation in measured GSL induction. Family-level variation in the effects of RSI on herbivory was observed, especially in high-elevation ecotypes, indicating genetic differences that could support the evolution of systemic inducibility. These findings collectively show that RSI contributes to herbivore resistance across different environments, although defense allocation patterns vary between ecotypes. Root-induced resistance appears to be a flexible part of plant defense, capable of changing across ecological gradients through both phenotypic plasticity and genetic variation differentiation.

Temperature influences the distribution and performance of both plants and insect herbivores. Consequently, plant-herbivore interactions are likely to vary across thermal gradients, which could affect the evolution of plant defense. Furthermore, temperature fluctuations may elicit immediate changes in defense. To study the evolutionary and ecological aspects of plant antiherbivore defense depending on temperature, we conducted a transplant experiment on a mountain slope involving 30 Brassicaceae species varying in elevational distribution. Additionally, we carried out a climate-chamber experiment on a subset of 12 species to assess the temperature dependence of constitutive and induced defenses. The transplant experiment revealed that species from higher elevations experienced less herbivory than those from lower elevations. The climate-chamber experiment demonstrated that high-elevation species mounted stronger induced defenses in physical properties of leaves and in phytochemical diversity. Plant responses to low temperature, compared to control temperature, were lower constitutive defense and increased defense induction limited to leaf toughness. By contrast, high temperature increased constitutive chemical defense and defense-induced leaf toughness. Results suggest higher herbivory resistance in high-elevation Brassicaceae species by the induced remodeling of chemical defense. Such defense indication may have been shaped by rare but hard-to-tolerate herbivory in the evolutionary past.

Understanding how evolutionary history and ecological pressures shape plant chemical diversity is central to ecology and evolution, yet it remains unclear whether metabolomic data can reliably detect fine-scale, intraspecific divergence, particularly in morphologically cryptic taxa. While metabolomics has revealed broad patterns of chemical evolution across lineages, its power to resolve genetically structured variation within species is still underexplored. Here, we investigated the alpine Primula auricula complex, a morphologically uniform but genetically subdivided taxon distributed across the Alps. Using ultra-high-performance liquid chromatography coupled with mass spectrometry, we profiled the metabolomes of individuals sampled from 37 populations spanning three main genetic clades and an outlier group, previously identified through ddRADseq phylogeography. We found that metabolomic diversity carries a strong phylogenetic signal: each clade exhibited distinct chemical profiles, with exclusive or enriched metabolite superclasses such as carotenoids in one clade and phenylpropanoids in another. Outlier populations displayed reduced metabolomic richness, consistent with potential genetic drift or bottlenecks. While phylogenetic structure was the dominant driver of chemical variation, climatic variables, particularly temperature and precipitation, modulated certain stress-related metabolite groups, such as octadecanoids. Our results demonstrate that metabolomic profiling can capture both historical divergence and ecological adaptation in cryptic alpine taxa. By linking chemical, genetic, and environmental variation, this study highlights metabolomics as a cost-effective and high-resolution approach to uncover cryptic diversity, refine taxonomy, and inform conservation strategies in biodiversity hotspots increasingly threatened by climate change.

Carnivorous plants have evolved specialized adaptations that allow them to persist in nutrient-poor habitats, including modified traps, digestive enzymes, and mechanisms for absorbing nutrients derived from prey. Beyond these structural features, chemical signalling mediated by volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) contributes to several ecological functions, such as prey attraction, short-range interactions, and defence. VOCs can attract insects over relatively long distances, whereas SVOCs tend to remain on trap surfaces, where they may influence local interactions with arthropods and microbes. Environmental conditions, particularly precipitation and humidity, are known to affect VOC emissions and may alter foraging dynamics, yet the extent to which variation in chemical emissions corresponds with differences in prey capture is still not well resolved. To address this knowledge gap, we performed a study under both field and greenhouse conditions using the carnivorous plant Drosera rotundifolia in two climatically contrasting sites of north-western Spain: the wetter Serra do Cando (CP) and the drier Serra de Ancares (AP). At both sites, we quantified insect prey capture and characterized VOC and SVOC emissions. Prey capture rates were similar between regions, but plants from the drier site showed higher total VOC emissions, while SVOC production did not differ markedly. PERMANOVA analyses further indicated that site had no significant effect on overall VOC or SVOC composition. Together, these results suggest a balance between flexibility in emission intensity and stability in chemical composition, providing insight into how specialized metabolites support the ecological functioning of carnivorous plants across contrasting environmental conditions.

Herbivore-induced plant volatiles (HIPVs) are known to prime neighboring plants for enhanced defense, but the molecular basis for this phenomenon remains poorly understood, particularly in cotton. Here, we demonstrate for cotton plants that exposure to volatiles induced by the cotton bollworm ( Helicoverpa armigera Hübner; CBW), enhances resistance against subsequent CBW attack, as evidenced in both laboratory and semi-field trials. While HIPV exposure alone did not elicit direct defense activation, it primed the jasmonic acid (JA) signaling pathway, leading to accelerated induction of JA biosynthesis genes and elevated JA accumulation upon herbivory. That this primed resistance is JA-dependent, was confirmed by treating HIPV-exposed plants with JA biosynthesis inhibitors, which completely abolished the priming effects. We further found that HIPV-primed plants exhibited significantly higher accumulation of the key defensive metabolite gossypol following larval feeding. The role of gossypol-reliant defenses was confirmed by using a glandless cotton mutant ( gl 2 gl 2 gl 3 gl 3 ) deficient in gossypol and related terpenoid aldehydes. The combined results reveal that CBW-induced volatiles prime anti-herbivore resistance in cotton by potentiating the JA signaling pathway, which in turn enhances gossypol biosynthesis upon actual herbivore attack. This new insight into the physio-ecological mechanisms underlying airborne defense priming in cotton also highlights its potential application in sustainable pest management.

Abstract As glaciers retreat worldwide, newly exposed terrains are rapidly colonized by plants and their associated animal communities. Although plant–animal interactions are key for biodiversity maintenance and ecosystem functioning, the ecological processes underlying the assembly and development of trophic interactions over space-time remain poorly understood. Here, we investigated the trophic niche structure of plant–arthropod interactions along a 140-year primary succession at Mont Miné glacier foreland (Switzerland). Using arthropod gut-content DNA metabarcoding, we reconstructed trophic interactions at the food web level, revealing numerous previously undetected links among 284 arthropod taxa feeding on 263 plant taxa. Trophic niche overlap among arthropods increased following glacier retreat, indicating decreasing resource partitioning and suggesting increased resource competition. Trophic niche breadth became narrower and diet species richness declined, indicating increased trophic specialization. Notably, changes in trophic interactions occurred more rapidly than shifts in species diversity or community composition of plants and arthropods. These results demonstrate that glacier retreat reorganizes trophic networks beyond simple species turnover, reshaping biotic interactions during ecosystem development. Our findings highlight trophic interactions as sensitive indicators of biodiversity change and suggest that the stability of emerging food webs may be strongly affected as glaciers vanish worldwide.

Photorhabdus bacteria are potent insect-killing microbes associated with entomopathogenic nematodes and offer opportunities for environmentally benign pest control. They can be applied as foliar sprays or soil drenches without their nematode vector, resulting in massive amounts of Photorhabdus cells and their (toxic) metabolites introduced into the soil. Their impact beyond the target organisms, soil microbial communities and plant physiology and resistance remain unclear. To fill this knowledge gap, we investigated the soil legacy effects of Photorhabdus cells and their metabolites on soil microbial communities, plant performance and resistance to herbivores. To this end, we first conditioned soils with i) mechanically killed (MK) or Photorhabdus-infected insect larvae, ii) aqueous extracts of MK or Photorhabdus-infected insect larvae, iii) cell-free Photorhabdus supernatants, iv) autoclaved soil complemented with live soil previously conditioned with MK or Photorhabdus-infected insect larvae. We then grew maize plants in these soils and measured plant biomass, profiled soil microbial communities and plant metabolites, and evaluated plant resistance against two pest insects Diabrotica balteata and Spodoptera frugiperda. We found that conditioned soils increased plant biomass by 10-26% relative to controls and significantly altered soil bacterial and nematode communities, and to a lesser extent, fungal communities. Re-inoculating conditioned soil microbiota into autoclaved soils recreated the plant growth-promoting effects, indicating microbial-mediated mechanisms. Additionally, plants grown in soils conditioned with Photorhabdus-infected insect cadavers were often more resistant to herbivorous insect attack, in a strain-specific manner. On average, D. balteata and S. frugiperda larvae gained 10-20% and 10-59% less weight, respectively, when fed on plants grown in conditioned soils than on plants grown in control soils. The plant metabolic profiles of plant leaves and roots also varied with resistance levels. We conclude that Photorhabdus metabolites modulate soil microbial communities towards a structure that enhances plant growth and triggers systemic responses against herbivores.

Island biogeography theory predicts that island plants should exhibit reduced defences compared with their mainland relatives due to relaxed herbivory pressure. However, growing empirical evidence challenges this prediction, revealing substantial variation among systems, plant lineages and defence types. These inconsistencies suggest that simple expectations of reduced defence on islands overlook the diversity of selective agents and strategies plants use to cope with herbivores. A more integrative perspective proposes that island – mainland comparisons should simultaneously consider multiple defensive mechanisms, including resistance – both constitutive and inducible – and tolerance‐related traits. In this study, we conducted two complementary greenhouse experiments to examine resistance and tolerance responses in seven island–mainland species pairs of oaks Quercus across three biogeographical regions: Bornholm Island versus mainland Sweden, the Balearic Islands versus mainland Spain, and Lesbos Island versus mainland Greece. Seedlings were exposed to controlled foliar herbivory by the generalist Lymantria dispar , with undamaged plants serving as controls. Resistance was quantified by measuring key chemical defences – namely total phenolic content and volatile organic compounds – assessed both at constitutive levels and in terms of inducibility following herbivore damage. Tolerance, in contrast, was evaluated as the plant's capacity for growth compensation, quantified through height regrowth after herbivory. Our results show that, contrary to traditional expectations, island and mainland oak seedlings did not differ significantly in either chemical resistance or growth‐based tolerance to herbivory. These results suggest that the evolution of plant defences on islands may not be universally reduced and that both island and mainland oaks maintain comparable strategies to cope with herbivory, highlighting the importance of considering multiple defence mechanisms and local ecological contexts when assessing insularity effects.

1. Understanding how intraspecific variation in functional traits shape species interactions is central to predicting ecological responses to environmental change. The relative contribution of genetic differentiation and phenotypic plasticity to trait variation and their consequences for species interactions remain poorly understood. 2. Here, we conducted a reciprocal transplant experiment using Plantago lanceolata along an elevation gradient in the Eastern Swiss Alps to disentangle genetic differentiation and genotype-by-environment interactions underlying trait variation along a steep climatic and edaphic gradient. We measured several functional traits as well as arthropod herbivory and fungal infection prevalence. 3. We found strong evidence for trait differentiation between populations and weaker evidence for genotype-by-environment responses to transplant elevation or soil conditions. Herbivory showed little variation among transplant sites, whereas fungal disease decreased strikingly with increasing elevation and disease also varied according to population origin. Importantly, several traits showing population differentiation were linked to variation in plant consumer damage. 4. Our results suggest that variation in functional traits contribute to variation in plant-consumer interactions. More broadly, this study highlights the usefulness of identifying the sources of trait variation when predicting plant-consumer dynamics under environmental change.