Journal of Chemical Ecology

Due to climate change, extreme weather events such as droughts are becoming more frequent and intense. This has a profound impact on plant performance and ecological interactions, including those involving herbivorous insects. The combined impact of drought stress and insect herbivory on plant metabolism has rarely been studied, particularly in woody plants. In this study, we investigated the influence of varying degrees of drought, both alone and in combination with herbivory by the leaf beetle Chrysomela tremulae, on the morphological and chemical characteristics of black poplar (Populus nigra) trees using a full factorial experimental design. We quantified morphological traits, volatile organic compound (VOC) emissions, phytohormone and amino acid concentrations, and phenolic profiles. Drought conditions increased the concentrations of salicylic acid (SA) and abscisic acid (ABA), while feeding induced ABA and SA. Amino acid profiles shifted significantly under drought conditions, particularly in beetle-infested plants. In contrast, salicinoids, which are the most important phenolic defense compounds in poplars, remained relatively stable. We also observed significant compound-specific effects on both constitutive and herbivore-induced VOC emissions. Our results demonstrate that drought and insect herbivory exert a joint influence on the chemical responses of P. nigra across multiple metabolic pathways. These findings highlight how the interaction between abiotic and biotic stresses can influence the defense chemistry of trees, which will consequently affect ecological interactions in forest ecosystems in the face of climate change.

A growing body of literature proposes that psychoactive plant compounds evolved as defenses against herbivorous insects, with their neurological effects in humans an evolutionary accident of conserved receptor architecture. This hypothesis - which we call the herbivore defense hypothesis - is widely invoked but rarely tested empirically. We report a controlled dietary bioassay in which Spodoptera frugiperda larvae were fed artificial diet incorporating lyophilized kratom (Mitragyna speciosa) leaf powder or purified mitragynine, the primary psychoactive compound in kratom leaf. Kratom leaf caused dose-dependent larval mortality, suppressed growth rates, and reduced pupation rates across all tested concentrations, with near-complete mortality at the highest dose. Purified mitragynine produced modest but significant growth suppression relative to the control, but had no significant effect on survival and was substantially outperformed by whole leaf powder at the same mitragynine-equivalent concentration. Because insects lack the {micro}-opioid receptors through which mitragynine exerts its psychoactive effects in mammals, its insecticidal activity cannot be mediated by the same receptor interaction responsible for its human pharmacology. We use these findings to critically evaluate the herbivore defense hypothesis, and find that its current framing is insufficient to answer one of chemical ecologys most compelling questions: why do plants make compounds that alter the human mind?

O_LIVolatile organic compounds (VOCs) mediate plant-plant signalling and may contribute to phenotypic differentiation among populations. However, the extent to which VOC-mediated signalling varies among locally adapted populations, and how VOC traits relate to major fitness-related traits, remain poorly understood. C_LIO_LIWe conducted a greenhouse experiment using two genetically and phenologically divergent Iberian populations of Arabidopsis thaliana. Plants were exposed to herbivory by Spodoptera exigua, after which we quantified herbivore-induced VOC emissions, VOC-mediated signalling effects on neighbouring conspecifics, and relationships between VOC traits, flowering time, and seed germination. C_LIO_LIHerbivory altered VOC composition, but overall VOC profiles remained broadly similar between populations despite strong divergence in life-history strategies, constitutive resistance to herbivory, and genetic structure. In contrast, correlations between VOC traits and fitness-related traits differed between populations and herbivory treatments. Nevertheless, receiver plants from both populations exhibited reduced herbivore damage after exposure to herbivore-induced emitters, indicating conserved VOC-mediated signalling. C_LIO_LIOur results suggest that herbivore-induced volatile signalling may represent a relatively conserved component of plant defence across locally adapted populations. In contrast, relationships between VOC traits and life-history variation may reflect population-specific integration of defence and fitness-related traits. C_LI

Adult mosquitoes rely on plant-derived sugars for survival, reproduction, and flight, yet the plant taxa that mosquitoes encounter in nature and the odors that make those plants attractive remain poorly understood. Most studies of mosquito attraction to plant odors have focused on candidate plants selected a priori, rather than plants linked to field-collected mosquitoes. Here, we combined plant DNA barcoding, semi-field behavioral assays, and volatile profiling to identify field-associated plant resources relevant to Aedes aegypti. Plant DNA recovered from mosquitoes collected across three Florida counties revealed broad plant associations, including 90 genera spanning 37 families, with several taxa recurring across counties or appearing prominently within particular localities. Behavioral experiments in semi-field sticky-trap assays found that five field-associated plant taxa were significantly attractive relative to blank controls, indicating that taxa associated with mosquitoes in nature can also function as attractive cues under semi-field conditions. GC-MS analyses of headspace collections from 42 plant taxa detected 211 volatile compounds and revealed substantial variation in both total emission rate and odor composition among taxa. Although several compounds, including -pinene, limonene, 4-ethylacetophenone, 2-ethyl-1-hexanol, 4-ethylbenzaldehyde, and caryophyllene, were broadly distributed across plant groups, volatile profiles differed significantly among taxa and shared compounds often occurred at markedly different proportional abundances. The five behaviorally tested taxa likewise showed both overlap and divergence, sharing 17 compounds across all five taxa while differing in dominant constituents and total emissions. Together, these results show that Ae. aegypti interacts with a diverse set of plants in the field, and suggests nectar-seeking is shaped not simply by plant identity or total odor abundance, but by the composition and proportional structure of plant odors.

Pesticides remain indispensable for global food security, yet their use must be reconciled with the preservation of biodiversity. Despite advances in developing safer pesticides, their sublethal effects and synergistic potential with co-formulants in tank-mixtures, including inert spray adjuvants, often remain poorly understood in beneficial insects like bees. In this study, we assessed the effects of acute oral exposure to field-realistic doses of SilwetTM L-77 (an organosilicone adjuvant; 0.1-2.5%), acetamiprid (a cyano-substituted neonicotinoid; 6-150 ng/bee), and sulfoxaflor (a sulfoximine; 3-27 ng/bee) on gustatory responsiveness, associative olfactory learning, and short-term memory retention in honeybees (Apis mellifera L.). While we found no significant evidence of interaction effects at the exposure concentrations tested, the highest doses of SilwetTM L-77 and sulfoxaflor alone significantly reduced gustatory responsiveness. Furthermore, all three agrochemicals alone weakly affected associative learning without impacting memory retention. Although adjuvant-insecticide mixtures did not synergistically impair bee cognition, these adjuvants can impact sensory perception. Moving beyond mortality-based assessments and including sensory-cognitive thresholds is essential for a more holistic understanding of pollinator health.

1. Since plants interact with their environment through complex combinations of phytochemicals rather than metabolites in isolation, quantifying plant chemodiversity is of increasing interest. Although functionally relevant, structural disparity is mostly neglected in measures of chemodiversity because its integration relies on known compound identity, limiting broad application. 2. We established an approach deriving compound dissimilarity from UV-Vis spectra in HPLC-DAD datasets, evaluated how it relates to structure- or biosynthesis-based approaches, and examined whether it provides meaningful contributions to chemodiversity measures. For this, we applied it in an experiment full-factorially testing the effects of drought and herbivory on Solanum dulcamara leaf chemodiversity. 3. UV-Vis spectral dissimilarity aligned well with fMCS-based structural dissimilarity and reflected structural relationships within a set of standards. Incorporating it into chemodiversity analysis improved separation of the effects of drought and herbivory. Especially in the combination of both stresses, their distinct effects on different leaf metabolites were only fully reflected when accounting for compound disparity. 4. Hence, UV-Vis spectral dissimilarity captures chemically meaningful compound relatedness without requiring compound identity. Using it as a proxy for compound disparity adds a biologically relevant dimension to measures of chemodiversity with broader implications when assessing functional consequences of phytochemical diversity.

O_LIEuropean beech (Fagus sylvatica L.) is a widely distributed, ecologically and economically important deciduous tree species in European forests, but is increasingly threatened by drought stress. Volatile organic compounds (VOCs) are ubiquitous plant metabolites that may serve as non-invasive biomarkers of drought stress, yet they have rarely been studied in European beech. C_LIO_LIIn this study, we examined VOC responses of European beech to experimental drought across diverse genetic backgrounds in a common garden. The 72 four-year-old beech saplings represented three genetic clusters, seven provenances (geographic seed sources), and 12 maternal seed families. Half of the saplings were assigned to the drought treatment and received no water for 14 days, while the remaining saplings served as controls and were watered as required. VOC profiles, quantified as peak heights of mass spectral features, were measured for all individuals during pre-drought, drought, and rewatering periods. C_LIO_LIWe found that pre-drought VOC profiles, in particular monoterpenes, varied significantly among genetic backgrounds. Experimental drought significantly altered VOC profiles, characterized by increased green leaf volatiles and decreased monoterpenes, oxidized terpenoid derivatives, and other fatty acid derivatives. Reductions in monoterpenes persisted after rewatering, indicating a drought legacy effect. Drought responses were largely conserved across genetic backgrounds, with significant seed family-specific responses detected for only three VOC features. C_LIO_LIOur findings suggest that VOC profiles are genetically structured yet highly plastic under drought and highlight their potential as non-invasive biomarkers for monitoring drought stress in European beech under climate change. C_LI

Volatile organic compounds (VOCs) define the distinctive aroma of cannabis and critically influence consumer preference, cultivar authentication, and breeding programs. However, systematic characterization of VOC diversity across commercial drug-type cultivars remains limited. This study presents a comprehensive volatilomics-based phenotypic characterization of 165 commercial drug-type cannabis accessions using gas chromatography with flame ionization detection and mass spectrometry (GC-FID/MS). We identified 61 high-confidence VOCs assigned to three biosynthetic classes: terpenoids (n = 45), fatty acid-derived volatiles (n = 12) and amino acid-derived volatiles (n = 4), resolved into 12 subclasses. Analysis of variance revealed highly significant among-accession differences for all compounds (p < 0.001; 2 = 0.67-0.97), with repeatability estimates averaging 0.81 (range 0.50-0.95). Unsupervised clustering partitioned accessions into three distinct chemotypes (n = 90, 53, and 22), supported by principal component and t-SNE analyses. Machine learning-based feature selection identified a consensus panel of 12 discriminative compounds (camphene, -fenchene, sabinene, -terpinene, ({+/-})-limonene, -humulene, linalool, endo-fenchol, {Delta}3-carene, -thujene, {gamma}-terpinene and -phellandrene) that recovered the chemotype assignment of 32 of 33 held-out accessions. Estimated odor-activity screening ranked prenylthiol, -pinene, ({+/-})-limonene, linalool and myrcene highest among the odor-active compounds. All three chemotypes shared a prenylthiol-dominated core (67-77% of summed OAV) and were distinguished by the extent and nature of terpenoid modulation of that core: minimally modulated (Cluster ZERO), citrus-floral modulated (Cluster ONE) and pine-terpenic modulated (Cluster TWO). These findings indicate that volatile diversity in this panel can be summarized by three reproducible chemotypes, providing a quantitative basis for accession characterization and a foundation for future breeding and quality-assessment studies.

Plant-parasitic nematodes (PPNs) are among the most destructive agricultural pests worldwide, causing significant economic losses across diverse cropping systems. Soil fumigation, the most common management strategy, is costly, detrimental to soil health, and increasingly restricted due to environmental and regulatory concerns. As a result, there is a critical need for alternative, sustainable approaches for PPN control. Solanum sisymbriifolium is resistant to several Meloidogyne species and represents a promising source of natural nematicidal compounds. In this study, we evaluated the effects of S. sisymbriifolium extracts on Meloidogyne chitwoodi and M. hapla, two economically important nematodes. Compounds were extracted using solvents of increasing polarity and then reconstituted in water. The water-solubilized extracts were then used in bioassays to assess their effects on nematode egg hatching, egg viability, and second-stage juvenile (J2) survival. Egg hatching and J2 viability of both Meloidogyne species were consistently affected by compounds in the 1-butanol fraction. Further characterization of these compounds may enable the development of novel, environmentally sustainable alternatives to conventional nematode management strategies.

Antimicrobial resistance represents a continuing threat to clinical infection management, with methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Escherichia coli identified by the World Health Organization as priority pathogens. This study evaluated the antimicrobial activity, synergistic potential, and chemical composition of six plant-derived preparations (three ethanolic extracts: nettle, thyme, rosemary; and three essential oils: lavender, lemongrass, doTERRA Peace blend) against MRSA, methicillin-sensitive S. aureus (MSSA), and E. coli K-12 by disc diffusion, broth microdilution, post-exposure culturability, antimicrobial interactions assessed by checkerboard assay, and GC-MS profiling. Disc diffusion produced no interpretable zones of inhibition for any plant preparation tested; however, broth microdilution revealed reproducible inhibitory activity within published ranges across the panel. Three essential oils achieved a median Minimum Inhibitory Concentration (MIC) of 0.39 mg/mL against MRSA despite presenting compositionally distinct chemotypes: lavender was linalool-dominated (61% combined), lemongrass was citral-dominated (76%), and the doTERRA blend was sesquiterpene-rich. Rosemary ethanolic extract achieved the same potency (0.39 mg/mL) against MSSA. No preparation produced a bactericidal reduction (>=3 log10 CFU/mL) at any timepoint, with all reductions transient and recovering by 24 hours. Checkerboard combinations of plant preparations with vancomycin and ciprofloxacin were uniformly classified, according to the Fractional Inhibitory Concentration Index (FICI), as indifference/no interaction, attributable in part to inoculum-mediated effects on vancomycin MIC. To analyse the relationship between chemical composition and antimicrobial outcomes, we introduce a Chemotype Similarity Index (CSI), a chemometric framework quantifying pairwise compositional similarity between essential oils by Pearson correlation and relating it to log2-MIC differences across strains. CSI revealed a strain-dependent chemistry-activity relationship, convergent against MRSA, monotonic against MSSA, and absent against E. coli, indicating that compositional similarity predicts antimicrobial outcomes on a strain-specific basis. The convergence of three chemotypically divergent essential oils with the same anti-MRSA potency suggested a shared membrane-disrupting mechanism operating through distinct chemical routes. Although exploratory at this scale, the CSI framework provides a reusable analytical scaffold for linking phytochemical composition to antimicrobial activity, and identifies the MRSA convergence as a specific direction for mechanistic investigation into the development of plant-derived antimicrobial adjuncts.

The generalist Helicoverpa armigera and the specialist Helicoverpa assulta are closely related noctuid pests and are among the few insect herbivores capable of feeding on and damaging hot pepper fruits, which contain the defensive compound capsaicin. Cytochrome P450 monooxygenases (P450s) contribute to the metabolism of plant defensive compounds and can facilitate insect adaptation to chemically defended host plants. Here, we identified CYP6AN1 in H. assulta (HassCYP6AN1) and comparatively characterized the CYP6AN1 orthologs from H. armigera (HarmCYP6AN1) and H. assulta. RACE identified one full-length HarmCYP6AN1 transcript and three full-length HassCYP6AN1 transcript isoforms. The HassCYP6AN1 isoforms contained distinct 5' UTRs generated by alternative transcription initiation and splicing but shared an identical coding sequence. Sequence comparisons and phylogenetic analysis supported their assignment as orthologs. Constitutive CYP6AN1 expression was higher in the H. assulta midgut, whereas dietary capsaicin significantly induced CYP6AN1 expression in the H. armigera midgut. Recombinant CYP6AN1 proteins were co-expressed with NADPH-cytochrome P450 reductase in Escherichia coli, and their substrate-metabolizing activities were evaluated using HPLC-based depletion assays. Both orthologs metabolized capsaicin, but HarmCYP6AN1 exhibited an approximately 2.3-fold higher depletion activity than HassCYP6AN1 under the conditions tested. HarmCYP6AN1 also showed P450-content-dependent xanthotoxin depletion, whereas no detectable xanthotoxin metabolism was observed for HassCYP6AN1. These findings establish CYP6AN1 as a component of the capsaicin-metabolizing repertoire of both species and reveal substantial divergence between the orthologs in transcript organization, expression regulation, catalytic activity, and detectable substrate range.

Here, oyster larval developmental abnormalities within a New England hatchery were linked to a common UV sterilization technique that has been used for over 20 years. Because of the known link between phytoplankton oxylipins and egg mortality in copepods, we hypothesized that UV pretreatment of seawater results in the production of oxylipins that inhibit larval digestion of microalgae. We used lipidomics to observe changes in the organic compounds dissolved in estuarine seawater when filtered and when filtered and pretreated with UV. UV treatment resulted in an increase in the relative abundance of oxylipins associated with cyanobacteria, fungi, and macroalgae in 2020, whereas oxylipins typically produced by diatoms were more abundant in the UV treatments from 2021. Oxylipin concentrations were higher in 2020, when the hatchery reported the most severe problems with larval development. Removing the UV step allowed continued larval production in both years. However, the lack of UV sterilization led to an unidentified bacterial pathogen in 2021, which nearly decimated the overall seasonal production of oyster seed. To follow up in a more controlled environment, the larvae were exposed to exogenous oxidized lipids, which resulted in the same digestive syndrome and histological symptoms as the endogenous suite of compounds produced by UV. Further investigation of the lipidomes revealed that oxylipins were only one class of potentially harmful compounds linked to UV sterilization, and the dissolved concentrations of secondary metabolites associated with higher plants, a wide range of pharmaceuticals, and anthropogenic organic pollutants also increased under UV light. Future efforts will explore the sources of these compounds, the mechanisms by which they inhibit oysters, and whether this is an emerging environmental problem for other ecosystems and shellfish hatcheries. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=137 SRC="FIGDIR/small/738347v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@43d06corg.highwire.dtl.DTLVardef@2894daorg.highwire.dtl.DTLVardef@449e59org.highwire.dtl.DTLVardef@f81983_HPS_FORMAT_FIGEXP M_FIG C_FIG

Tropospheric ozone (O) is a major atmospheric pollutant that affects plant carbon metabolism, redox homeostasis, and secondary metabolism, including the biosynthesis and emission of biogenic volatile organic compounds (BVOCs). However, the contribution of BVOCs to O3 tolerance, particularly in tropical woody species, remains poorly understood. Here, we investigated whether acute O exposure (cumulative AOT40 of 3497.82 ppb h) induces alterations in photosynthetic performance, redox homeostasis, and BVOC partitioning in Eugenia uniflora. We evaluated gas exchange, photosynthetic pigments, ascorbate and glutathione pools, emitted BVOCs, modeled intercellular BVOC concentrations, and the relative carbon cost associated with BVOC emissions. O exposure significantly increased net CO2 assimilation without affecting stomatal conductance, transpiration, leaf water status, or chlorophyll concentrations, indicating maintenance of photosynthetic performance. Carotenoid concentrations and total glutathione decreased, whereas glutathione redox status was maintained. O induced marked compound-specific changes in BVOC composition and partitioning. Several monoterpenes appeared exclusively under O exposure, {gamma}-elemene emission increased significantly, and the relative distribution of individual BVOCs between the modeled intercellular and emitted pools was altered. These findings show that the response of E. uniflora to acute O exposure was characterized by interplay among carbon assimilation, glutathione redox regulation, and BVOC partitioning rather than by increased total volatile emission. Enhanced carbon assimilation occurred without additional carbon loss through BVOC release, while changes in the modeled intercellular pool indicate that part of the volatile response remained within the leaf. Our findings highlight BVOC partitioning as an important dimension of the plant response to oxidative stress and demonstrate that emission measurements alone may not fully capture the fate and potential physiological role of volatile carbon under O exposure. O_FIG O_LINKSMALLFIG WIDTH=178 HEIGHT=200 SRC="FIGDIR/small/743946v1_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@653af1org.highwire.dtl.DTLVardef@ca5forg.highwire.dtl.DTLVardef@1e641bforg.highwire.dtl.DTLVardef@1e68fae_HPS_FORMAT_FIGEXP M_FIG C_FIG BVOC Partitioning Contributes to Oxidative Stress Defence Under Acute O Exposure

Barley yellow dwarf virus (BYDV), transmitted by the bird cherry-oat aphid (Rhopalosiphum padi L.), is among the most damaging viral diseases of barley, but the mechanisms underlying resistance to both the virus and its vector remain poorly understood. Here, we investigated resistance associated with the Hordeum bulbosum-derived Ryd4 introgression in the barley hybrid SY Kestrel by integrating behavioural, electrophysiological, physiological and multi-omics analyses with functional validation of defence metabolites. SY Kestrel exhibited constitutive volatile-mediated antixenosis together with strong post-settlement antibiosis characterised by impaired phloem feeding, reduced aphid fitness and suppression of BYDV gene expression 10 days after transmission. Integrated transcriptomic, metabolomic and small RNA analyses revealed coordinated immune activation, chloroplast remodelling and defence metabolism associated with the resistance introgression. Candidate immune regulators were identified both within the refined Ryd4 interval and the surrounding introgressed region. Maintenance of photosystem II function was accompanied by reprogramming of -linolenic acid-derived oxylipin metabolism, while phenylpropanoid and branched-chain amino acid/lysine pathways generated metabolites that directly reduced aphid survival. We demonstrate that the Ryd4 introgression coordinates constitutive vector deterrence with host defence reprogramming to restrict aphid colonisation and suppress BYDV establishment. These results provide a mechanistic framework for improving durable resistance to aphid-transmitted viruses in cereals.

Herbicide resistance threatens effective weed control in modern agriculture, particularly in grass weeds such as Alopecurus myosuroides and Lolium multiflorum. Cinmethylin is a pre-emergence herbicide with a novel mode of action that inhibits plastidial fatty acid thioesterases (FATs), enzymes essential for fatty acid biosynthesis. Although no cases of field resistance to cinmethylin have been reported, its resistance risk has not been fully assessed. In this study, we biochemically characterized defined amino acid substitutions in FAT A and FAT B to evaluate their effects on cinmethylin inhibition profile. Some substitutions in FAT A reduced inhibition in vitro, with mutations at residue R171 causing the largest shifts in sensitivity. However, these highly resistant variants required multiple specific nucleotide polymorphisms and are therefore predicted to be unlikely to arise in weed populations. In FAT B, sensitivity shifts were generally moderate. Importantly, most substitutions that reduced cinmethylin sensitivity also impaired enzymatic activity, suggesting limited viability in planta. Overall, these results indicate that while theoretical target-site resistance mechanisms exist, the practical risk of rapid resistance evolution to cinmethylin is low, supporting its value for integrated grass weed management

Bisphenol S (BPS), a widely used substitute for bisphenol A, is increasingly detected in aquatic environments; however, its neurodevelopmental effects remain insufficiently understood. This study investigated whether developmental exposure to an environmentally relevant concentration of BPS disrupts social behaviour and underlying neurobiological pathways in zebrafish (Danio rerio). At 21 days post-fertilization, BPS-exposed larvae exhibited a significant reduction in social preference, indicating impaired conspecific interactions. Neurochemical analysis revealed a marked increase in serotonin (5-HT) levels, whereas lipid peroxidation (MDA) remained unchanged, suggesting the absence of overt oxidative damage. Gene expression profiling demonstrated a dysregulated antioxidant response, suppression of apoptotic signaling, and pronounced upregulation of serotonergic receptors and transporters. To resolve system-level mechanisms, protein-protein interaction (PPI) network analysis identified BDNF and CREB1 as dominant regulatory hubs, with the serotonergic synapse pathway as the most significantly enriched term. Molecular docking further demonstrated direct binding of BPS to multiple serotonergic targets, including HTR1A and TPH2, supporting receptor-level interference. Expanded network and pathway analyses revealed coordinated enrichment of monoamine GPCR, oxidative stress, and inflammatory pathways. These findings demonstrate that BPS induces serotonergic dysregulation and network-level reprogramming rather than significant oxidative damage, leading to behavioural impairment. This study provides a multi-scale mechanistic framework linking molecular perturbations to neurobehavioural outcomes, identifying serotonergic signaling and BDNF-CREB1 pathways as central targets of BPS neurotoxicity.

Nectar is a primary floral reward, which can also deter non-specialist pollinators; yet, the role of complex nectar composition in plant-pollinator interactions and its relationship to other floral traits remain understudied, particularly in natural communities. We profiled the nectar metabolome of 43 co-occurring species in an alpine grassland to evaluate relationships among nectar chemistry, phylogeny, floral display traits and pollinator visitation. Field observations revealed a dominant bee vs fly visitation gradient. Several aggregated nectar traits tracked this gradient independently of plant phylogeny, indicating functional convergence: specifically, bee visitation was associated with higher nectar sucrose proportion, greater compound richness, and more divergent profiles of uncommon sugars. Nectar traits exhibited variable relationships to floral display traits, suggesting partial inter-trait phenotypic integration. Together, these findings indicate that detailed features of nectar composition, including phytochemical diversity, play a functional role in floral phenotypes, with previously unappreciated implications for plant-pollinator community ecology.

Veterinary ectoparasiticides widely used on companion animals often contain synthetic insecticides whose agricultural applications have been restricted in the European Union because of environmental concerns. These neurotoxic compounds can persist on animal fur and enter surrounding environments, potentially exposing non-target organisms. The Great Tit (Parus major), a common passerine in both urban and forest habitats, frequently incorporates animal fur in nest linings, thereby creating a potential exposure route for breeding adults and nestlings. We analysed fur-containing nest material collected from 63 Great Tit nests in artificial nest boxes at an urban site and a nearby protected forest in Hungary during the 2025 breeding season, sampling at mid-nestling stage and also after fledging. Using HPLC-MS/MS and GC-MS, we detected several veterinary ectoparasiticides in nest materials, including fipronil, fipronil sulfone, imidacloprid, and permethrin. Acetamiprid was found only in urban nests, indicating additional, non-veterinary environmental sources. Multiple insecticides were present in nest material, with higher contamination levels and greater compound diversity in urban compared to forest nests. Residues were present at both sampling times but declined over the course of the breeding cycle. Although contamination was not associated with the measured reproductive parameters of Great Tits, our findings show that veterinary ectoparasiticides can contaminate wild bird nests, including those in protected forest ecosystems. This highlights a previously under-recognised pathway linking companion animal treatments to wildlife exposure and underscores the need to assess the ecological risks and trade-offs associated with widespread veterinary insecticide use. HighlightsO_LIVeterinary ectoparasiticides were detected in urban and forest Great Tit nests C_LIO_LIUrban nests contained higher contamination levels and greater compound diversity C_LIO_LIAcetamiprid occurred only in urban nests, indicating additional environmental inputs C_LIO_LIProtected forests also exposed to fipronil, fipronil sulfone and permethrin C_LIO_LIBird nests reveal an overlooked pathway linking pet treatments to wildlife exposure C_LI

Nutrition plays a fundamental role in insect physiology, yet whether growth, immunity and stress responses share a common nutritional optimum remains poorly understood. Using the Geometric Framework for Nutrition, we investigated how dietary protein and carbohydrate balance regulate multiple physiological functions in the specialist herbivore Plutella xylostella. Growth was jointly determined by protein and carbohydrate intake, with maximal biomass accumulation constrained primarily by protein availability. Immune traits showed distinct nutritional optima: total hemocyte counts and phenoloxidase activity were maximised at intermediate protein-carbohydrate (P:C) ratios, whereas survival following Bacillus thuringiensis challenge depended predominantly on protein intake. Antioxidant and detoxification responses likewise varied non-linearly across the nutrient landscape, with individual enzyme systems each exhibiting distinct nutrient-dependent optima. Importantly, no single macronutrient balance simultaneously maximised growth, immune performance and oxidative homeostasis, demonstrating that these functions have divergent nutritional requirements. Together, these findings show that macronutrient balance generates competing physiological demands, offering an integrated view of nutrient-dependent regulation of growth, immunity and stress physiology in a specialist herbivore.

The multivoltine non-native box tree moth, Cydalima perspectalis (Lepidoptera: Crambidae), was accidentally introduced in several continents and exhibited a very rapid expansion in its invaded ranges, colonising around 40 countries in less than twenty years. Initially observed in urban areas, it quickly spread to forest stands, causing significant damage to boxwood trees. If the role of the ornamental plant trade in its fast invasion has been investigated, the insects flight capabilities has thus far been overlooked, limiting estimations of its natural dispersal. In this context, we assessed the flight performance of the adults and investigated potential effects of sex, age and generation using computer-monitored flight mills. Under these controled conditions, we estimated the distance flown per night and over the adults lifespan in both sexes for each generation. The adults were able to fly on average 18 km within their lifespan, even though distances flown were highly variable, including several females capable of performing long-distance flights (up to 150 km). The distances covered were partly correlated with the age and body mass of the adults. Mated females flew longer distances than virgin ones, but long dispersal seemed to limit their fecundity. Finally, the overwintering generation presented the highest flight capabilities with individuals able to cover 22 km on average while the late summer generation covered only 10 km. The box tree moth showed good dispersal abilities that likely played a significant role in its rapid local expansion, while human-mediated dispersal favoured its long-distance dispersal.