Consequences of climate warming and altered precipitation patterns for plant-insect and multitrophic interactions

Interactive Effects of Temperature, Aridity, and Plant Stoichiometry on Insect Herbivory: Past and Present

AbstractThe influence of climate on deep-time plant-insect interactions is becoming increasingly well known, with temperature, CO2 increases (and associated stoichiometric changes in plants), and aridity likely playing a critical role. In our modern climate, all three factors are shifting at an unprecedented rate, with uncertain consequences for biodiversity. To investigate effects of temperature, stoichiometry (specifically that of nitrogen), and aridity on insect herbivory, we explored insect herbivory in three modern floral assemblages and in 39 fossil floras, especially focusing on eight floras around a past hyperthermal event (the Paleocene-Eocene Thermal Maximum) from Bighorn Basin (BB). We find that higher temperatures were associated with increased herbivory in the past, especially among BB sites. In these BB sites, non-N2-fixing plants experienced a lower richness but higher frequency of herbivory damage than N2-fixing plants. Herbivory frequency but not richness was greater in BB sites compared with contemporaneous, nearby, but less arid sites from Hanna Basin. Compared with deep-time environments, herbivory frequency and richness are higher in modern sites, suggesting that current accelerated warming uniquely impacts plant-insect interactions. Overall, our work addresses multiple aspects of climate change using fossil data while also contextualizing the impact of modern anthropogenic change on Earth's most diverse interactions.

Heatwaves exacerbate pollen limitation through reductions in pollen production and pollen vigour

Increasingly frequent heat waves threaten the reproduction of flowering plants; compromising the future persistence, adaptive capacity, and dispersal of wild plant populations, and also the yield of fruit-bearing crop plants. Heat damages the development of sensitive floral organs and gametes, which inhibits pollen germination, pollen tube growth, and fertilization. However, the role of heat has not been integrated into the framework of pollen quantity and quality limitation and how heat influences the success of cross and self-pollination. We exposed developing flowers to either controlled temperature (25 °C:20 °C) or extreme heat (35 °C:20 °C) over 72 h. We then hand-pollinated them with either crossed or self-derived pollen from the same temperature treatment to determine the direct and interactive effects of simulated heatwaves on pollen tube growth and resulting seed set. We also collected anthers from virgin flowers to measure heat impacts on pollen production. Under cooler control temperatures pollen tube survival of self-derived pollen was approximately 27% lower than that of crossed pollen. Pollen tube survival in heat-treated cross-pollinated and heat-treated self-pollinated flowers were 71% and 77% lower compared to flowers cross-pollinated at control temperatures. These differences in pollen tube survival rate between heat-treated cross-pollinated and heat-treated self-pollinated flowers were insignificant. Furthermore, extreme heat reduced seed set by 87%, regardless of pollen origin, and also reduced pollen production during flower development by approximately 20%. Our results suggest flowers that develop during heatwaves are likely to experience exacerbated pollen quantity and quality limitation driven by changes in pollen production and pollen vigour. Heatwave-induced pollen limitation will likely reduce crop yields in agricultural systems, and depress mating and reproduction in wild plant species, the latter of which may hinder the adaptive capacity of plants to a rapidly changing world.

Effect of Olive Fruit Volatiles on Landing, Egg Production, and Longevity of Bactrocera oleae Females under Different Temperatures

Females of the olive fruit fly Bactrocera oleae use various contact and volatile plant stimuli to find olive fruits and lay their eggs on them. We detected certain volatile organic compounds (VOCs) emitted from the olive fruit and studied their effect on female landings on olive fruits, egg production, and longevity under a series of different temperatures from 15 °C to 35 °C. When female flies were maintained at temperatures from 17 °C to 30 °C and exposed to different fruit VOCs either increased or decreased, depending on the substance tested, their landings on olives, egg production, and longevity. Temperature significantly affected the females' responses to fruit VOCs. The highest responses of the flies to fruit VOCs were observed at 30 °C, except for longevity. By contrast, at 15 °C or 35 °C, the flies did not show any response to VOCs. Our results may contribute to a better understanding of the olive fly positive or negative responses to fruit VOCs and the improvement of its control.

Predicted community consequences of spatially explicit global change-induced processes on plant-insect networks

Plant-insect trophic systems should be particularly sensitive to processes altering species spatial co-occurrences, as impacts on one level can cascade effectively through the strong trophic reliance to the other level. Here, we predicted the biogeography of Lepidoptera-plant communities under global-change scenarios, exploiting spatially resolved data on 423 Lepidoptera species and their 848 food plants across the German state of Baden-Württemberg (ca. 36,000 km2). We performed simulations of plant extinction and Lepidoptera expansion, and respectively assessed their cascading consequences-namely secondary extinction of Lepidoptera and change in functional distance of plants-on the interaction networks. Importantly, the simulations were spatially explicit, as we accounted for realistic landscape contexts of both processes: Plant extinctions were simulated as "regional" (a species goes extinct in the whole region at once) vs. "isolation-driven" (a species gradually goes extinct from the peripheral or isolated localities according to its real regional distribution); Lepidoptera expansions were simulated with random, northward, and upward directions according to real topography. The consequences were assessed based on empirical community composition and trophic relationships. When evaluated by regional richness, the robustness of Lepidoptera assemblages against secondary extinctions was higher under isolation-driven plant extinctions than regional plant extinction; however, this relationship was reversed when evaluated by averaged local richness. Also, with isolation-driven plant extinctions, Lepidoptera at the central sub-region of Baden-Württemberg appeared to be especially vulnerable. With Lepidoptera expansions, plants' functional distances in local communities dropped, indicating a possible increase of competition among plants, yet to a lesser extent particularly with upward movements. Together, our results suggested that the communities' composition context at the landscape scale (i.e., how communities, with respective species composition, are arranged within the landscape) matters when assessing global-change influences on interaction systems; spatially explicit consideration of such context can reveal localised consequences that are not necessarily captured via a spatially implicit, regional perspective.

Water temperature governs organophosphate ester dynamics in the aquatic food chain of Poyang Lake

Organophosphate esters (OPEs) are increasingly recognized as pervasive environmental contaminants, primarily from their extensive application in flame retardants and plasticizers. Despite their widespread presence, the intricacies of OPE bioaccumulation within aquatic ecosystems remain poorly understood, particularly the environmental determinants influencing their distribution and the bioaccumulation dynamics across aquatic food chains. Here we show that water temperature plays a crucial role in modulating the dispersion of OPE in the aquatic environment of Poyang Lake. We quantified OPE concentrations across various matrices, uncovering levels ranging from 0.198 to 912.622 ng L-1 in water, 0.013-493.36 ng per g dry weight (dw) in sediment, 0.026-41.92 ng per g wet weight (ww) in plankton, 0.13-2100.72 ng per g dw in benthic invertebrates, and 0.31-3956.49 ng per g dw in wild fish, highlighting a pronounced bioaccumulation gradient. Notably, the intestines emerged as the principal site for OPE absorption, displaying the highest concentrations among the seven tissues examined. Among the various OPEs, tris(chloroethyl) phosphate was distinguished by its significant bioaccumulation potential within the aquatic food web, suggesting a need for heightened scrutiny. The propensity for OPE accumulation was markedly higher in benthic invertebrates than wild fish, indicating a differential vulnerability within aquatic biota. This study lays a foundational basis for the risk assessment of OPEs as emerging contaminants and underscores the imperative to prioritize the examination of bioaccumulation effects, particularly in benthic invertebrates, to inform future environmental safeguarding strategies.

Heat stress reprograms herbivory-induced defense responses in potato plants

Climate change is predicted to increase the occurrence of extreme weather events such as heatwaves, which may thereby impact the outcome of plant-herbivore interactions. While elevated temperature is known to directly affect herbivore growth, it remains largely unclear if it indirectly influences herbivore performance by affecting the host plant they feed on. In this study, we investigated how transient exposure to high temperature influences plant herbivory-induced defenses at the transcript and metabolic level. To this end, we studied the interaction between potato (Solanum tuberosum) plants and the larvae of the potato tuber moth (Phthorimaea operculella) under different temperature regimes. We found that P. operculella larvae grew heavier on leaves co-stressed by high temperature and insect herbivory than on leaves pre-stressed by herbivory alone. We also observed that high temperature treatments altered phylotranscriptomic patterns upon herbivory, which changed from an evolutionary hourglass pattern, in which transcriptomic responses at early and late time points after elicitation are more variable than the ones in the middle, to a vase pattern. Specifically, transcripts of many herbivory-induced genes in the early and late defense stage were suppressed by HT treatment, whereas those in the intermediate stage peaked earlier. Additionally, we observed that high temperature impaired the induction of jasmonates and defense compounds upon herbivory. Moreover, using jasmonate-reduced (JA-reduced, irAOC) and -elevated (JA-Ile-elevated, irCYP94B3s) potato plants, we showed that high temperature suppresses JA signaling mediated plant-induced defense to herbivore attack. Thus, our study provides evidences on how temperature reprograms plant-induced defense to herbivores.

Variations in water use efficiency and carbon and nitrogen concentrations in red heart Chinese fir

Temperature can significantly (P < 0.05) affect plant growth by modifying water use strategies, which are determined by intrinsic water use efficiency (WUEi). Red Heart Chinese Fir (Cunninghamia lanceolata) is one of the most important ecological and economic plantation species in China. However, the C. lanceolata water use strategy in response to increased temperatures and uneven temporal distribution of precipitation during the growing season is rarely reported. In a 7-year-old C. lanceolata plantation, differences in WUEi and C and N concentrations in different organs were analysed by anova, and the δ13C stable isotope, C, and N concentrations in stems determined at different tree heights. Stepwise regression and variance inflation factor were used to remove autocorrelated factors, and structural equation modelling was then used to explore relationships between WUEi and climate and biological factors. WUEi differed significantly between leaf and branch at different standardized precipitation evapotranspiration indices (SPEI). WUEi and N concentration decreased with age. The highest WUEi in branches and leaves were 92.7 and 88.4 μmol·mol-1 in 2020 (SPEI = 0.00), respectively. δ13C increased with relative tree height but N concentration and C/N ratio were not affected. Air temperatures has increased in between 2014 and 2020. WUEi and N concentration decreased with increasing branch and leaf age, but C concentration increased. SPEI significantly positively affected WUEi (P < 0.05), and WUEi was significantly negatively related to C concentration, which is consistent with the trade-off between C and water.

Global insect herbivory and its response to climate change

Herbivorous insects consume a large proportion of the energy flow in terrestrial ecosystems and play a major role in the dynamics of plant populations and communities. However, high-resolution, quantitative predictions of the global patterns of insect herbivory and their potential underlying drivers remain elusive. Here, we compiled and analyzed a dataset consisting of 9,682 records of the severity of insect herbivory from across natural communities worldwide to quantify its global patterns and environmental determinants. Global mapping revealed strong spatial variation in insect herbivory at the global scale, showing that insect herbivory did not significantly vary with latitude for herbaceous plants but increased with latitude for woody plants. We found that the cation-exchange capacity in soil was a main predictor of levels of herbivory on herbaceous plants, while climate largely determined herbivory on woody plants. We next used well-established scenarios for future climate change to forecast how spatial patterns of insect herbivory may be expected to change with climate change across the world. We project that herbivore pressure will intensify on herbaceous plants worldwide but would likely only increase in certain biomes (e.g., northern coniferous forests) for woody plants. Our assessment provides quantitative evidence of how environmental conditions shape the spatial pattern of insect herbivory, which enables a more accurate prediction of the vulnerabilities of plant communities and ecosystem functions in the Anthropocene.

Predicting global geographical distribution and latitudinal suitability gradient for light Brown apple moth

Epiphyas postvittana, commonly known as the light brown apple moth (LBAM), is native to Australia and has a restricted global distribution. Its polyphagous nature and the recent surge in interceptions have emphasized the need for focused risk assessments to guide effective measures to curb the entry of this pest into new countries. This study aimed to perform a detailed global invasion risk assessment using an optimized MaxEnt model that incorporated 19 bioclimatic variables and elevation. The predictive outcomes underscored the significance of key variables, specifically the minimum temperature of the coldest month (bio6), precipitation of the driest month (bio14), and precipitation of the coldest quarter (bio19), in shaping the potential geographical distribution of LBAM. Regions beyond the existing range, including the southeastern United States, southern Brazil, eastern Argentina, Uruguay, southern Chile, and various Western European countries, were identified as susceptible to invasion and establishment by LBAM. An increase in suitability was observed above 45°N and 40°S under future climate scenario. With respect to climate change, LBAM would expand its potential range in Western Europe and the United States, especially under SSP5-8.5, in the 2050s. An upward trend in the latitudinal suitability gradient for LBAM in mid-high latitude areas implies that amid changing climate conditions, LBAM may find favorable habitats in these regions. For countries and regions with invasion risk, it is imperative to implement corresponding inspections and quarantine measures to thwart the introduction of LBAM, particularly in countries with established trade ties with invaded regions.

Primary Metabolic Response of Aristolochia contorta to Simulated Specialist Herbivory under Elevated CO2 Conditions

This study explores how elevated carbon dioxide (CO2) levels affects the growth and defense mechanisms of plants. We focused on Aristolochia contorta Bunge (Aristolochiaceae), a wild plant that exhibits growth reduction under elevated CO2 in the previous study. The plant has Sericinus montela Gray (Papilionidae) as a specialist herbivore. By analyzing primary metabolites, understanding both the growth and defense response of plants to herbivory under elevated CO2 conditions is possible. The experiment was conducted across four groups, combining two CO2 concentration conditions (ambient CO2 and elevated CO2) with two herbivory conditions (herbivory treated and untreated). Although many plants exhibit increased growth under elevated CO2 levels, A. contorta exhibited reduced growth with lower height, dry weight, and total leaf area. Under herbivory, A. contorta triggered both localized and systemic responses. More primary metabolites exhibited significant differences due to herbivory treatment in systemic tissue than local leaves that herbivory was directly treated. Herbivory under elevated CO2 level triggered more significant responses in primary metabolites (17 metabolites) than herbivory under ambient CO2 conditions (five metabolites). Several defense-related metabolites exhibited higher concentrations in the roots and lower concentrations in the leaves in response to the herbivory treatment in the elevated CO2 group. This suggests a potential intensification of defensive responses in the underground parts of the plant under elevated CO2 levels. Our findings underscore the importance of considering both abiotic and biotic factors in understanding plant responses to environmental changes. The adaptive strategies of A. contorta suggest a complex response mechanism to elevated CO2 and herbivory pressures.

Does spatial variation in insect herbivory match variations in plant quality? A meta-analysis

Variation in herbivore pressure has often been predicted from patterns in plant traits considered as antiherbivore defences. Here, we tested whether spatial variation in field insect herbivory is associated with the variation in plant quality by conducting a meta-analysis of 223 correlation coefficients between herbivory levels and the expression of selected plant traits. We found no overall correlation between herbivory and either concentrations of plant secondary metabolites or values of physical leaf traits. This result was due to both the large number of low correlations and the opposing directions of high correlations in individual studies. Field herbivory demonstrated a significant association only with nitrogen: herbivore pressure increased with an increase in nitrogen concentration in plant tissues. Thus, our meta-analysis does not support either theoretical prediction, i.e., that plants possess high antiherbivore defences in localities with high herbivore pressure or that herbivory is low in localities where plant defences are high. We conclude that information about putative plant defences is insufficient to predict plant losses to insects in field conditions and that the only bottom-up factor shaping spatial variation in insect herbivory is plant nutritive value. Our findings stress the need to improve a theory linking plant putative defences and herbivory.

Sub-optimal temperatures lead to altered expression of stress-related genes and increased 'Candidatus Liberibacter solanacearum' accumulation in potato psyllid

Introduction

The potato psyllid Bactericera cockerelli is the insect vector of the fastidious bacterium 'Candidatus Liberibacter solanacearum'. The bacterium infects both B. cockerelli and plant species, causing zebra chip (ZC) disease of potato and vein-greening disease of tomato. Temperatures are known to influence the initiation and progression of disease symptom in the host plant, and seasonal transitions from moderate to high temperatures trigger psyllid dispersal migration to facilitate survival.

Methods

'Ca. L. solanacearum' -infected and uninfected psyllids were reared at previously established 'permissible', optimal, and 'non-permissible' and temperatures of 18°C, 24°C, and 30°C, respectively. Gene expression profiles for 'Ca. L. solanacearum'-infected and -uninfected adult psyllids reared at different temperatures were characterized by Illumina RNA-Seq analysis. Bacterial genome copy number was quantified by real-time quantitative-PCR (qPCR) amplification.

Results

Relative gene expression profiles varied in psyllids reared at the three experimental temperatures. Psyllids reared at 18°C and 30°C exhibited greater fold-change increased expression of stress- and 'Ca. L. solanacearum' invasion-related proteins. Quantification by qPCR of bacterial genome copy number revealed that 'Ca. L. solanacearum' accumulation was significantly lower in psyllids reared at 18°C and 30°C, compared to 24°C.

Discussion

Temperature is a key factor in the life history of potato psyllid and multiplication/accumulation of 'Ca. L. solanacearum' in both the plant and psyllid host, influences the expression of genes associated with thermal stress tolerance, among others, and may have been instrumental in driving the co-evolution of the pathosystem.

Climatic gradients and forest composition shape bat communities in Eastern Mediterranean pine plantations

Biotic and abiotic factors can act as filters for determining the species composition of biological communities. We aimed to identify abiotic factors driving the assembly of bat communities in Eastern Mediterranean pine plantations along a north-south climatic gradient, as they are crucial forest habitats for the assessment and conservation of these communities. We expected that bat communities are predominantly shaped by environmental filtering. We conducted acoustic sampling in 35 pine plantations in Israel and analyzed recordings for species identification. We used the ESLTP analysis, an extension of the three-table ordination (RLQ analysis), to explore relationships between environmental characteristics, species occurrences, and functional traits of species while accounting for phylogenetic relationships between species and spatial distribution of the communities. Communities showed phylogenetic and trait clustering. Climatic conditions and forest vegetation composition shaped communities of bats, affecting the distribution of traits related to foraging behaviors, vegetation clutter, and the ability of bats to maneuver in it. Maneuverable species were associated with the northern Mediterranean climatic zone, with a scarce cover of drought-tolerant small shrubs and grassland. Fast flyers were associated with the center-south semi-arid area, with abundant drought-tolerant small shrubs and grassland. These forces might have a predominant role in the assembly of these communities, presumably due to the stressful climatic conditions of the study area. The ESLTP approach can be extended to other taxa and environments to predict species responses to disturbance and environmental changes and give insights into environmental management.

1-nonene plays an important role in the response of maize-aphid-ladybird tritrophic interactions to nitrogen

Plant volatile organic compounds (VOCs) are the key distress signals involved in tritrophic interactions, by which plants recruit predators to protect themselves from herbivores. However, the effect of nitrogen fertilization on VOCs that mediate tritrophic interactions remains largely unidentified. In this study, a maize (Zea mays)-aphid (Rhopalosiphum padi)-ladybird (Harmonia axyridis) tritrophic interaction model was constructed under high-nitrogen (HN) and low-nitrogen (LN) regimens. H. axyridis had a stronger tendency to be attracted by aphid-infested maize under HN conditions. Then, volatiles were collected and identified from maize leaves on which aphids had fed. All of the HN-induced volatiles (HNIVs) elicited an electroantennogram (EAG) response from H. axyridis. Of these HNIVs, 1-nonene was attractive to H. axyridis under simulated natural volatilization. Furthermore, our regression showed that the release of 1-nonene was positively correlated with H. axyridis visitation rates. Supplying 1-nonene to maize on which aphids had fed under LN enhanced attractiveness to H. axyridis. These results supported the conclusion that 1-nonene was the active compound that mediated the response to nitrogen in the tritrophic interaction. In addition, the 1-nonene synthesis pathway was hypothesized, and we found that the release of 1-nonene might be related to the presence of salicylic acid (SA) and abscisic acid (ABA). This research contributes to the development of novel environmentally friendly strategies to optimize nitrogen fertilizer application and to improve pest control in maize crops.

Phenological Mapping of Invasive Insects: Decision Support for Surveillance and Management

Readily accessible and easily understood forecasts of the phenology of invasive insects have the potential to support and improve strategic and tactical decisions for insect surveillance and management. However, most phenological modeling tools developed to date are site-based, meaning that they use data from a weather station to produce forecasts for that single site. Spatial forecasts of phenology, or phenological maps, are more useful for decision-making at area-wide scales, such as counties, states, or entire nations. In this review, we provide a brief history on the development of phenological mapping technologies with a focus on degree-day models and their use as decision support tools for invasive insect species. We compare three different types of phenological maps and provide examples using outputs of web-based platforms that are presently available for real-time mapping of invasive insects for the contiguous United States. Next, we summarize sources of climate data available for real-time mapping, applications of phenological maps, strategies for balancing model complexity and simplicity, data sources and methods for validating spatial phenology models, and potential sources of model error and uncertainty. Lastly, we make suggestions for future research that may improve the quality and utility of phenological maps for invasive insects.

Humidity - The overlooked variable in the thermal biology of mosquito-borne disease

Vector-borne diseases cause significant financial and human loss, with billions of dollars spent on control. Arthropod vectors experience a complex suite of environmental factors that affect fitness, population growth and species interactions across multiple spatial and temporal scales. Temperature and water availability are two of the most important abiotic variables influencing their distributions and abundances. While extensive research on temperature exists, the influence of humidity on vector and pathogen parameters affecting disease dynamics are less understood. Humidity is often underemphasized, and when considered, is often treated as independent of temperature even though desiccation likely contributes to declines in trait performance at warmer temperatures. This Perspectives explores how humidity shapes the thermal performance of mosquito-borne pathogen transmission. We summarize what is known about its effects and propose a conceptual model for how temperature and humidity interact to shape the range of temperatures across which mosquitoes persist and achieve high transmission potential. We discuss how failing to account for these interactions hinders efforts to forecast transmission dynamics and respond to epidemics of mosquito-borne infections. We outline future research areas that will ground the effects of humidity on the thermal biology of pathogen transmission in a theoretical and empirical framework to improve spatial and temporal prediction of vector-borne pathogen transmission.

Effects of air humidity and soil moisture on secondary metabolites in the leaves and roots of Betula pendula of different competitive status

Plant secondary metabolites (PSMs) defend plants against abiotic stresses, including those caused by climate change and against biotic stresses, such as herbivory and competition. There is a trade-off between allocating available carbon to growth and defence in stressful environments. However, our knowledge about trade-off is limited, especially when abiotic and biotic stresses co-occur. We aimed to understand the combined effect of increasing precipitation and humidity, the tree's competitive status, and canopy position on leaf secondary metabolites (LSMs) and fine root secondary metabolites (RSMs) in Betula pendula. We sampled 8-year-old B. pendula trees growing in the free air humidity manipulation (FAHM) experimental site, where treatments included elevated relative air humidity and elevated soil moisture. A high-performance liquid chromatography-quadrupole-time of flight mass spectrometer (HPLC-qTOF-MS) was used to analyse secondary metabolites. Our results showed accumulation of LSM depends on the canopy position and competitive status. Flavonoids (FLA), dihydroxybenzoic acids (HBA), jasmonates (JA) and terpene glucosides (TG) were higher in the upper canopy, and FLA, monoaryl compounds (MAR) and sesquiterpenoids (ST) were higher in dominant trees. The FAHM treatments had a more distinct effect on RSM than on LSM. The RSMs were lower in elevated air humidity and soil moisture conditions than in control conditions. The RSM content depended on the competitive status and was higher in suppressed trees. Our study suggests that young B. pendula will allocate similar amounts of carbon to constitutive chemical leaf defence, but a lower amount to root defence (per fine root biomass) under higher humidity.

Water availability and plant-herbivore interactions

Water is essential to plant growth and drives plant evolution and interactions with other organisms such as herbivores. However, water availability fluctuates, and these fluctuations are intensified by climate change. How plant water availability influences plant-herbivore interactions in the future is an important question in basic and applied ecology. Here we summarize and synthesize the recent discoveries on the impact of water availability on plant antiherbivore defense ecology and the underlying physiological processes. Water deficit tends to enhance plant resistance and escape traits (i.e. early phenology) against herbivory but negatively affects other defense strategies, including indirect defense and tolerance. However, exceptions are sometimes observed in specific plant-herbivore species pairs. We discuss the effect of water availability on species interactions associated with plants and herbivores from individual to community levels and how these interactions drive plant evolution. Although water stress and many other abiotic stresses are predicted to increase in intensity and frequency due to climate change, we identify a significant lack of study on the interactive impact of additional abiotic stressors on water-plant-herbivore interactions. This review summarizes critical knowledge gaps and informs possible future research directions in water-plant-herbivore interactions.

Assemblage of Ceutorhynchinae Weevils Associated With Brassicaceae in Quebec (Canada) Agroecosystems

Ceutorhynchinae Gistel (Coleoptera: Curculionidae) are a highly diverse phytophagous group of weevils in which the most species rich genus, Ceutorhynchus Germar (Coleoptera: Curculionidae), is mainly associated with Brassicaceae. Some Ceutorhynchinae, such as the invasive cabbage seedpod weevil (CSW), Ceutorhynchus obstrictus (Marsham), are important pests of cultivated Brassicaceae, and others are natural enemies of weeds and potential biological control agents. This study aims to characterize Ceutorhynchinae assemblages in canola growing regions of Quebec. Ceutorhynchinae were sampled in areas adjacent to canola fields or other crops in six administrative regions of Quebec during the summers of 2019 and 2020. A total of 25 Ceutorhynchinae species were collected and identified. Canonical analysis and multivariate regression tree analysis revealed that the assemblage of Ceutorhynchinae varied regionally and was either dominated by the invasive canola pest CSW or by the native weevil Ceutorhynchus neglectus Blatchley. Our results also highlighted new biological associations between weevils and Brassicaceae like the CSW with the yellow rocket, Barbarea vulgaris R. Br., native Ceutorhynchus pauxillus Dietz with common pepper grass, Lepidium densiflorum, and native Ceutorhynchus semirufus LeConte with Pennsylvania bittercress, Cardamine pensylvanica Muhl. This study also provides a useful tool to find new biological control agents against Brassicaceae weeds and to monitor the abundance and diversity of this taxon and provide baseline data to assess future impacts of exotic parasitoids of CSW on native weevils.

The timing of heat waves has multiyear effects on milkweed and its insect community

Extreme heat events are becoming more frequent and intense as climate variability increases, and these events inherently vary in their timing. We predicted that the timing of a heat wave would determine its consequences for insect communities owing to temporal variation in the susceptibility of host plants to heat stress. We subjected common milkweed (Asclepias syriaca) plants to in-field experimental heat waves to investigate how the timing of heat waves, both seasonally and relative to a biotic stressor (experimental herbivory), affected their ecological consequences. We found that heat waves had multiyear, timing-specific effects on plant-insect communities. Early-season heat waves led to greater and more persistent effects on plants and herbivore communities than late-season heat waves. Heat waves following experimental herbivory had reduced consequences. Our results show that extreme climate events can have complex, lasting ecological effects beyond the year of the event-and that timing is key to understanding those effects.

Alternative developmental and transcriptomic responses to host plant water limitation in a butterfly metapopulation

Predicting how climate change affects biotic interactions poses a challenge. Plant-insect herbivore interactions are particularly sensitive to climate change, as climate-induced changes in plant quality cascade into the performance of insect herbivores. Whereas the immediate survival of herbivore individuals depends on plastic responses to climate change-induced nutritional stress, long-term population persistence via evolutionary adaptation requires genetic variation for these responses. To assess the prospects for population persistence under climate change, it is therefore crucial to characterize response mechanisms to climate change-induced stressors, and quantify their variability in natural populations. Here, we test developmental and transcriptomic responses to water limitation-induced host plant quality change in a Glanville fritillary butterfly (Melitaea cinxia) metapopulation. We combine nuclear magnetic resonance spectroscopy on the plant metabolome, larval developmental assays and an RNA sequencing analysis of the larval transcriptome. We observed that responses to feeding on water-limited plants, in which amino acids and aromatic compounds are enriched, showed marked variation within the metapopulation, with individuals of some families performing better on control and others on water-limited plants. The transcriptomic responses were concordant with the developmental responses: families exhibiting opposite developmental responses also produced opposite transcriptomic responses (e.g. in growth-associated transcripts). The divergent responses in both larval development and transcriptome are associated with differences between families in amino acid catabolism and storage protein production. The results reveal intrapopulation variability in plasticity, suggesting that the Finnish M. cinxia metapopulation harbours potential for buffering against drought-induced changes in host plant quality.

Yearly weather variation and surface temperature drives the spatiotemporal dynamics of a threatened butterfly and its host plant

It remains unclear to what extent yearly weather variation and spatial variation in microclimate influences the outcome of interacting plant-animal species and whether responses differ between life stages. We collected data over several years on 46 ha on File Hajdar, Gotland, Sweden, and executed a complete mapping of larva nests (n = 776) and imago (n = 5,952) of the marsh fritillary butterfly Euphydryas aurinia and its host plant Succisa pratensis. The phenology of the butterflies and the major nectar plants visited varied among years. The duration of the adult flight period decreased with increasing ambient air temperatures. The density of butterflies, host plants, and host plant leaf size increased between years with increasing precipitation in the preceding year, and decreased with increasing average ambient air temperature in the preceding year. In 2021–2022 we deployed a unmanned aerial vehicle (UAV) with a high-resolution thermal sensor to measure spatial variation in surface temperatures in the study area. We found that survival from the egg to the larva stage increased with increasing surface temperature and host plant density. Host plants and larva nests generally occupied warmer microhabitats compared to imago butterflies. The results further suggested that the relationships linking surface temperature to the densities of imago, larva, host plants, and leaf size differed qualitatively between years. In 2017, larva nests and host plant density increased with increasing surface temperatures, and butterflies showed a non-linear response with a density peak at intermediate temperatures. As a result of the extreme drought in 2018 there was a reduction in maximum leaf size, and in the densities of plants, larvae, and butterflies. Moreover, the slopes of the relationships linking the density of larvae, butterflies, and plants to temperature shifted from linear positive to negative or curvilinear. Our findings demonstrate how yearly weather variation and heterogeneous surface temperatures can drive the spatiotemporal distribution and dynamics of butterflies and their host plants. The context specificity of the responses indicated by our results makes it challenging to project how climate change will affect the dynamics of ecological communities.

Ontogeny-dependent effects of elevated CO2 and watering frequency on interaction between Aristolochia contorta and its herbivores

Effects of environmental change on plants can differ due to sequential changes in their life-history strategies (i.e., ontogenetic variations). The fitness of herbivorous insects by physiological changes of the host plant could be affected depending on their diet breadth. However, little is known regarding the combinational effects of plant ontogeny and climate change on plant-herbivore interactions. This study examined the plant ontogeny-dependent effects of climate change on the interaction between a host plant (Aristolochia contorta), its specialist herbivore (Sericinus montela), and a generalist herbivore (Spodoptera exigua). Plants were grown under a factorial design of two distinct CO₂ concentrations (ambient, 400 ppm; elevated, 560 ppm) and two watering frequencies (control, once a week; increased, twice a week). Plant ontogeny ameliorated the effects of climate change by altering its defensive traits, where nutrient-related factors were cumulatively affected by climate change. Herbivore performance was assessed at three different plant ontogenetic stages (1st-year juvenile, 1st-year senescence, and 2nd-year juvenile). Elevated CO₂ levels reduced the growth and survival of the specialist herbivore, whereas increased watering frequency partially alleviated this reduced performance. Generalist herbivore performance slightly increased under elevated CO₂ levels with progressing ontogenetic stages. The effects of climate change, both elevated CO₂ and increased watering frequency were weaker in 2nd-year juveniles than in 1st-year juveniles. Elevated CO₂ levels detrimentally affected the nutritional quality of A. contorta leaves. The effects of climate change on both specialist and generalist herbivore performance differed as plant ontogenetic stage proceeded. Increased growth rates and survival of the generalist herbivore at the latter ontogenetic stage might negatively affect the population dynamics of a specialist herbivore. This study suggests that biases are possible when the plant-herbivore interaction under a changing environment is predicted from a singular plant ontogenetic stage.

Opposing global change drivers counterbalance trends in breeding North American monarch butterflies

Many insects are in clear decline, with monarch butterflies (Danaus plexippus) drawing particular attention as a flagship species. It is well documented that, among migratory populations, numbers of overwintering monarchs have been falling across several decades, but trends among breeding monarchs are less clear. Here, we compile >135,000 monarch observations between 1993 and 2018 from the North American Butterfly Association's annual butterfly count to examine spatiotemporal patterns and potential drivers of adult monarch relative abundance trends across the entire breeding range in eastern and western North America. While the data revealed declines at some sites, particularly the US Northeast and parts of the Midwest, numbers in other areas, notably the US Southeast and Northwest, were unchanged or increasing, yielding a slightly positive overall trend across the species range. Negative impacts of agricultural glyphosate use appeared to be counterbalanced by positive effects of annual temperature, particularly in the US Midwest. Overall, our results suggest that population growth in summer is compensating for losses during the winter and that changing environmental variables have offsetting effects on mortality and/or reproduction. We suggest that density-dependent reproductive compensation when lower numbers arrive each spring is currently able to maintain relatively stable breeding monarch numbers. However, we caution against complacency since accelerating climate change may bring growing threats. In addition, increases of summer monarchs in some regions, especially in California and in the south, may reflect replacement of migratory with resident populations. Nonetheless, it is perhaps reassuring that ubiquitous downward trends in summer monarch abundance are not evident.

Multidecadal, continent-level analysis indicates agricultural practices impact wheat aphid loads more than climate change

Temperature has a large influence on insect abundances, thus under climate change, identifying major drivers affecting pest insect populations is critical to world food security and agricultural ecosystem health. Here, we conducted a meta-analysis with data obtained from 120 studies across China and Europe from 1970 to 2017 to reveal how climate and agricultural practices affect populations of wheat aphids. Here we showed that aphid loads on wheat had distinct patterns between these two regions, with a significant increase in China but a decrease in Europe over this time period. Although temperature increased over this period in both regions, we found no evidence showing climate warming affected aphid loads. Rather, differences in pesticide use, fertilization, land use, and natural enemies between China and Europe may be key factors accounting for differences in aphid pest populations. These long-term data suggest that agricultural practices impact wheat aphid loads more than climate warming.

Impact of climate change on the elevational and latitudinal distributions of populations of Tipulidae (Diptera) in Wales, United Kingdom

As dominant features of most ecosystems, insects are responsive to changes in climate, both over short temporal scales (e.g. seasonal fluctuations in abundance) and over longer evolutionary scales (e.g. decade-scale changes in patterns of biodiversity). One such taxonomic group that is sensitive to changing climate are the craneflies (Diptera: Tipulidae). Here, we used aggregated biodiversity data to examine elevational and latitudinal distributions of adult Tipulidae between 1976 and 2019 in Wales, UK, and we related these distributions to climatic patterns. Our analyses showed that species with earlier-emerging adults were most affected by weather conditions in the year before observation. Specifically, as temperature increased, observed elevation increased in high-precipitation conditions, remained stable in average-precipitation conditions and decreased in low-precipitation conditions. For species with later-emerging adults, associations were seen between elevation and weather conditions in the year of observation. Observed latitude generally exhibited a negative association with maximum temperature in the year before observation, with observations of Tipulidae trending southwards during the 43-year study period. Our results support consideration of emergence phenology, weather and habitat data when predicting species distributional changes attributable to climate change, which is vital in understanding the selection pressures that species face in a changing environment.

Precipitation change accentuates or reverses temperature effects on aphid dispersal

Global temperatures are generally increasing, and this is leading to a well documented advancement and extension of seasonal activity of many pest insects. Effects of changing precipitation have received less attention, but might be complex because rain and snow are increasing in some places but decreasing in others. This raises the possibility that altered precipitation could accentuate, or even reverse, the effects of rising temperatures on pest outbreaks. We used >592 K aphid suction-trap captures over 15 years, in the heavily farmed central USA, to examine how the activity of Aphis glycines (soybean aphid), Rhopalosiphum maidis (corn aphid), and Rhopalosiphum padi (bird cherry-oat aphid) changed with variation in both temperature and precipitation. Increasing precipitation caused late-season flight activity of A. glycines and early-season activity of R. padi to shift earlier, while increasing temperature did the same for early-season activity of A. glycines and R. maidis. In these cases, precipitation and temperature exhibited directionally similar, but independent, effects. However, precipitation sometimes mediated temperature effects in complex ways. At relatively low temperatures, greater precipitation generally caused late-season flights of R. maidis to occur earlier. However, this pattern was reversed at higher temperatures with precipitation delaying late-season activity. In contrast, greater precipitation delayed peak flights of R. padi at lower temperatures, but caused them to occur earlier at higher temperatures. So, in these two cases the interactive effects of precipitation on temperature were mirror images of one another. When projecting future aphid flight phenology, models that excluded precipitation covariates consistently underpredicted the degree of phenological advance for A. glycines and R. padi, and underpredicted the degree of phenological delay for R. maidis under expected future climates. Overall, we found broad evidence that changing patterns of aphid flight phenology could only be understood by considering both temperature and precipitation changes. In our study region, temperature and precipitation are expected to increase in tandem, but these correlations will be reversed elsewhere. This reinforces the need to include both main and interactive effects of precipitation and temperature when seeking to accurately predict how pest pressure will change with a changing climate.

Herbivory on the pedunculate oak along an urbanization gradient in Europe: Effects of impervious surface, local tree cover, and insect feeding guild

Urbanization is an important driver of the diversity and abundance of tree-associated insect herbivores, but its consequences for insect herbivory are poorly understood. A likely source of variability among studies is the insufficient consideration of intra-urban variability in forest cover. With the help of citizen scientists, we investigated the independent and interactive effects of local canopy cover and percentage of impervious surface on insect herbivory in the pedunculate oak (Quercus robur L.) throughout most of its geographic range in Europe. We found that the damage caused by chewing insect herbivores as well as the incidence of leaf-mining and gall-inducing herbivores consistently decreased with increasing impervious surface around focal oaks. Herbivory by chewing herbivores increased with increasing forest cover, regardless of impervious surface. In contrast, an increase in local canopy cover buffered the negative effect of impervious surface on leaf miners and strengthened its effect on gall inducers. These results show that-just like in non-urban areas-plant-herbivore interactions in cities are structured by a complex set of interacting factors. This highlights that local habitat characteristics within cities have the potential to attenuate or modify the effect of impervious surfaces on biotic interactions.

The Ant-like Tachydromia Complex in the Iberian Peninsula-Insights from Habitat Suitability Modelling for the Conservation of an Endemism (Diptera: Hybotidae)

Simple Summary

The ant-like flies are a group of nine species of flightless Tachydromia, with their distribution restricted to the Iberian Peninsula. Severe knowledge gaps regarding their distribution and ecological requirements hinder conservation assessments. To improve this scenario, an ensemble of 9 different species distribution models was applied to unveil habitat suitability and to provide guidelines for future studies. The most important factors influencing habitat suitability are climate-related, followed by forest type and structure, with well-defined biogeographic gradients. T. lusitanica and T. ebejeri are adapted to the mild temperature and high-humidity environments, typical of the Temperate–Eurosiberian life zone. T. semiaptera and T. iberica are adapted to progressively drier and hotter central and southern parts of the Iberian Peninsula, connected to transitional Temperate–submediterranean areas. Ant-like flies’ distribution overlaps with deciduous/ marcescent oak species, which can effectively indicate their presence in Iberia. Additionally, southern marcescent forests emerge as “islands” with particular interest for future fieldwork. Ant-like flies are threatened by several factors such as climate change and habitat destruction, including urbanization and forest fires. This study provides vital tools to better assess the ant-like flies’ conservation status and to manage their habitat.

Abstract

Ant-like flies comprise nine Iberian endemic species of flightless Tachydromia. Severe knowledge gaps on distribution and ecological requirements hinder conservation assessments. Species distribution models were applied to unveil habitat suitability and to provide guidelines for future studies. An ensemble modeling approach combining ten different techniques was implemented with the biomod2 package. Occurrence data was partitioned into six sets, including two multi-species groups and four species. The most relevant drivers of habitat suitability are climate-related, followed by forest type and structure, according to well-defined biogeographic gradients. T. lusitanica and T. ebejeri are adapted to mild temperatures and high-humidity environments. Their distribution is connected to the Temperate–Eurosiberian life zone. T. semiaptera and T. iberica are adapted to progressively drier and hotter central and southern parts of the Iberian Peninsula, connected to transitional Temperate–submediterranean areas. Ant-like fly’ ranges overlap with deciduous/marcescent oak species, acting as suitable indicators of their presence in Iberia. Southern marcescent forests emerge as “islands” with particular interest for future prospections. Ant-like flies are threatened by several factors such as climate change and habitat destruction, including urbanization and forest fires. This study provides vital tools to better assess the ant-like flies’ conservation status and to manage their habitat.

Climate change effects on animal ecology: butterflies and moths as a case study

Butterflies and moths (Lepidoptera) are one of the most studied, diverse, and widespread animal groups, making them an ideal model for climate change research. They are a particularly informative model for studying the effects of climate change on species ecology because they are ectotherms that thermoregulate with a suite of physiological, behavioural, and phenotypic traits. While some species have been negatively impacted by climatic disturbances, others have prospered, largely in accordance with their diversity in life-history traits. Here we take advantage of a large repertoire of studies on butterflies and moths to provide a review of the many ways in which climate change is impacting insects, animals, and ecosystems. By studying these climate-based impacts on ecological processes of Lepidoptera, we propose appropriate strategies for species conservation and habitat management broadly across animals.

Cracking the code: a comparative approach to plant communication

The linguistic behavior of humans is usually considered the point of reference for studying the origin and evolution of language. As commonly defined, language is a form of communication between human beings; many have argued that it is unique to humans as there is no apparent equivalent for it in non-human organisms. How language is used as a means of communication is examined in this essay from a biological perspective positing that it is effectively and meaningfully used by non-human organisms and, more specifically, by plants. We set out to draw parallels between some aspects characterizing human language and the chemical communication that occurs between plants. The essay examines the similarities in ways of communicating linked to three properties of language: its combinatorial structure, meaning-making activities and the existence of dialects. In accordance with the findings of researchers who have demonstrated that plants do indeed communicate with one another and with organisms in their environment, the essay concludes with the appeal for an interdisciplinary approach conceptualizing a broader ecological definition of language and a constructive dialogue between the biological sciences and the humanities.

Climate Change Modulates Multitrophic Interactions Between Maize, A Root Herbivore, and Its Enemies

How climate change will modify belowground tritrophic interactions is poorly understood, despite their importance for agricultural productivity. Here, we manipulated the three major abiotic factors associated with climate change (atmospheric CO₂, temperature, and soil moisture) and investigated their individual and joint effects on the interaction between maize, the banded cucumber beetle (Diabrotica balteata), and the entomopathogenic nematode (EPN) Heterorhabditis bacteriophora. Changes in individual abiotic parameters had a strong influence on plant biomass, leaf wilting, sugar concentrations, protein levels, and benzoxazinoid contents. Yet, when combined to simulate a predicted climate scenario (Representative Concentration Pathway 8.5, RCP 8.5), their effects mostly counter-balanced each other. Only the sharp negative impact of drought on leaf wilting was not fully compensated. In both current and predicted scenarios, root damage resulted in increased leaf wilting, reduced root biomass, and reconfigured the plant sugar metabolism. Single climatic variables modulated the herbivore performance and survival in an additive manner, although slight interactions were also observed. Increased temperature and CO₂ levels both enhanced the performance of the insect, but elevated temperature also decreased its survival. Elevated temperatures and CO₂ further directly impeded the EPN infectivity potential, while lower moisture levels improved it through plant- and/or herbivore-mediated changes. In the RCP 8.5 scenario, temperature and CO₂ showed interactive effects on EPN infectivity, which was overall decreased by 40%. We conclude that root pest problems may worsen with climate change due to increased herbivore performance and reduced top-down control by biological control agents.

Climatic displacement exacerbates the negative impact of drought on plant performance and associated arthropod abundance

Climate change is acting on species and modifying communities and ecosystems through changes not only with respect to mean abiotic conditions, but also through increases in the frequency and severity of extreme events. Changes in mean aridity associated with climate change can generate ecotype by environment mismatch (i.e., climatic displacement). At the same time, variability around these shifting means is predicted to increase, resulting in more extreme droughts. We characterized the effects of two axes of climate change, climatic displacement and drought, on the shrub Artemisia californica and its arthropods. We established common gardens of plants sourced along an aridity gradient (3.5-fold variation in mean annual precipitation) in an arid region of the species distribution, thus generating a gradient of climatic displacement (sustained increase in aridity) as predicted with climate change. We surveyed plants and arthropods over eight years where precipitation varied sixfold, including both extreme drought and relatively mesic conditions. These two axes of climate change interacted to influence plant performance, such that climatically displaced populations grew slowly regardless of drought and suffered substantial mortality during drought years. Conversely, local populations grew quickly, increased growth during wet years, and had low mortality regardless of drought. Effects on plant annual arthropod yield were negative and additive, with drought effects exceeding that of climatic displacement by 24%. However, for plant lifetime arthropod yield, incorporating effects on both plant growth and survival, climatic displacement exacerbated the negative effects of drought. Collectively these results demonstrate how climatic displacement (through increasing aridity stress) strengthens the negative effects of drought on plants and, indirectly, on arthropods, suggesting the possibility of climate-mediated trophic collapse.

Characterisation of Vegetation Response to Climate Change: A Review

Climate change extreme events have consequential impacts that influence the responses of vegetation dynamics as well as ecosystem functioning and sustainable human well-being. Therefore, vegetation response to climate change (VRCC) needs to be explored to foster specific-organised management programmes towards ecological conservation and targeted restoration policy to various climate extreme threats. This review aimed to explore the existing literature to characterise VRCC and to identify solutions and techniques fundamental in designing strategies for targeted effective adaptation and mitigation to achieve sustainable planning outcomes. Accordingly, this review emphasised recent theoretical and practical research on the vegetation-climate responses and their related impacts in the wake of climate change and its debilitating impacts on vegetation. Consequently, this study proposes the Information-based model (IBM), needed to examine Factors–forms of Impacts–Solutions (Techniques)–Risks assessment to identify and provide insights about VRCC in a given region. In conclusion, two enablers of adaptive indicators and the novel systems-based serve as a key policy formulation for sustainability in strengthening the goals of global involvement of local and sub-national governments and institutions in the effective management of vegetation and ecosystem protection.

Impact of Temperature on Survival Rate, Fecundity, and Feeding Behavior of Two Aphids, Aphis gossypii and Acyrthosiphon gossypii, When Reared on Cotton

Aphid performance is sensitive to temperature changes. Previous studies found that Acyrthosiphon gossypii (Mordviiko) was more sensitive to high temperature than Aphis gossypii (Glover). However, the effects of high temperatures on the survival, fecundity, and feeding behavior of these two aphid adults are not clear. This study examined the effect of different temperatures (29 °C, 32 °C, and 35 °C) on the adult survival rate, fecundity, and feeding behavior of these two aphid species. Our results showed that the adverse effects of high temperatures (32 °C and 35 °C) on aphid adult survival and fecundity were greater for Ac. gossypii than Ap. gossypii. The electrical penetration graph (EPG) data showed that Ac. gossypii spent more time feeding on xylem than phloem under all temperature treatments, which contrasted with Ap. gossypii. The time of phloem ingestion by Ap. gossypii at 32 °C was significantly higher than at 29 °C, while for Ac. gossypii, this value significantly decreased when temperature increased. These feeding patterns indicate that Ac. gossypii obtains less nutrition from phloem in support of its development and fecundity. Data generated in this study will serve as the basis for predicting the effects of increased temperature on these two cotton aphids.

The Impact of Climate Change on Agricultural Insect Pests

Climate change and global warming are of great concern to agriculture worldwide and are among the most discussed issues in today's society. Climate parameters such as increased temperatures, rising atmospheric CO2 levels, and changing precipitation patterns have significant impacts on agricultural production and on agricultural insect pests. Changes in climate can affect insect pests in several ways. They can result in an expansion of their geographic distribution, increased survival during overwintering, increased number of generations, altered synchrony between plants and pests, altered interspecific interaction, increased risk of invasion by migratory pests, increased incidence of insect-transmitted plant diseases, and reduced effectiveness of biological control, especially natural enemies. As a result, there is a serious risk of crop economic losses, as well as a challenge to human food security. As a major driver of pest population dynamics, climate change will require adaptive management strategies to deal with the changing status of pests. Several priorities can be identified for future research on the effects of climatic changes on agricultural insect pests. These include modified integrated pest management tactics, monitoring climate and pest populations, and the use of modelling prediction tools.

Trophic match/mismatch and reproduction of the pied flycatcher Ficedula hypoleuca in a metal-polluted area

In polluted areas, birds can suffer from changes in diet composition and inferior food quality. It is unknown if pollution can desynchronize the phenology of birds and their prey, resulting in a mismatch between food demand and availability. For 2 years, we studied seasonal changes in the biomass of leaf-eating invertebrates and the timing of reproduction and breeding success of an insectivorous bird, the pied flycatcher, in an area heavily polluted by the Middle Ural copper smelter and in an unpolluted control area. Seasonal variations in herbivore biomass were relatively synchronous in polluted and unpolluted areas, whereas birds started breeding later in the polluted area. In the year with an earlier spring, the herbivore peak was early and short, resulting in lower food availability for birds feeding nestlings. The greater the mismatch between food demand and availability the higher was the frequency of nests containing perished nestlings and the lower the body mass of fledglings. Our data did not support the hypothesis that the detrimental effect of the trophic mismatch on birds is greater in the polluted area than in the unpolluted one. Nevertheless, delayed breeding in the pied flycatcher in polluted areas suggests a higher probability of mistimed bird reproduction in the years with a short period of food abundance. Thus, the synchrony of phenology of birds and their prey is an important pollution-related factor that should be taken into account when analyzing the effects of pollution on birds.

Natural enemies of herbivores maintain their biological control potential under short-term exposure to future CO2, temperature, and precipitation patterns

Climate change will profoundly alter the physiology and ecology of plants, insect herbivores, and their natural enemies, resulting in strong effects on multitrophic interactions. Yet, manipulative studies that investigate the direct combined impacts of changes in CO2, temperature, and precipitation on the third trophic level remain rare. Here, we assessed how exposure to elevated CO2, increased temperature, and decreased precipitation directly affect the performance and predation success of species from four major groups of herbivore natural enemies: an entomopathogenic nematode, a wolf spider, a ladybug, and a parasitoid wasp. A four-day exposure to future climatic conditions (RCP 8.5), entailing a 28% decrease in precipitation, a 3.4°C raise in temperature, and a 400 ppm increase in CO2 levels, slightly reduced the survival of entomopathogenic nematodes, but had no effect on the survival of other species. Predation success was not negatively affected in any of the tested species, but it was even increased for wolf spiders and entomopathogenic nematodes. Factorial manipulation of climate variables revealed a positive effect of reduced soil moisture on nematode infectivity, but not of increased temperature or elevated CO2. These results suggest that natural enemies of herbivores may be well adapted to short-term changes in climatic conditions. These findings provide mechanistic insights that will inform future efforts to disentangle the complex interplay of biotic and abiotic factors that drive climate-dependent changes in multitrophic interaction networks.

Impact of Phytophthora agathidicida infection on canopy and forest floor plant nutrient concentrations and fluxes in a kauri-dominated forest

Kauri dieback, caused by Phytophthora agathidicida, is a biotic disturbance that poses a recent threat to the survival of kauri (Agathis australis) forests in New Zealand. Previous studies have shown that throughfall and stemflow play an important role in the kauri forests' internal nutrient cycle. However, the effects of P. agathidicida infection on canopy and forest floor nutrient fluxes in kauri forests remain unknown. Here, we measured throughfall, stemflow and forest floor water yield, nutrient (potassium, calcium, magnesium, manganese, silicon, sulfur, sodium, iron) concentrations and fluxes of ten kauri trees differing in soil P. agathidicida DNA concentration, and health status. We did not observe an effect of soil P. agathidicida DNA concentration on throughfall, stemflow, and forest floor water yield. Throughfall and forest floor nutrient concentrations and fluxes decreased (up to 50%) with increasing soil P. agathidicida DNA concentration. We found significant effects on potassium and manganese fluxes in throughfall; calcium and silicon fluxes in forest floor leachate. A decline in canopy and forest floor nutrient fluxes may result in soil nutrient imbalances, which in turn may negatively impact forest productivity and may increase the susceptibility of trees to future pathogen infection in these ecologically unique kauri forests. Given our findings and the increasing spread of Phytophthora species worldwide, research on the underlying physiological mechanisms linking dieback and plant-soil nutrient fluxes is critical.

Assessment and Models of Insect Damage to Cones and Seeds of Pinus strobiformis in the Sierra Madre Occidental, Mexico

Insect damage to cones and seeds has a strong impact on the regeneration of conifer forest ecosystems, with broader implications for ecological and economic services. Lack of control of insect populations can lead to important economic and environmental losses. Pinus strobiformis is the most widespread of the white pines in Mexico and is widely distributed throughout the mountains of northern Mexico. Relatively few studies have examined insect damage to the cones and seeds of these pines, especially in Mexico. In this study, we therefore analyzed insect damage to cones and seeds of P. strobiformis in Mexico by using X-ray and stereomicroscopic analysis. The specific objectives of the study were (a) to characterize insect damage by measuring external and internal cone traits, (b) to assess the health of seeds and cones of P. strobiformis in the Sierra Madre Occidental, Mexico, and (c) to estimate the relative importance of the effects of different environmental variables on cone and seed damage caused by insects. We found that 80% of P. strobiformis seeds and 100% of the tree populations studied had damage caused by insects. Most seeds were affected by Leptoglossus occidentalis, Tetyra bipunctata, Megastigmus albifrons, and the Lepidoptera complex (which includes Apolychrosis synchysis, Cydia latisigna, Eucosma bobana, and Dioryctria abietivorella). The cones of all tree populations were affected by some type of insect damage, with Lepidoptera causing most of the damage (72%), followed by Conophthorus ponderosae (15%), the hemipteran L. occidentalis (7%), and the wasp M. albifrons (6%). The proportion of incomplete seeds in P. strobiformis at the tree level, cone damage by M. albifrons and seed damage in L. occidentalis were associated with various climate and soil variables and with crown dieback. Thus, cone and seed insect damage can be severe and potentially impact seed production in P. strobiformis and the reforestation potential of the species. The study findings will enable managers to better identify insects that cause damage to cone and seeds. In addition, identification of factors associated with damage may be useful for predicting the levels of insect predation on seeds and cones.

Experimental Test of the Combined Effects of Water Availability and Flowering Time on Pollinator Visitation and Seed Set

Climate change is likely to alter both flowering phenology and water availability for plants. Either of these changes alone can affect pollinator visitation and plant reproductive success. The relative impacts of phenology and water, and whether they interact in their impacts on plant reproductive success remain, however, largely unexplored. We manipulated flowering phenology and soil moisture in a factorial experiment with the subalpine perennial Mertensia ciliata (Boraginaceae). We examined responses of floral traits, floral abundance, pollinator visitation, and composition of visits by bumblebees vs. other pollinators. To determine the net effects on plant reproductive success, we also measured seed production and seed mass. Reduced water led to shorter, narrower flowers that produced less nectar. Late flowering plants produced fewer and shorter flowers. Both flowering phenology and water availability influenced pollination and reproductive success. Differences in flowering phenology had greater effects on pollinator visitation than did changes in water availability, but the reverse was true for seed production and mass, which were enhanced by greater water availability. The probability of receiving a flower visit declined over the season, coinciding with a decline in floral abundance in the arrays. Among plants receiving visits, both the visitation rate and percent of non-bumblebee visitors declined after the first week and remained low until the final week. We detected interactions of phenology and water on pollinator visitor composition, in which plants subject to drought were the only group to experience a late-season resurgence in visits by solitary bees and flies. Despite that interaction, net reproductive success measured as seed production responded additively to the two manipulations of water and phenology. Commonly observed declines in flower size and reward due to drought or shifts in phenology may not necessarily result in reduced plant reproductive success, which in M. ciliata responded more directly to water availability. The results highlight the need to go beyond studying single responses to climate changes, such as either phenology of a single species or how it experiences an abiotic factor, in order to understand how climate change may affect plant reproductive success.

Root Secondary Metabolites in Populus tremuloides: Effects of Simulated Climate Warming, Defoliation, and Genotype

Climate warming can influence interactions between plants and associated organisms by altering levels of plant secondary metabolites. In contrast to studies of elevated temperature on aboveground phytochemistry, the consequences of warming on root chemistry have received little attention. Herein, we investigated the effects of elevated temperature, defoliation, and genotype on root biomass and phenolic compounds in trembling aspen (Populus tremuloides). We grew saplings of three aspen genotypes under ambient or elevated temperatures (+4-6 °C), and defoliated (by 75%) half of the trees in each treatment. After 4 months, we harvested roots and determined their condensed tannin and salicinoid (phenolic glycoside) concentrations. Defoliation reduced root biomass, with a slightly larger impact under elevated, relative to ambient, temperature. Elevated temperature decreased condensed tannin concentrations by 21-43% across the various treatment combinations. Warming alone did not alter salicinoid concentrations but eliminated a small negative impact of defoliation on those compounds. Graphical vector analysis suggests that effects of warming and defoliation on condensed tannins and salicinoids were predominantly due to reduced biosynthesis of these metabolites in roots, rather than to changes in root biomass. In general, genotypes did not differ in their responses to temperature or temperature by defoliation interactions. Collectively, our results suggest that future climate warming will alter root phytochemistry, and that effects will vary among different classes of secondary metabolites and be influenced by concurrent ecological interactions such as herbivory. Temperature- and herbivory-mediated changes in root chemistry have the potential to influence belowground trophic interactions and soil nutrient dynamics.

Effects of experimental watering but not warming on herbivory vary across a gradient of precipitation

Climate change can affect biotic interactions, and the impacts of climate on biotic interactions may vary across climate gradients. Climate affects biotic interactions through multiple drivers, although few studies have investigated multiple climate drivers in experiments. We examined the effects of experimental watering, warming, and predator access on leaf water content and herbivory rates of woolly bear caterpillars (Arctia virginalis) on a native perennial plant, pacific silverweed (Argentina anserina ssp. pacifica), at two sites across a gradient of precipitation in coastal California. Based on theory, we predicted that watering should increase herbivory at the drier end of the gradient, predation should decrease herbivory, and watering and warming should have positive interacting effects on herbivory. Consistent with our predictions, we found that watering only increased herbivory under drier conditions. However, watering increased leaf water content at both wetter and drier sites. Warming increased herbivory irrespective of local climate and did not interact with watering. Predation did not affect herbivory rates. Given predictions that the study locales will become warmer and drier with climate change, our results suggest that the effects of future warming and drying on herbivory may counteract each other in drier regions of the range of Argentina anserina. Our findings suggest a useful role for range-limit theory and the stress-gradient hypothesis in predicting climate change effects on herbivory across stress gradients. Specifically, if climate change decreases stress, herbivory may increase, and vice versa for increasing stress. In addition, our work supports previous suggestions that multiple climate drivers are likely to have dampening effects on biotic interactions due to effects in different directions, though this is context-dependent.

Emergent vulnerability to climate-driven disturbances in European forests

Forest disturbance regimes are expected to intensify as Earth’s climate changes. Quantifying forest vulnerability to disturbances and understanding the underlying mechanisms is crucial to develop mitigation and adaptation strategies. However, observational evidence is largely missing at regional to continental scales. Here, we quantify the vulnerability of European forests to fires, windthrows and insect outbreaks during the period 1979–2018 by integrating machine learning with disturbance data and satellite products. We show that about 33.4 billion tonnes of forest biomass could be seriously affected by these disturbances, with higher relative losses when exposed to windthrows (40%) and fires (34%) compared to insect outbreaks (26%). The spatial pattern in vulnerability is strongly controlled by the interplay between forest characteristics and background climate. Hotspot regions for vulnerability are located at the borders of the climate envelope, in both southern and northern Europe. There is a clear trend in overall forest vulnerability that is driven by a warming-induced reduction in plant defence mechanisms to insect outbreaks, especially at high latitudes.

Natural disturbances imperil healthy and productive forests, but quantifying their effects at large scales is challenging. Here the authors apply machine learning to disturbance records and satellite data to quantify and map European forest vulnerability to fires, windthrows, and insect outbreaks through 1979-2018.