Climate change-mediated temperature extremes and insects: From outbreaks to breakdowns

Understanding and counteracting the denial of insect biodiversity loss

Biodiversity loss is occurring globally with negative impacts on ecosystem function and human well-being. There is a scientific consensus that diverse environmental and anthropogenic factors are altering different components of insect biodiversity, with changes occurring at all levels of biological organisation. Here, we describe how uncertainty around specific trends and the semantics of 'decline' in relation to insect biodiversity have been leveraged by denialist campaigns to manufacture doubt around the insect biodiversity crisis. Disinformation is one of the biggest threats to social cohesion and environmental integrity globally. We argue that scientists, academic institutions, policymakers, and journalists must combat denialism by relying on robust research, supporting efforts to communicate scientific uncertainty more effectively, and build consensus on the global impacts of insect biodiversity loss.

Heat treatments to kill eggs of two invasive forest insects: Lycorma delicatula (Hemiptera: Fulgoridae) and Lymantria dispar (Lepidoptera: Erebidae)

The spotted lanternfly (Lycorma delicatula) and spongy moth (Lymantria dispar) are notorious invasive forest pests that are spread through human-mediated transport to invade new habitats. In this study, spotted lanternfly and spongy moth eggs were exposed to various temperature-exposure time (35 to 70 °C and 15 to 135 min) treatments in the laboratory. Spotted lanternfly egg masses were collected from various sites in 2022 and 2023, while the spongy moth egg masses were obtained from lab-reared colonies. Heat treatments were applied using an Isotemp microbiological incubator in the spring of 2023 and the spring and fall of 2024. No eggs of either species hatched when exposed to temperatures ≥ 60 °C for durations longer than 15 min. Spotted lanternfly egg hatch declined at temperatures ≥ 45 °C, while reduced hatch of spongy moth eggs was not observed until temperatures reached ≥ 50 °C. The season (spring or fall) in which the eggs were heat treated did not affect the hatch rate of spotted lanternfly eggs; however, spongy moth eggs were more vulnerable in the fall than in the spring. These findings suggest that heat treatment regimes that are already being used to kill insects in wood may effectively kill the eggs of both species on various substrates and that protocols for killing eggs at lower temperatures on more sensitive substrates may be possible by using longer-duration exposures.

Thermal modulation of insecticide-induced hormetic and oxidative responses in insect pests

Environmental global changes are dramatically affecting agroecosystems. Insects have been shown to present various responses to multi-stress conditions (i.e., increase in temperature and exposure to contaminants). However, there is a knowledge gap on how temperature can modulate the hormetic effects in individuals sublethally exposed to chemical stressors. Here, we investigated how temperature (15, 20, 25, and 28 °C) modulates the effects of lethal and sublethal exposure to insecticides (imidacloprid) on the longevity, fecundity, and oxidative stress of a pest insect, the aphid Mysus persicae. Our results showed additive and interactive effects of temperature and insecticide on the stimulatory and oxidative responses of the insect pest. Overall, imidacloprid was 2.4-fold less toxic at 15 °C (3.547 μg/ml) than at 20 °C (1.482 μg/ml) and 24.6 to 19.8-fold less toxic than at 25 °C (0.144 μg/ml) and 28 °C (0.179 μg/ml) respectively. Furthermore, although the exposure of female aphids to most sublethal concentrations resulted in a decrease in their longevity and fecundity compared to the control, some of the sublethal concentrations produced positive effects in these parameters for the exposed individuals. The magnitude of induced sublethal effects varied between temperatures and occurred in similar ranges of low concentrations at temperatures 15 °C and 20 °C, and at temperatures 25 °C and 28 °C. Additionally, imidacloprid low concentrations induced a temperature-dependent production of reactive oxygen species in exposed insects at 12 and 24 h after exposure indicating oxidative stress. Our study supplies valuable data on how temperature modulates pesticide-mediated hormesis that can alter ecological interactions and functions within agroecosystems with potential implications in pest management.

Life-history adaptation under climate warming magnifies the agricultural footprint of a cosmopolitan insect pest

Climate change is affecting population growth rates of ectothermic pests with potentially dire consequences for agriculture and global food security. However, current projection models of pest impact typically overlook the potential for rapid genetic adaptation, making current forecasts uncertain. Here, we predict how climate change adaptation in life-history traits of insect pests affects their growth rates and impact on agricultural yields by unifying thermodynamics with classic theory on resource acquisition and allocation trade-offs between foraging, reproduction, and maintenance. Our model predicts that warming temperatures will favour resource allocation towards maintenance coupled with increased resource acquisition through larval foraging, and the evolution of this life-history strategy results in both increased population growth rates and per capita host consumption, causing a double-blow on agricultural yields. We find support for these predictions by studying thermal adaptation in life-history traits and gene expression in the wide-spread insect pest, Callosobruchus maculatus; with 5 years of evolution under experimental warming causing an almost two-fold increase in its predicted agricultural footprint. These results show that pest adaptation can offset current projections of agricultural impact and emphasize the need for integrating a mechanistic understanding of life-history evolution into forecasts of pest impact under climate change.

Evaluating the Impact of Climate Change on the Asia Habitat Suitability of Troides helena Using the MaxEnt Model

Butterflies are highly sensitive to climate change, and Troides helena, as an endangered butterfly species, is also affected by these changes. To enhance the conservation of T. helena and effectively plan its protected areas, it is crucial to understand the potential impacts of climate change on its distribution. This study utilized a MaxEnt model in combination with ArcGIS technology to predict the global potential suitable habitats of T. helena under current and future climate conditions, using the species' distribution data and relevant environmental variables. The results indicated that the MaxEnt model provided a good prediction accuracy for the distribution of T. helena. Under the current climate scenario, the species is primarily distributed in tropical regions, with high suitability areas concentrated in tropical rainforest climates. In future climate scenarios, the suitable habitat areas for T. helena in medium and high suitability categories generally show an expansion trend, which increases over time. Especially under the SSP5-8.5 scenario, by the 2090s, the area of high suitability for T. helena is projected to increase by 42.85%. The analysis of key environmental factors revealed that precipitation of the wettest quarter (Bio16) was the most significant environmental factor affecting the distribution of T. helena. The species has high demands for precipitation and temperature and can adapt to future climate warming. This study is valuable for identifying the optimal conservation areas for T. helena and provides a reference for future conservation efforts.

Elevated Temperature Diminishes Reciprocal Selection in an Experimental Plant-Pollinator-Herbivore System

The geographic mosaic of coevolution predicts reciprocal selection, the first step in coevolution, to vary with changing biotic and abiotic environmental conditions. Studying how temperature affects reciprocal selection is essential to connect effects of global warming on the microevolutionary patterns of coevolution to the ecological processes underlying them. In this study, we investigated whether temperature influenced reciprocal selection between a plant (Brassica rapa) and its pollinating butterfly herbivore (Pieris rapae). In two temperature environments (ambient and hot), we measured the phenotypes of plants and butterflies, their interactions and fitness, which we used to calculate reciprocal selection. We found a variety of traits involved in reciprocal selection in the ambient environment, but none in the hot environment. We provide experimental evidence that elevated temperature weakens reciprocal selection, which will help better predict the consequences of global warming for coevolution.

Water deficit and aphid resilience on wheat: examining Sitobion avenae F. and their bacterial symbionts interplay under controlled laboratory conditions

BACKGROUND

Climate change has far-reaching effects on food security and agriculture, affecting crop yields and food distribution. Agriculture relies heavily on water for irrigation and production, making it vulnerable to water scarcity. Additionally, climate change can affect crop pest insects, leading to increased global crop losses, particularly in cereals, an important component of the human diet. Aphids are major crop pests and have a symbiotic relationship with bacterial endosymbionts that can contribute to their success as pests under a climate change scenario. To test the effect of drought on aphids, we examined varying levels of water deficit and endosymbiont composition on the grain aphid (Sitobion avenae) performance on wheat under controlled laboratory conditions. We measured the intrinsic rate of population increase (rm), the body weight of adult aphids, and the pre-reproductive period for different genotypes of the grain aphid (including Chilean superclones) under different irrigation regimes. We also analyzed the relative abundance of their endosymbionts under the different water treatments.

RESULTS

Our findings revealed that water deficit affects each aphid genotype differently, impacting various traits. For instance, the body weight of adult aphids was notably affected by different water treatments, with aphids grown under intermediate water deficit (IW) being significantly bigger. The relative abundance of endosymbionts also varied among genotypes and water treatments-specifically Regiella insecticola had a noticeably higher abundance under IW (P < 0.05).

CONCLUSION

This study provides valuable insights into the impact of water deficit on aphid performance and the role of endosymbionts in mitigating the effects of water deficit. © 2024 Society of Chemical Industry.

Short-term temperature changes affected the predation ability of Orius similis on Bemisia tabaci nymphs

Bemisia tabaci (Gennadius), a major pest that can adversely affect economies and agriculture globally, is particularly sensitive to climate change-induced temperature fluctuations, which can intensify its outbreaks. Orius similis Zheng, a primary natural predator of B. tabaci, also experiences temperature-related effects that influence its biocontrol efficacy. Thus, understanding the response of O. similis to temperature changes is pivotal for optimizing its biocontrol potential. Herein, our investigations showed that the functional response of O. similis to both high- and low-instar nymphs of B. tabaci adheres to the type II model at temperatures of 19, 22, 25, 28, and 31 °C. At 28 °C, O. similis exhibits the highest instantaneous attack rate (high-instar: 1.1580, low-instar: 1.2112), and the shortest handling time per prey (high-instar: 0.0218, low-instar: 0.0191). The efficacy of O. similis in controlling B. tabaci nymphs follows the sequence: 28 °C > 25 °C > 31 °C > 22 °C > 19 °C. Additionally, search efficiency inversely correlates with prey density. Simulations using the Hessell-Varley interference model indicate that increased density of O. similis under any temperature condition leads to reduced predation rates. Moreover, O. similis shows a predation preference for low-instar nymphs of B. tabaci, with higher predation level observed at the same temperature. In conclusion, for effective control of B. tabaci in field releases, O. similis should be optimally released at temperatures between 25 and 28 °C to preferably target the egg or early nymph stages of B. tabaci and determining the appropriate number of O. similis is important to minimize interference among individuals and enhance biocontrol efficacy.

Butterfly abundance changes in England are well associated with extreme climate events

Climate change exerts significant impacts on ecosystems through extreme climate events (ECEs), which are linked to various climate variables and can occur in different seasons. However, previous studies predominantly focus on a single type of ECE within specific seasons. We address this research gap by examining four typical types of ECEs: droughts, pluvials, heatwaves, and coldwaves, which are consistently defined and identified on a daily scale using a recently proposed statistical method. Butterflies in England serve as our study subject since their life stages occur throughout the year, and we had access to a 45-year dataset encompassing 57 butterfly species. First, we analyzed the correlation between abundance changes and the severity of ECEs, revealing varying sensitivity to ECEs across different life stages. Notably, abundance changes are negatively correlated with the severity of heatwaves in the hibernation, egg, and larval stages, as well as with the severity of pluvials in the larval, pupal, and adult stages. Second, we identified the most extreme climate events (MECEs) in England in the period from 1950 to 2020 and linked them with synchronized abundance changes for all species. MECEs in the sensitive stages of butterflies are frequently (for eight out of 11 MECEs) associated with synchronized decreases in their abundance. Our findings underscore the importance of considering diverse types of ECEs across all seasons to gain insights into their potential ecosystem effects. We draw attention to the fact that our analyses are primarily data-driven, with limited ecophysiological interpretation.

The Effects of Global Climate Warming on the Developmental Parameters of Helicoverpa armigera (Hübner, 1808) (Lepidoptera: Noctuidae)

Helicoverpa armigera (Hübner, 1808) is a significant global agricultural pest, particularly posing a major threat during the boll-forming stage of cotton. In recent years, the severity of its damage has increased markedly, and its population dynamics and biological characteristics may be profoundly affected by global climate change. This study conducted a systematic meta-analysis to evaluate the life history traits of H. armigera under conditions of rising global temperatures, different photoperiods, and humidity levels. A comprehensive analysis of 26 related studies revealed that different developmental stages of H. armigera have distinct temperature requirements. When the temperature is within an optimal range (32 °C to 35 °C), the development rate of H. armigera accelerates, the life cycle shortens, and the reproductive capacity of female moths increases. However, when the temperature exceeds 35 °C, development slows, mortality rates increase, and the oviposition of female moths decreases significantly, indicating a negative impact of high temperatures on growth and reproduction. Overall, as the temperature rises above 20 °C, various physiological indicators of H. armigera significantly improve, and at 32 °C, the larval development period and overall life cycle reach their shortest duration. This meta-analysis provides new insights into the biological responses of H. armigera in the context of climate change and offers a scientific basis for future control strategies.

A global overview of insect-fern interactions and its ecological trends

Historically, ferns have been described as underutilized by insects. However, studies have shown a diversity of insects interacting with ferns, although the evolutionary and ecological drivers of these interactions are still to be untangled. To fill these gaps, we compiled more than 100 yr of global data on insect-fern interactions from the literature comprising 374 fern and 649 insect species. With this database we assessed how fern trophic specialization, phylogenetic relationships and climate have shaped their interactions with insects. Our findings showed that interactions between ferns and insects can be explained by the phylogenetic relations among them. We observed that insect orders part of the Endopterygota clade tend to interact with similar fern species, which might be a result of the inheritance of Endopterygota ancestors probably due to phylogenetic niche conservationism. Under an ecological context, fern specialization increased with temperature, precipitation, and climatic stability. Our results show that climate might be one of the main factors explaining the spatial variation of insect-fern interactions, postulate also supported by the observed phylogenetic clustering of the studied ferns species. Our study highlights the intricate and multifaceted nature of insect-fern interactions, where evolutionary history and ecological factors converge to shape these relationships.

Ecological debts induced by heat extremes

Heat extremes have become the new norm in the Anthropocene. Their potential to trigger major ecological responses is widely acknowledged, but their unprecedented severity hinders our ability to predict the magnitude of such responses, both during and after extreme heat events. To address this challenge we propose a conceptual framework inspired by the core concepts of ecological stability and thermal biology to depict how responses of populations and communities accumulate at three response stages (exposure, resistance, and recovery). Biological mechanisms mitigating responses at a given stage incur associated costs that only become apparent at other response stages; these are known as 'ecological debts'. We outline several scenarios for how ecological responses associate with debts to better understand biodiversity changes caused by heat extremes.

Production of biodegradable food packaging from mango peel via enzymatic hydrolysis and polyhydroxyalkanoates synthesis: A review on microbial intervention

The rising environmental problem of plastic packaging waste has led to the development of sustainable alternatives, particularly for food packaging. Polyhydroxyalkanoates (PHAs) are biodegradable, thermoplastic polyesters. They are employed in the production of various products, including packaging films. The bio-based nature and appropriate features of PHAs, similar to conventional synthetic plastics, have garnered significant attention from researchers and industries. The current study aimed to produce biodegradable food packaging using mango peel (a major agricultural waste) with enzymatic hydrolysis and PHAs synthesis. Mango peel is the hub for macro-and micronutrients, including phytochemicals. The process includes an enzymatic hydrolysis step that converts complex carbohydrates into simple sugars using mango peel as a substrate. The produced sugars are used as raw materials for bacteria to synthesize PHAs, which are a class of biodegradable polymers produced by these microorganisms that can serve as packaging materials in the food industry. To solve environmental problems and increase the utilization of agricultural by-products, this review presents a practical method for producing food packaging that is environmentally friendly.

Improving multiple stressor-response models through the inclusion of nonlinearity and interactions among stressor gradients

Stressor-response models are used to detect and predict changes within ecosystems in response to anthropogenic and naturally occurring stressors. While nonlinear stressor-response relationships and interactions between stressors are common in nature, predictive models often do not account for them due to perceived difficulties in the interpretation of results. We used Irish river monitoring data from 177 river sites to investigate if multiple stressor-response models can be improved by accounting for nonlinearity, interactions in stressor-response relationships and environmental context dependencies. Out of the six models of distinct biological responses, five models benefited from the inclusion of nonlinearity while all six benefited from the inclusion of interactions. The addition of nonlinearity means that we can better see the exponential increase in Trophic Diatom Index (TDI3) as phosphorus increases, inferring ecological conditions deteriorating at a faster rate with increasing phosphorus. Furthermore, our results show that the relationship between stressor and response has the potential to be dependent on other variables, as seen in the interaction of elevation with both siltation and nutrients in relation to Ephemeroptera, Plecoptera and Trichoptera (EPT) richness. Both relationships weakened at higher elevations, perhaps demonstrating that there is a decreased capacity for resilience to stressors at lower elevations due to greater cumulative effects. Understanding interactions such as this is vital to managing ecosystems. Our findings provide empirical support for the need to further develop and employ more complex modelling techniques in environmental assessment and management.

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.

Experimental elevated temperature affects bumblebee foraging and flight speed

Global warming threatens wild bees and their interaction with plants. While earlier studies have highlighted the negative effects of elevated temperatures on bee-plant interactions, we still lack knowledge about how they impact the foraging behaviours that are central to bee pollination activities. To address this knowledge gap, we investigated how ambient temperature affected the foraging behaviours of the bumblebee Bombus terrestris. We allowed the bumblebees to forage freely on artificial flowers in two climate-controlled rooms set at 24°C and 32°C. The colonies were alternated between the two temperatures every week. We recorded the flower visitation rate, flight speed, total foraging time and number of foraging trips. In addition, we measured flight metabolic rate across a range of temperatures to assess its potential as an underlying mechanism. In comparison to 24°C, at 32°C, flower visitation time decreased while flower visitation rate and flight speed increased. This is consistent with the reduction in flight metabolic rate recorded between these temperatures. At 32°C, the number of trips made by each worker decreased, suggesting that, despite the reduced energetic cost, flight in elevated temperatures may be stressful. Our results suggest that elevated temperatures affect bumblebee foraging behaviour and that this would likely disrupt plant-insect interactions.

Heat waves during egg development alter maternal care and offspring quality in the European earwig

Climate change can disrupt animal fitness by reducing survival, fertility, fecundity and altering offspring development and survival. While parental care typically helps offspring cope with harsh environmental conditions, little is known about its role in buffering extreme temperature changes, such as heat waves. In this study, we tested whether parental care mitigates the impact of cold and heat waves on eggs and juveniles in the European earwig. In this insect, mothers provide obligatory egg care for about 50 days during winter, typically at temperatures around 10 °C. We exposed mothers and their eggs to three-day thermal waves of 3 °C, 10 °C (control), 17 °C or 24 °C, both 15 and 30 days after oviposition. We then measured four maternal care behaviors, maternal weight variation, as well as eggs' developmental time, survival, and hatching rate. In the resulting juveniles, we measured weight, developmental time, thermal resistance, and the expression of six heat stress and immunity genes. We found that thermal waves reduced maternal care and induced maternal weight gain. High temperatures also decreased egg hatching success, accelerated egg and nymph development, reduced the upper thermal limit of juveniles and decreased the expression of a heat shock protein (Hsp68), while other traits remained unaffected. Overall, this study highlights that access to maternal care is not enough to alleviate the stress of exposure to non-optimal temperatures during egg development in the European earwig. It also suggests that species with maternal care do not necessarily have access to effective thermal protection and may not be better adapted to climate change.

Climate change reduces elevational and latitudinal differences in spring phenology of pine caterpillar (Dendrolimus spectabilis Bulter)

The pine caterpillar (Dendrolimus spectabilis Bulter, Lepidoptera: Lasiocampidae), as an ectotherm, temperature plays a crucial role in its development. With climate change, earlier development of insect pests is expected to pose a more frequent threat to forest communities. Yet the quantitative research about the extent to which global warming affects pine caterpillar populations is rarely understood, particularly across various elevations and latitudes. Spring phenology of pine caterpillars showed an advancing trend with 0.8 d/10a, 2.2 d/10a, 2.2 d/10a, and 3.3 d/10a under the SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5 scenario, respectively. There was a maximum advance of 20 d in spring phenology of pine caterpillars during the 2090s, from mid-March to early March, and even late February. This study highlighted the significant advance in spring phenology at elevations >1000 m and lower latitudes. Consequently, the differences in elevational and latitudinal gradients were relatively small as the increasing temperatures at the end of the 21st century. And the average temperature in February-March was effective in explaining theses variability. These findings are crucial for adapting and mitigating to climate change.

Impact of high temperature and drought stress on the microbial community in wolf spiders

High temperatures and drought present significant abiotic challenges that can limit the survival of many arthropods, including wolf spiders, which are ectothermic and play a crucial role in controlling pest populations. However, the impact of these stress factors on the microbiota of spiders remains poorly understood. In this study, we utilized 16 S rRNA gene sequencing to explore the diversity and composition of bacterial communities within Pardosa pseudoannulata under conditions of high temperature and drought stress. We found that Firmicutes, Bacteroidetes, and Proteobacteria were the predominant bacterial phyla present. Analyses of alpha diversity indicated an increase in bacterial diversity under combined stress conditions, as reflected by various diversity indices such as Ace, Chao1, Shannon, and Simpson. Furthermore, co-occurrence network analysis highlighted intricate interactions among the microbial taxa (e.g., Enterobacter, Chitinophaga, and Eubacterium), revealing the adaptive complexity of the spider's microbiome to environmental stress. Functional prediction analysis suggested that combined stress conditions might enhance key metabolic pathways, particularly those related to oxidative phosphorylation and amino acid metabolism. Using Random Forest analysis, we determined that changes in three heat shock proteins were largely attributed to variations in bacterial communities, with Firmicutes being notably influential. Collectively, this in-depth analysis offers novel insights into the responses of microbial communities within spider microbiomes to combined abiotic stresses, providing valuable information for understanding extreme climate impacts and informing ecological management strategies.

Past, present and future of the two-spotted stink bug (Perillus bioculatus) in Europe revealed by citizen science

The introduction of the Nearctic predaceous stink bug species, (Perillus bioculatus) was attempted multiple times in various countries throughout Europe to mitigate the damage caused by the invasive and harmful pest species, the Colorado potato beetle (Leptinotarsa decemlineata). Though these attempts were thought to be unsuccessful for decades, more recent data elucidated that the species have established small self-sustaining populations in the Balkans Peninsula, Southern Russia, and Türkiye and recently began to expand. In the past years, the European range of the species reached Eastern Europe. After the first individuals were found in Hungary in October 2023 a citizen science campaign was launched to investigate the distribution of the species in the country. By June 2024 it became evident that the species is established throughout the country. Furthermore, observations regarding beetle larvae and moth caterpillars as alternative prey were reported supporting the previous assumptions that the naturalization and expansion of the species in Europe is facilitated by dietary drift. Here, we summarize the knowledge on the European presence of the two-spotted stink bug and formulate hypotheses regarding its future distribution and the impact of the species on the insect communities of the newly colonized areas.

Heat-stress memory enhances the acclimation of a migratory insect pest to global warming

In the face of rising global temperatures, the mechanisms behind an organism's ability to acclimate to heat stress remain enigmatic. The rice leaf folder, Cnaphalocrocis medinalis, traditionally viewed as temperature-sensitive, paradoxically exhibits robust larval acclimation to heat stress. This study used the heat-acclimated strain HA39, developed through multigenerational exposure to 39°C during the larval stage, and the unacclimated strain HA27 reared at 27°C to unravel the transgenerational effects of heat acclimation and its regulatory mechanisms. Heat acclimation for larvae incurred a fitness cost in pupae when exposed to high temperature, yet a significant transgenerational effect surfaced, revealing heightened fitness benefit in pupae from HA39, even without additional heat exposure during larval recovery at 27°C. This transgenerational effect exhibited a short-term memory, diminishing after two recovery generations. Moreover, the effect correlated with increased superoxide dismutase (SOD) enzyme activity and expression levels of oxidoreductase genes, representing physiological and molecular foundations of heat acclimation. Heat-acclimated larvae displayed elevated DNA methylation levels, while pupae from HA39, in recovery generations, exhibited decreased methylation indicated by the upregulation of a demethylase gene and downregulation of two methyltransferase genes at high temperatures. In summary, heat acclimation induces DNA methylation, orchestrating heat-stress memory and influencing the expression levels of oxidoreductase genes and SOD activity. Heat-stress memory enhances the acclimation of the migratory insect pest to global warming.

High-temperature responses of Myzus persicae and its parasitoid Aphidius gifuensis in relation to heat level, duration and developmental stage

BACKGROUND

Understanding how parasitoids respond to temperature is crucial for improving biological control strategies under the context of global warming. This study examined the suitability of Myzus persicae and its parasitoid Aphidius gifuensis to varying temperature conditions, as well as the stage-specific response of A. gifuensis to high temperatures.

RESULTS

High temperatures had a significant impact on the both M. persicae and A. gifuensis. When exposed to 36°C, M. persicae developed more slowly and produced smaller adults compared to control, regardless of the duration of exposure (2, 4 or 6 h); additionally, the survival rate of M. persicae nymphs sharply decreased under these conditions. Exposure to 36°C for 4 h negatively impacted the development of A. gifuensis. Female parasitoids exposed to 32°C developed into smaller adults, whereas males exposed to all three temperature levels were smaller compared to control group. Female parasitoids exposed to high temperatures, regardless of the specific heat level and duration, exhibited reduced longevity and decreased fecundity. None of the parasitoids exposed to 36°C for 6 h daily developed into adults. Heat treated during early developmental stages (2 and 4 days old) had a greater influence on parasitoid development, whereas heat treatment at 4 and 6 days old had a more significant impact on its fecundity.

CONCLUSION

High temperatures not only directly affected the performance of A. gifuensis, but also exerted indirect effects by influencing the quality of the host aphids M. persicae. The deleterious effects of high temperature on larvae can persist into the adult stage, affecting the longevity and reproduction of adults. These findings are important for the utilization of A. gifuensis in the control of M. persicae in warming environments. © 2024 Society of Chemical Industry.

Timing-dependent effects of elevated temperature on reproductive traits in the European corn borer moth

Elevated temperature often has life stage-specific effects on ectotherms because thermal tolerance varies throughout ontogeny. Impacts of elevated temperature may extend beyond the exposed life stage if developmental plasticity causes early exposure to carry-over or if exposure at multiple life stages cumulatively produces effects. Reproductive traits may be sensitive to different thermal environments experienced during development, but such effects have not been comprehensively measured in Lepidoptera. In this study, we investigate how elevated temperature at different life stages alters reproduction in the European corn borer moth, Ostrinia nubilalis. We tested effects of exposure to elevated temperature (28 °C) separately or additively during larval, pupal, and adult life stages compared to control temperatures (23 °C). We found that exposure to elevated pupal and adult temperature decreased the number of egg clusters produced, but exposure limited to a single stage did not significantly impact reproductive output. Furthermore, elevated temperature during the pupal stage led to a faster transition to the adult stage and elevated larval temperature altered synchrony of adult eclosion, either by itself or combined with pupal temperature exposure. These results suggest that exposure to elevated temperature during development alters reproduction in corn borers in multiple ways, including through carry-over and additive effects. Additive effects of temperature across life stages are thought to be less common than stage-specific or carry-over effects, but our results suggest thermal environments experienced at all life stages need to be considered when predicting reproductive responses of insects to heatwaves.

Temperature-Dependent Oviposition Models for Monochamus saltuarius (Coleoptera: Cerambycidae)

Monochamus saltuarius Gebler is a serious insect pest in Europe and East Asia regions, including Portugal, Spain, China, Japan, and Korea. It transfers the pine wood nematode Bursaphelenchus xylophilus to conifer trees, resulting in pine wilt disease (PWD). As temperature is a key factor influencing insect population dynamics, temperature-dependent models describing M. saltuarius oviposition could estimate population growth potential and evaluate outbreak risks. In this study, the longevity and fecundity of M. saltuarius females were measured under constant temperature conditions ranging from 20 to 32 °C, and temperature-dependent models were constructed. The longevity of M. saltuarius females ranged from 83.36 days to 22.92 days, with a total fecundity of 141 eggs and 52.77 eggs at 20 °C and 32 °C, respectively. To describe oviposition, we used a single-phase simulation describing oviposition as a single model and a two-phase simulation describing sexual maturation and oviposition as two separate models. These models effectively described M. saltuarius oviposition (r2 > 0.96) under constant temperature conditions, with the two-phase simulation demonstrating greater accuracy overall. Such models could facilitate assessments of PWD risks. The modeling framework of this study shows potential for predicting threats from various forestry and agricultural pests.

Response of wild aquatic insect communities to thermal variation through comparative landscape transcriptomics

Fluctuations in temperature are recognized as a potent driver of selection pressure, fostering genomic variations that are crucial for the adaptation and survival of organisms under selection. Notably, water temperature is a pivotal factor influencing aquatic organism persistence. By comprehending how aquatic organisms respond to shifts in water temperature, we can understand their potential physiological adaptations to environmental change in one or multiple species. This, in turn, contributes to the formulation of biologically relevant guidelines for the landscape scale transcriptome profile of organisms in lotic systems. Here, we investigated the distinct responses of seven stream stonefly species, collected from four geographical regions across Japan, to variations in temperature, including atmospheric and water temperatures. We achieved this by assessing the differences in gene expression through RNA-sequencing within individual species and exploring the patterns of community-genes among different species. We identified 735 genes that exhibited differential expressions across the temperature gradient. Remarkably, the community displayed expression levels differences of respiration and metabolic genes. Additionally, the diversity in molecular functions appeared to be linked to spatial variation, with water temperature differences potentially contributing to the overall functional diversity of genes. We found 22 community-genes with consistent expression patterns among species in response to water temperature variations. These genes related to respiration, metabolism and development exhibited a clear gradient providing robust evidence of divergent adaptive responses to water temperature. Our findings underscore the differential adaptation of stonefly species to local environmental conditions, suggesting that shared responses in gene expression may occur across multiple species under similar environmental conditions. This study emphasizes the significance of considering various species when assessing the impacts of environmental changes on aquatic insect communities and understanding potential mechanisms to cope with such changes.

Seasonality of forest insects: why diapause matters

Insects have major impacts on forest ecosystems, from herbivory and soil-nutrient cycling to killing trees at a large scale. Forest insects from temperate, tropical, and subtropical regions have evolved strategies to respond to seasonality; for example, by entering diapause, to mitigate adversity and to synchronize lifecycles with favorable periods. Here, we show that distinct functional groups of forest insects; that is, canopy dwellers, trunk-associated species, and soil/litter-inhabiting insects, express a variety of diapause strategies, but do not show systematic differences in diapause strategy depending on functional group. Due to the overall similarities in diapause strategies, we can better estimate the impacts of anthropogenic change on forest insect populations and, consequently, on key ecosystems.

Climate change, temperature extremes, and impacts on hyperparasitoids

Anthropogenic climate change, including temperature extremes, is having a major impact on insect physiology, phenology, behavior, populations, and communities. Hyperparasitoids (insects whose offspring develop in, or on, the body of a primary parasitoid host) are expected to be especially impacted by such effects due to their typical life history traits (e.g. low fecundity and slow development), small populations (being high on the food chain), and cascading effects mediated via lower trophic levels. We review evidence for direct and indirect temperature and climate-related effects mediated via plants, herbivores, and the primary parasitoid host species on hyperparasitoid populations, focusing on higher temperatures. We discuss how hyperparasitoid responses may feed back to the community and affect biological control programs. We conclude that despite their great importance, very little is known about the potential effects of climate change on hyperparasitoids and make a plea for additional studies exploring such responses.

Too hot to handle: temperature-induced plasticity influences pollinator behaviour and plant fitness

Increased temperature can induce plastic changes in many plant traits. However, little is known about how these changes affect plant interactions with insect pollinators and herbivores, and what the consequences for plant fitness and selection are. We grew fast-cycling Brassica rapa plants at two temperatures (ambient and increased temperature) and phenotyped them (floral traits, scent, colour and glucosinolates). We then exposed plants to both pollinators (Bombus terrestris) and pollinating herbivores (Pieris rapae). We measured flower visitation, oviposition of P. rapae, herbivore development and seed output. Plants in the hot environment produced more but smaller flowers, with lower UV reflectance and emitted a different volatile blend with overall lower volatile emission. Moreover, these plants received fewer first-choice visits by bumblebees and butterflies, and fewer flower visits by butterflies. Seed production was lower in hot environment plants, both because of a reduction in flower fertility due to temperature and because of the reduced visitation of pollinators. The selection on plant traits changed in strength and direction between temperatures. Our study highlights an important mechanism by which global warming can change plant-pollinator interactions and negatively impact plant fitness, as well as potentially alter plant evolution through changes in phenotypic selection.

Heat Stress and Plant-Biotic Interactions: Advances and Perspectives

Climate change presents numerous challenges for agriculture, including frequent events of plant abiotic stresses such as elevated temperatures that lead to heat stress (HS). As the primary driving factor of climate change, HS threatens global food security and biodiversity. In recent years, HS events have negatively impacted plant physiology, reducing plant's ability to maintain disease resistance and resulting in lower crop yields. Plants must adapt their priorities toward defense mechanisms to tolerate stress in challenging environments. Furthermore, selective breeding and long-term domestication for higher yields have made crop varieties vulnerable to multiple stressors, making them more susceptible to frequent HS events. Studies on climate change predict that concurrent HS and biotic stresses will become more frequent and severe in the future, potentially occurring simultaneously or sequentially. While most studies have focused on singular stress effects on plant systems to examine how plants respond to specific stresses, the simultaneous occurrence of HS and biotic stresses pose a growing threat to agricultural productivity. Few studies have explored the interactions between HS and plant-biotic interactions. Here, we aim to shed light on the physiological and molecular effects of HS and biotic factor interactions (bacteria, fungi, oomycetes, nematodes, insect pests, pollinators, weedy species, and parasitic plants), as well as their combined impact on crop growth and yields. We also examine recent advances in designing and developing various strategies to address multi-stress scenarios related to HS and biotic factors.

The impact of insect herbivory on biogeochemical cycling in broadleaved forests varies with temperature

Herbivorous insects alter biogeochemical cycling within forests, but the magnitude of these impacts, their global variation, and drivers of this variation remain poorly understood. To address this knowledge gap and help improve biogeochemical models, we established a global network of 74 plots within 40 mature, undisturbed broadleaved forests. We analyzed freshly senesced and green leaves for carbon, nitrogen, phosphorus and silica concentrations, foliar production and herbivory, and stand-level nutrient fluxes. We show more nutrient release by insect herbivores at non-outbreak levels in tropical forests than temperate and boreal forests, that these fluxes increase strongly with mean annual temperature, and that they exceed atmospheric deposition inputs in some localities. Thus, background levels of insect herbivory are sufficiently large to both alter ecosystem element cycling and influence terrestrial carbon cycling. Further, climate can affect interactions between natural populations of plants and herbivores with important consequences for global biogeochemical cycles across broadleaved forests.

Pest management facing warming and chemical stresses: Multi-stress effects on the biological agent Trichogramma oleae

Global change is affecting plant-insect interactions in agroecosystems and can have dramatic consequences on yields when causing non-targeted pest outbreaks and threatening the use of pest natural enemies for biocontrol. The vineyard agroecosystem is an interesting system to study multi-stress conditions: on the one hand, agricultural intensification comes with high inputs of copper-based fungicides and, on the other hand, temperatures are rising due to climate change. We investigated interactive and bottom-up effects of both temperature increase and copper-based fungicides exposure on the important Lepidopteran vineyard pest Lobesia botrana and its natural enemy, the oophagous parasitoid Trichogramma oleae. We exposed L. botrana larvae to three increasing copper sulfate concentrations under two fluctuating thermal regimes, one current and one future. Eggs produced by L. botrana were then exposed to T. oleae. Our results showed that the survival of L. botrana, was only reduced by the highest copper sulfate concentration and improved under the warmer regime. The development time of L. botrana was strongly reduced by the warmer regime but increased with increasing copper sulfate concentrations, whereas pupal mass was reduced by both thermal regime and copper sulfate. T. oleae F1 emergence rate was reduced and their development time increased by combined effects of the warmer regime and increasing copper sulfate concentrations. Size, longevity and fecundity of T. oleae F1 decreased with high copper sulfate concentrations. These effects on the moth pest and its natural enemy are probably the result of trade-offs between the survival and the development of L. botrana facing multi-stress conditions and implicate potential consequences for future biological pest control. Our study supplies valuable data on how the interaction between pests and biological control agents is affected by multi-stress conditions.

Silencing of catalase reduces unfavorable low-temperature tolerance capacity in whiteflies

BACKGROUND

Temperature is a primary factor that determines the eco-geographical distribution and population development of invasive insects. Temperature stress leads to various negative effects, including excess reactive oxygen species (ROS), and catalase (CAT) is a key enzyme against ROS in the antioxidant pathway. The whitefly Bemisia tabaci MED is a typical invasive pest that causes damage worldwide. Our previous studies have shown that CAT promotes whitefly adaptation to high temperature by eliminating ROS. However, the mechanism underlying the low-temperature adaptation of whiteflies is still unknown.

RESULTS

In this study, we investigated the role of CAT in the low-temperature tolerance of B. tabaci MED by analyzing its survival rate, reproduction, and ROS levels at 25 °C (as a control, suitable temperature), 20 °C (moderately decreased temperature), and 4 °C (severely decreased temperature). Silencing of BtCAT1, BtCAT2, or BtCAT3 reduced the viability of whiteflies under a short-term severely decreased temperature (4 °C), which manifested as decreases in survival and fecundity accompanied by significant increases in ROS levels. Moreover, even at a moderately decreased temperature (20 °C), silencing of BtCAT1 led to high ROS levels and low survival rates in adults.

CONCLUSION

Silencing of BtCATs significantly increased the sensitivity of B. tabaci MED to low temperatures. BtCAT1 is likely more essential than other BtCATs for low-temperature tolerance in whiteflies. © 2024 Society of Chemical Industry.

Predicting the fundamental thermal niche of ectotherms

Climate warming is predicted to increase mean temperatures and thermal extremes on a global scale. Because their body temperature depends on the environmental temperature, ectotherms bear the full brunt of climate warming. Predicting the impact of climate warming on ectotherm diversity and distributions requires a framework that can translate temperature effects on ectotherm life-history traits into population- and community-level outcomes. Here we present a mechanistic theoretical framework that can predict the fundamental thermal niche and climate envelope of ectotherm species based on how temperature affects the underlying life-history traits. The advantage of this framework is twofold. First, it can translate temperature effects on the phenotypic traits of individual organisms to population-level patterns observed in nature. Second, it can predict thermal niches and climate envelopes based solely on trait response data and, hence, completely independently of any population-level information. We find that the temperature at which the intrinsic growth rate is maximized exceeds the temperature at which abundance is maximized under density-dependent growth. As a result, the temperature at which a species will increase the fastest when rare is lower than the temperature at which it will recover from a perturbation the fastest when abundant. We test model predictions using data from a naturalized-invasive interaction to identify the temperatures at which the invasive can most easily invade the naturalized's habitat and the naturalized is most likely to resist the invasive. The framework is sufficiently mechanistic to yield reliable predictions for individual species and sufficiently broad to apply across a range of ectothermic taxa. This ability to predict the thermal niche before a species encounters a new thermal environment is essential to mitigating some of the major effects of climate change on ectotherm populations around the globe.

Thermal tolerance of mosquito eggs is associated with urban adaptation and human interactions

Climate change is expected to profoundly affect mosquito distributions and their ability to serve as vectors for disease, specifically with the anticipated increase in heat waves. The rising temperature and frequent heat waves can accelerate mosquito life cycles, facilitating higher disease transmission. Conversely, higher temperatures could increase mosquito mortality as a negative consequence. Warmer temperatures are associated with increased human density, suggesting a need for anthropophilic mosquitoes to adapt to be more hardy to heat stress. Mosquito eggs provide an opportunity to study the biological impact of climate warming as this stage is stationary and must tolerate temperatures at the site of female oviposition. As such, egg thermotolerance is critical for survival in a specific habitat. In nature, Aedes mosquitoes exhibit different behavioral phenotypes, where specific populations prefer depositing eggs in tree holes and prefer feeding non-human vertebrates. In contrast, others, particularly human-biting specialists, favor laying eggs in artificial containers near human dwellings. This study examined the thermotolerance of eggs, along with adult stages, for Aedes aegypti and Ae. albopictus lineages associated with known ancestry and shifts in their relationship with humans. Mosquitoes collected from areas with higher human population density, displaying increased human preference, and having a human-associated ancestry profile have increased egg viability following high-temperature stress. Unlike eggs, thermal tolerance among adults showed no significant correlation based on the area of collection or human-associated ancestry. This study highlights that the egg stage is likely critical to mosquito survival when associated with humans and needs to be accounted when predicting future mosquito distribution.

Responses of two Anastrepha species' immature stages infesting preferential hosts to different temperature exposures

Anastrepha fraterculus (Wiedemann) and A. obliqua (Macquart) are important pests of fruit crops. In Brazil, these species cause damage to fruit growing in the South (annual average temperature of 20.9 °C) and Northeast (average yearly temperature of 24 °C). We evaluated the effect of temperature on the viability and development time of A. fraterculus and A. obliqua immature stages in their respective preferred hosts, guava (Psidium guajava L., Myrtaceae) and mango (Mangifera indica L., Anacardiaceae). The duration of egg and pupal stages, egg to pre-pupa, and viability of egg and pupal stages under different temperatures (15, 20, 25, 30, and 35 °C) were assessed. For both species, development time decreased with increasing temperature. Viability in the evaluated stages was only observed between 15 and 30 °C. However, the species responded differently to the exposure temperatures (15 and 30 °C), especially in the pupal stage and from egg to pre-pupa. Anastrepha fraterculus showed a lower tolerance to high temperatures, especially in the pupal stage and from egg to pre-pupa, which may explain its lower importance and economic impact in warmer Brazilian regions. Anastrepha obliqua had a lower tolerance at 15 °C, indicating greater adequacy for temperatures above 20 °C, characteristic of Northeast Brazil, suggesting the capacity to spread to cooler areas with rising temperatures.

Sensitivity of Vanessa cardui to Temperature Variations: A Cost-Effective Experiment for Environmental Education

Temperature increases mediated through climate change threaten the survival of species. It is of foremost importance to engage citizens and future generations in understanding the mechanisms through which temperatures impose their effects. For educators, this is not straightforward, as tools for examining the impact of temperature over the lifetime of an animal are prohibitively expensive. At the same time, environmental educators need guidance on the appropriate study systems to use with a balance between the species having an obvious response and ensuring the outcomes are ethical and sustainable. In our study, we created and tested a cost-effective experiment meant to be used for environmental education purposes. More specifically, we tested the sensitivity of the painted lady butterfly Vanessa cardui to temperature variations using a homemade incubator. We describe the design of this experiment and report findings on survival rate, morphological variations, development time of various stages and wingspan of adults across a range of biologically relevant temperatures. The information provided gives educators options for testing a variety of hypotheses with regards to the impacts of temperature using an affordable and flexible set-up. Furthermore, the findings can be used by students to develop an understanding of the ramifications of the butterflies' responses in an ecological context.

Heatwave-like events affect drone production and brood-care behaviour in bumblebees

Climate change is currently considered one of the major threats to biodiversity and is associated with an increase in the frequency and intensity of extreme weather events, such as heatwaves. Heatwaves create acutely stressful conditions that may lead to disruption in the performance and survival of ecologically and economically important organisms, such as insect pollinators. In this study, we investigated the impact of simulated heatwaves on the performance of queenless microcolonies of Bombus terrestris audax under laboratory conditions. Our results indicate that heatwaves can have significant impacts on bumblebee performance. However, contrary to our expectations, exposure to heatwaves did not affect survival. Exposure to a mild 5-day heatwave (30-32 °C) resulted in increased offspring production compared to those exposed to an extreme heatwave (34-36 °C) and to the control group (24 °C). We also found that brood-care behaviours were impacted by the magnitude of the heatwave. Wing fanning occurred occasionally at temperatures of 30-32 °C, whereas at 34-36 °C the proportion of workers engaged in this thermoregulatory behaviour increased significantly. Our results provide insights into the effects of heatwaves on bumblebee colony performance and underscore the use of microcolonies as a valuable tool for studying the effects of extreme weather events. Future research, especially field-based studies replicating natural foraging conditions, is crucial to complement laboratory-based studies to comprehend how heatwaves compromise the performance of pollinators. Such studies may potentially help to identify those species more resilient to climate change, as well as those that are most vulnerable.

Thermal acclimation uncovers a simple genetic basis of adaptation to high temperature in a cosmopolitan pest

Understanding a population's fitness heterogeneity and genetic basis of thermal adaptation is essential for predicting the responses to global warming. We examined the thermotolerance and genetic adaptation of Plutella xylostella to exposure to hot temperatures. The population fitness parameters of the hot-acclimated DBM strains varied in the thermal environments. Using genome scanning and transcription profiling, we find a number of genes potentially involved in thermal adaptation of DBM. Editing two ABCG transporter genes, PxWhite and PxABCG, confirmed their role in altering cuticle permeability and influencing thermal responses. Our results demonstrate that SNP mutations in genes and changes in gene expression can allow DBM to rapidly adapt to thermal environment. ABCG transporter genes play an important role in thermal adaptation of DBM. This work improves our understanding of genetic adaptation mechanisms of insects to thermal stress and our capacity to predict the effects of rising global temperatures on ectotherms.

Body mass, temperature, and pathogen intensity differentially affect critical thermal maxima and their population-level variation in a solitary bee

Climate change presents a major threat to species distribution and persistence. Understanding what abiotic or biotic factors influence the thermal tolerances of natural populations is critical to assessing their vulnerability under rapidly changing thermal regimes. This study evaluates how body mass, local climate, and pathogen intensity influence heat tolerance and its population-level variation (SD) among individuals of the solitary bee Xenoglossa pruinosa. We assess the sex-specific relationships between these factors and heat tolerance given the differences in size between sexes and the ground-nesting behavior of the females. We collected X. pruinosa individuals from 14 sites across Pennsylvania, USA, that varied in mean temperature, precipitation, and soil texture. We measured the critical thermal maxima (CTmax) of X. pruinosa individuals as our proxy for heat tolerance and used quantitative PCR to determine relative intensities of three parasite groups-trypanosomes, Spiroplasma apis (mollicute bacteria), and Vairimorpha apis (microsporidian). While there was no difference in CTmax between the sexes, we found that CTmax increased significantly with body mass and that this relationship was stronger for males than for females. Air temperature, precipitation, and soil texture did not predict mean CTmax for either sex. However, population-level variation in CTmax was strongly and negatively correlated with air temperature, which suggests that temperature is acting as an environmental filter. Of the parasites screened, only trypanosome intensity correlated with heat tolerance. Specifically, trypanosome intensity negatively correlated with the CTmax of female X. pruinosa but not males. Our results highlight the importance of considering size, sex, and infection status when evaluating thermal tolerance traits. Importantly, this study reveals the need to evaluate trends in the variation of heat tolerance within and between populations and consider implications of reduced variation in heat tolerance for the persistence of ectotherms in future climate conditions.

Thirty-six years of butterfly monitoring, snow cover, and plant productivity reveal negative impacts of warmer winters and increased productivity on montane species

Climate change is contributing to declines of insects through rising temperatures, altered precipitation patterns, and an increasing frequency of extreme events. The impacts of both gradual and sudden shifts in weather patterns are realized directly on insect physiology and indirectly through impacts on other trophic levels. Here, we investigated direct effects of seasonal weather on butterfly occurrences and indirect effects mediated by plant productivity using a temporally intensive butterfly monitoring dataset, in combination with high-resolution climate data and a remotely sensed indicator of plant primary productivity. Specifically, we used Bayesian hierarchical path analysis to quantify relationships between weather and weather-driven plant productivity on the occurrence of 94 butterfly species from three localities distributed across an elevational gradient. We found that snow pack exerted a strong direct positive effect on butterfly occurrence and that low snow pack was the primary driver of reductions during drought. Additionally, we found that plant primary productivity had a consistently negative effect on butterfly occurrence. These results highlight mechanisms of weather-driven declines in insect populations and the nuances of climate change effects involving snow melt, which have implications for ecological theories linking topographic complexity to ecological resilience in montane systems.

Phenotypic plasticity of a winter-diapause mechanism copes with the effects of summer global warming in an ectothermic predator

To adapt to changes in temperature, animals tend to invest more energy in thermal tolerance to enhance survival, which can have simultaneous costs on plastic traits. Would a decrease in genetic variability, due to global warming, affect the ability of populations with existing metabolic regulatory mechanisms to cope with extreme temperatures? To address this question, we conducted a series of experiments based on the A1B scenario of global warming, assessing within-population genetic variance in (a) morphological traits, (b) metabolic rate allometries, and (c) survival of a winter-diapausing predator ectotherm. Our study focused on the lacewing species Chrysoperla pallida, using both exogamic and endogamic artificial genetic lines. We discovered that both lines use their winter-diapausing phenotype to adapt to summer extreme temperatures caused by extreme heating conditions, but the exogamic line is prone to express phenotypic plasticity in metabolic scaling, with a trade-off between body size and mandible size, i.e. larger individuals tended to develop smaller mandibles to better survive. These findings highlight the significance of substantial phenotypic plasticity and pre-existing metabolic regulatory mechanisms in enabling ectotherms to cope with potential extreme heating occurring in global warming.

The effects of temperature on prevalence of facultative insect heritable symbionts across spatial and seasonal scales

Facultative inheritable endosymbionts are common and diverse in insects and are often found at intermediate frequencies in insect host populations. The literature assessing the relationship between environment and facultative endosymbiont frequency in natural host populations points to temperature as a major component shaping the interaction. However, a synthesis describing its patterns and mechanistic basis is lacking. This mini-review aims to bridge this gap by, following an evolutionary model, hypothesizing that temperature increases endosymbiont frequencies by modulating key phenotypes mediating the interaction. Field studies mainly present positive correlations between temperature and endosymbiont frequency at spatial and seasonal scales; and unexpectedly, temperature is predominantly negatively correlated with the key phenotypes. Higher temperatures generally reduce the efficiency of maternal transmission, reproductive parasitism, endosymbiont influence on host fitness and the ability to protect against natural enemies. From the endosymbiont perspective alone, higher temperatures reduce titer and both high and low temperatures modulate their ability to promote host physiological acclimation and behavior. It is necessary to promote research programs that integrate field and laboratory approaches to pinpoint which processes are responsible for the temperature correlated patterns of endosymbiont prevalence in natural populations.

Temperature alters the toxicological impacts of plant terpenoids on the polyphagous model herbivore Vanessa cardui

Terpenes are a major class of secondary metabolites present in all plants, and long hypothesized to have diversified in response to specific plant-herbivore interactions. Herbivory is a major biotic interaction that plays out across broad temporal and spatial scales that vary dramatically in temperature regimes, both due to climatic variation across geographic locations as well as the effect of seasonality. In addition, there is an emerging understanding that global climate change will continue to alter the temperature regimes of nearly every habitat on Earth over the coming centuries. Regardless of source, variation in temperature may influence herbivory, in particular via changes in the efficacy and impacts of plant defensive chemistry. This study aims to characterize temperature-driven variation in toxicological effects across several structural classes of terpenes in the model herbivore Vanessa cardui, the painted lady butterfly. We observed a general increase in monoterpene toxicity to larvae, pupa, and adults at higher temperatures, as well as an increase in development time as terpene concentration increased. Results obtained from this study yield insights into possible drivers of seasonal variation in plant terpene production as well as inform effects of rising global temperatures on plant-insect interactions. In the context of other known effects of climate change on plant-herbivore interactions like carbon fertilization and compensatory feeding, temperature-driven changes in plant chemical defense efficacy may further complicate the prediction of climate change impacts on the fundamental ecological process of herbivory.

Host-Parasitoid Phenology, Distribution, and Biological Control under Climate Change

Climate change raises a serious threat to global entomofauna-the foundation of many ecosystems-by threatening species preservation and the ecosystem services they provide. Already, changes in climate-warming-are causing (i) sharp phenological mismatches among host-parasitoid systems by reducing the window of host susceptibility, leading to early emergence of either the host or its associated parasitoid and affecting mismatched species' fitness and abundance; (ii) shifting arthropods' expansion range towards higher altitudes, and therefore migratory pest infestations are more likely; and (iii) reducing biological control effectiveness by natural enemies, leading to potential pest outbreaks. Here, we provided an overview of the warming consequences on biodiversity and functionality of agroecosystems, highlighting the vital role that phenology plays in ecology. Also, we discussed how phenological mismatches would affect biological control efficacy, since an accurate description of stage differentiation (metamorphosis) of a pest and its associated natural enemy is crucial in order to know the exact time of the host susceptibility/suitability or stage when the parasitoids are able to optimize their parasitization or performance. Campaigns regarding landscape structure/heterogeneity, reduction of pesticides, and modelling approaches are urgently needed in order to safeguard populations of natural enemies in a future warmer world.

A Decade of Hidden Phytoplasmas Unveiled Through Citizen Science

Climate change is impacting agriculture in many ways, and a contribution from all is required to reduce the imminent losses related to it. Recently, it has been shown that citizen science could be a way to trace the impact of climate change. However, how can citizen science be applied in plant pathology? Here, using as an example a decade of phytoplasma-related diseases reported by growers, agronomists, and citizens in general, and confirmed by a government laboratory, we explored how to better value plant pathogen monitoring data. Through this collaboration, we found that in the last decade, 34 hosts have been affected by phytoplasmas; 9, 13, and 5 of these plants were, for the first time, reported phytoplasma hosts in eastern Canada, all of Canada, and worldwide, respectively. Another finding of great impact is the first report of a 'Candidatus Phytoplasma phoenicium'-related strain in Canada, while 'Ca. P. pruni' and 'Ca. P. pyri' were reported for the first time in eastern Canada. These findings will have a great impact on the management of phytoplasmas and their insect vectors. Using these insect-vectored bacterial pathogens, we show the need for new strategies that can allow fast and accurate communication between concerned citizens and those institutions confirming their observations.[Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Digestive enzyme activity and macromolecule content in the hemolymph of differentially adapted Lymantria dispar L. populations after short-term increases in ambient temperature

Global, unpredictable temperature increases have strong effects on all organisms, especially insects. Elucidating the effects of short-term temperature increases on midgut digestive enzymes (α-glucosidase, lipase, trypsin, and leucine aminopeptidase - LAP) and metabolic macromolecules in the hemolymph (proteins, lipids, and trehalose) of phytophagous pest larvae of Lymantria dispar is important for general considerations of insect adaptation to a warming climate and potential pest control options. We also wanted to determine whether the different adaptations of L. dispar populations to environmental pollution might affect their ability to cope with heat stress using larvae from the undisturbed, Kosmaj forest and disturbed, Lipovica forest. Heat treatments at 28 °C increased α-glucosidase activity in both larval populations, inhibited LAP activity in larvae from the polluted forest, and had no significant effect on trypsin and lipase activities, regardless of larval origin. The concentration of proteins, lipids, and trehalose in the hemolymph of larvae from the disturbed forest increased, whereas the population from the undisturbed forest showed only an increase in proteins and lipids after the heat treatments. Larval mass was also increased in larvae from the undisturbed forest. Our results suggest a higher sensitivity of digestive enzymes and metabolism to short-term heat stress in L. dispar populations adapted to pollution in their forest habitat, although climate warming is not beneficial even for populations from unpolluted forests. The digestive and metabolic processes of L. dispar larvae are substantially affected by sublethal short-term increases in ambient temperature.

Warmer temperatures reduce the transmission of a virus in a gregarious forest insect

Understanding how climate warming will influence species interactions is a key question in ecology and predicting changes in the prevalence of disease outbreaks is particularly challenging. Ectotherms are likely to be more influenced by climatic changes as temperature governs their growth, feeding, development, and behavior. We test the hypothesis that pathogen transmission and host mortality will increase at warmer temperatures using a cyclic forest insect, the western tent caterpillar (WTC), Malacosoma californicum pluviale, and its baculovirus. The virus causes population declines at peak host density. WTC are gregarious and clustering is predicted to increase the risk of within family infection; however, how temperature influences this has not been examined. We investigated the impact of temperature on different components of the transmission process in order to pinpoint the possible mechanisms involved. In the laboratory, leaf consumption increased linearly with rising temperature between 15 and 30°C. Insects died more rapidly from virus infection as temperature increased, but this did not translate into differences in the production of viral transmission stages. To examine the influence of temperature on virus transmission, we created a temperature difference between two greenhouses containing potted red alder trees, Alnus rubra. The cooler greenhouse (mean 19.5°C) was roughly similar to ambient temperatures in the field, while the warmer greenhouse was 10°C higher (mean 29°C). As predicted, both larval movement and feeding were higher at the warmer temperature, while the likelihood of the preinfected, inoculum larvae dying on the tents was twice as high in the cooler greenhouse. This resulted in increased virus mortality and a higher transmission parameter under cooler conditions. Therefore, we suggest that, contrary to our prediction, the reduced movement of infected larvae at colder temperatures increased the risk of infection in these gregarious insects and had a greater impact on virus transmission than the increased activity of the susceptible larvae in warmer conditions. Long-term population data from the field, however, show no relationship between temperature and infection levels, suggesting that local changes in virus transmission might not scale up to population infection levels.

Phylogeny-based assignment of functional traits to DNA barcodes outperforms distance-based, in a comparison of approaches

The full potential for using DNA barcodes for profiling functional trait diversity has yet to be determined in plants and animals; thus, we outline a general framework for quantifying functional trait diversity of insect community DNA and propose and assess the accuracy of three methods for achieving this. We built a novel dataset of traits and DNA barcodes for wild bees in China. An informatics framework was developed for phylogeny-based integration of these data and prediction of traits for any subject barcodes, which was compared with two distance-based methods. For Phylogenetic Assignment, we additionally conducted a species-level analysis of publically available bee trait data. Under the specimen-level dataset, the rate of trait assignment was negatively correlated with distance between the query and the nearest trait-known reference, for all methods. Phylogenetic Assignment was found to perform best under several criteria; particularly, it had the lowest false-positive rate (rarely returning a state prediction where success was unlikely; where the distance from query to the nearest reference was high). For a wider range of compiled traits, conservative life-history traits showed the highest rates of assignment; for example, sociality was predicted with confidence at 53%, parasitism at 44% and nest location at 33%. As outlined herein, automated trait assignment might be applied at scale to either barcodes or metabarcodes. With further compilation and databasing of DNA barcode and trait data, the rate and accuracy of trait assignment is expected to increase to the point of being a widely viable and informative approach.

Hot and cold waves decrease sperm production and bias sex ratio in the parasitoid wasp Cotesia typhae (Hymenoptera, Braconidae)

Parasitoid wasps are haplodiploid, meaning that sperm stored by egg laying females are only used to produce daughters. Thus, the sex ratio of the offspring depends on the availability of sperm after mating. In these insects, males are sensitive to temperature at the pupal stage. This stress leads to subfertility due to a drastic reduction in the number of sperm produced and transferred to females. Experiments were conducted under controlled conditions on the parasitoid wasp Cotesia typhae (Hymenoptera, Braconidae), a natural enemy of the invading pest Sesamia nonagrioides (Lepidoptera, Noctuidae). At 25-27 °C, sperm production was measured for 7 days, and found to reach a plateau at the third day of adult life. It leads to a final amount around 25,000 sperm per male. A male can successfully inseminate at least 10 females, producing predominantly female offspring. Sperm production decreased significantly after 1 day of pupal exposure to heat at 34 or 36 °C and 7 days of cold at 0, 5 or 10 °C. This highlights that both cold and heat are stressful. After mating with one male treated at 10 or 34 °C, females store fewer sperm than the control, and produce fewer daughters. The sex ratio of the offspring is male biased when males experienced temperature stresses during development, like other parasitoid wasps. In the field, C. typhae populations would be affected by heat and cold, at least at the pupal stage. This lowers overwintering risk in case this biological agent was introduced in Europe. This risk is both economical, as companies seek to establish costly continuous production to sell beneficial insects, and ecological as the introduced population would not settle in the ecosystem. Lastly, the transport and storage of this insect of agronomic interest would need to consider temperature variations to ensure successful application.