Survive a Warming Climate: Insect Responses to Extreme High Temperatures

Thermal Stress and Its Effects on the Gut Microbiome of Parthenium Beetles

The gut microbiota plays a vital role in nutrient and energy utilization, as well as in the host's ability to adapt its immune system to environmental changes. As a biological control agent for the invasive Parthenium weed, the Parthenium beetle Zygogramma bicolorata (Z. bicolorata) Pallister is often exposed to fluctuating temperatures, which may induce stress in its natural habitat. This study utilized 16S amplicon sequencing to explore the impact of temperature stress on the gut microbiome of Z. bicolorata under cold (15°C), control (27°C), and hot (35°C) conditions. A total of 11 bacterial phyla and 149 genera were identified, with Firmicutes, Proteobacteria, and Cyanobacteria being the most abundant. Temperature treatments significantly influenced the diversity of the gut microbiota, as evidenced by alpha diversity measures. Principal coordinate analysis further revealed substantial variations in microbiome composition across the different temperature conditions. Additionally, PICRUSt2 analysis suggested that the gut microbiota is linked to metagenomic functions related to amino acid and carbohydrate transport, inorganic ion metabolism, and cellular processes. Our findings suggest that thermal stress alters the gut microbiome of Parthenium beetles, offering new insights into how these beetles may have ecologically adapted to temperature fluctuations, while also highlighting the potential role of gut microbes in maintaining beetle health under environmental stress.

Cellular immune senescence in mosquitoes accelerates when the temperature is warmer

Mosquitoes are poikilotherms and ectotherms, so their body temperature is predicated by the temperature of their environment. As the temperature rises, development and metabolism quicken. At the same time, immune strength weakens with aging, a process called senescence. Aging can be characterized as a function of time (chronological age) or as a function of how well the body operates (physiological age), and we predict that warmer temperature decouples chronological and physiological aging, accelerating immune senescence. We evaluated how warmer temperature and aging interact to alter cellular immunity in the mosquito, Anopheles gambiae, by rearing them at three temperatures and quantifying the number of immune cells, called hemocytes, and their phagocytic activity at four ages. We discovered that the number of circulating hemocytes decreases with warmer temperature and aging, and that the aging-dependent decrease occurs faster when the temperature is warmer. However, the number of sessile hemocytes attached to the dorsal abdominal wall increases with infection and warmer temperature but decreases with aging. When a mosquito is infected, the aging-dependent decrease in the number of sessile hemocytes occurs faster when the temperature is warmer. Although the number of hemocytes decreases with aging, the phagocytic activity of individual hemocytes increases, with the aging-dependent increase occurring earlier when the temperature is warmer. Overall, warmer temperature accelerates senescence of the cellular immune response in mosquitoes, which has implications for how poikilotherms and ectotherms fight infections as they age in our warming world.

Genome-Wide Identification and Functional Characterization of Brown Spot Resistance Genes in Rice (Oryza sativa L.)

Rice brown spot (BS) caused by Cochliobolus miyabeanus affects both rain-fed and upland rice production, causing both yield and grain quality loss. Here, we used a genome-wide association study (GWAS) to analyze the resistance of 130 rice cultivars to BS disease. We identified two quantitative trait loci on chromosome 4. We screened three candidate genes using two kinds of RNA-seq data, LD block, Gene Ontology, Kyoto Encyclopedia of Genes and Genomes databases (KEGG), and reverse transcription-quantitative polymerase chain reaction. To further identify the candidate gene function, we constructed transgenic lines to verify the gene resistance functions against C. miyabeanus. The gene function research about the overexpression lines of OsExo70F3 and OsBSR820 and the Osmed30 gene function loss T-DNA lines showed more resistance to BS than their wildtypes. The exo70 and Med gene families reportedly participate in abiotic stress in rice, and OsBSR820 is a novel functional gene detected in GWAS-based studies. Subcellular localization results also showed that these genes were located in the cellular sites associated with plant immunity. This is the first study to use GWAS to locate BS resistance genes and to identify the function of genes. We believe that this study will provide valuable insights for exploring additional BS disease resistance-related genes in the future.

Function of SfDNAJA1 and SfHSP68 in Temperature Stress Response and Apoptosis in Fall Armyworm (Spodoptera frugiperda)

The fall armyworm (Spodoptera frugiperda) is a major invasive pest. To explore its adaptive mechanisms under temperature stress, we conducted transcriptome analysis across six developmental stages and both sexes at 0, 26, and 46 °C. High-temperature stress induced more differentially expressed genes (DEGs, 8,703) than low-temperature stress (5,426), with fourth instar larvae showing the most DEGs at low temperatures. Sex-specific responses were also evident. Sixteen heat shock protein (HSP) genes and 31 apoptosis-related genes were identified as key stress-responsive factors. RNAi knockdown of SfDNAJA1 and SfHSP68 reduced survival under temperature stress, increased ROS and Cyt c levels, and upregulated apoptosis-related genes, while ATP levels decreased. Elevated caspase-3, G6PD, and GST activities further indicated oxidative and apoptotic responses. These results underscore the essential role of HSPs in maintaining cellular homeostasis and regulating apoptosis during thermal stress, offering insights into pest adaptation and potential control strategies.

Pot-pollen DNA barcoding as a tool to determine the diversity of plant species visited by Ecuadorian stingless bees

Identifying the main species of plants from where Ecuadorian stingless bees collect pollen is one of the key objectives of management and conservation improvement for these insects. This study aims to determine the botanical origin of pot-pollen using two barcodes, comparing two methodologies (DNA barcoding versus electron microscopy and morphometric tools) and determine the genus and species of pollen source plants of the main honey-producing stingless bees in Ecuador. As main results, Prockia crucis, Coffea canephora, Miconia nervosa, Miconia notabilis, Laurus nobilis, Cecropia ficifolia, Theobroma sp., Artocarpus sp., Croton sp., Euphorbia sp., Mikania sp., and Ophryosporus sp., were the genera and species with the highest presence in the nests (n = 35) of three genera of stingless bees of two provinces located in different climatic regions inside the continental Ecuador. Plant species richness in both areas was statistically similar (p-value = 0.21). We concluded that floral sources' molecular identification with the ITS2 region had a higher number of genera and species detected, than the rbcL gene and microscopy tools, for the Ecuadorian landscapes. We confirmed that the foraging behavior of Melipona sp., Scaptotrigona sp., and Tetragonisca sp., could include non-native flora (27%, 12/44 identifications) that provide a rich source of pollen. Stingless beekeepers could use this information to create flower calendars and establish a schedule for better management of stingless bees in secondary and modified environments.

Dynamic interplay between niche variation and flight adaptability drove a hundred million years' dispersion in iconic lacewings

The form and change of animal biogeography reflects the long-term interplay between organisms and their environment, involving physiological limitation, dispersal capability, and adaptive evolution versus plate tectonics, global climatic shifts, and changing landscapes. This is especially manifest for lineages with extended geological histories, which, therefore, evokes questions as to the associated processes producing such patterns. Insects, as the earliest flying animals, have exceptional abilities for expanding their range and habitats and to avoid detrimental conditions. They are ideal for exploring historical biogeography augmented via adaptation. Here, we employ beaded lacewings as a model to explore such patterns and likely processes, particularly given that they differ notably from the commonly observed pattern of a latitudinal diversity gradient. Furthermore, owing to their good fossil record it can be observed that their distributions varied remarkably through time. Ecological niche modeling and evaluation demonstrate their niche variation and niche breadth expansion intermittently accompanying global climate change. However, different niche relevant variables changed under patterns of either phylogenetic conservatism or evolutionary lability. By assessing wing morphological disparity and modeling flight aerodynamics, we uncovered a continuous improvement of flight efficiency through beaded-lacewing history as well as a Paleogene divergence in strategy, which reveals a long-term associated path with the niche variation. Our results unveil the adaptive evolution and dispersal history of beaded lacewings through 170 My, achieved by dynamic strategies in niche shift and flight adaptation as responses to a changing planet.

Assessing the potential global distribution of Monochamus sutor (Coleoptera: Cerambycidae) under the influence of climate change and human activities based on Maximum Entropy model

Monochamus sutor, an important phytophagous pest, is a known vector insect of Bursaphelenchus mucronatus in addition to feeding directly on trees. Although B. mucronatus causes relatively minor damage in European and Asian forests, its threat to coniferous forests is similar to that of Bursaphelenchus xylophilus. Given that B. xylophilus evolved into a destructive pathogen after its introduction into Asia, B. mucronatus may also pose a potential threat to North American coniferous forests. Therefore, we assessed the potential global distributions areas of M. sutor and their relative dynamics under different climate scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) in the current (i. considering only bioclimatic factors; ii. including anthropogenic factors) and in the future (2050s and 2070s) using an optimized Maximum Entropy ecological niche model. The mean area under the curve value of the optimized model was greater than 0.86 and the true skill statistic value was greater than 0.79. Potentially suitable habitat for M. sutor is driven by a combination of temperature (Bio1 and Bio2), precipitation (Bio14, Bio15, and Bio18), and human activities. In the current period, suitable areas are concentrated in Europe, East Asia, and North America, and are smaller in the presence of anthropogenic disturbance than in the presence of bioclimatic factors alone. At the same time, under future climate scenarios, the potential range of M. sutor will always expand more than contract, with a projected increase of 1,329.02 to 1,798.23 × 104 km2 compared to the current time period, especially spread toward Canada and the United States of America in North America. The present study provides important insights into the potential risks of M. sutor, which is important to help guide decision-making in pest control as well as forest conservation.

Changes in Metabolomics Profiles of Propylea japonica in Response to Acute Heat Stress

The ladybird beetle, Propylea japonica Thunberg (Coleoptera: Coccinellidae), is a widely distributed natural predator that is crucial in controlling various agricultural pests in China. Despite frequent references to its remarkable thermotolerance, the molecular mechanisms underlying its thermotolerance remain poorly understood. Here, we investigated metabolomic changes in P. japonica following exposure to acute heat stress (AHS) lasting 1 h at 39 °C and 43 °C in populations from Zhengzhou (ZZ, warm temperate climate zone) and Shenzhen (SZ, subtropical climate zone), representing distinct northern and southern Chinese ecosystems. A total of 4165 and 4151 metabolites were detected in positive and negative ion modes, respectively. The high proportion of lipid and lipid-like metabolites (35.5%) and the top 20 pathways containing the highest number of metabolites, implying membrane fluidity modulation and energy metabolism restructuring, served as the core adaptive mechanism in P. japonica populations confronting thermal stress. The SZ25 vs. SZ39 exhibited a significantly higher number of differentially expressed metabolites (DEMs), which were predominantly enriched in the purine and tryptophan metabolism pathways. This indicated that these pathways orchestrate thermal adaptation in the SZ population by coordinating energy metabolism reprogramming, orchestrating antioxidant defense mechanisms, and modulating neuroendocrine homeostasis dysregulation. Additionally, the starch and sucrose, arachidonic acid, and fructose and mannose metabolism pathways were also implicated. This study enhances our understanding of P. japonica thermotolerance and provides a valuable reference for thermotolerance mechanisms in other insects.

Warmer temperatures reinforce negative land-use impacts on bees, but not on higher insect trophic levels

Climate and land-use change are major drivers of insect decline, yet their interactive effects on insect richness and abundance, especially across trophic levels, remain poorly understood. Here, we investigate how temperature and land use shape insect communities across spatial scales and trophic levels, from flowering plants and cavity-nesting bees to hunting wasps, their antagonists and parasitism rates. Using trap nests and a space-for-time approach, we surveyed 179 plots spanning four habitat types (forest, grassland, arable land and settlements) across 60 study regions in Germany covering semi-natural, agricultural and urban landscapes. Bee richness and abundance responded to climate-land-use interactions across spatial scales, being higher with warmer local daytime temperatures and overall warmer climates, but only in less intensive land uses. In contrast, elevated night-time temperatures negatively affected bees. Higher trophic levels benefited more consistently from warmer climates than lower trophic levels and were less affected by high local daytime and night-time temperatures. Parasitism rates were lowest in arable land but similar across habitats within semi-natural regions, suggesting that landscape-scale processes buffer local effects. Our findings underscore the importance of considering night-time temperatures for diurnal insects and suggest that rising temperatures may exacerbate the negative impacts of land use on pollinators.

Effects of temperature, relative humidity, and photoperiod on life history of Cotesia ruficrus (Hymenoptera: Braconidae), an indigenous parasitoid of Spodoptera frugiperda (Lepidoptera: Noctuidae)

The indigenous parasitoid Cotesia ruficrus (Haliday) (Hymenoptera: Braconidae) shows promise as a biological control agent for managing the invasive fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) in China. However, the influence of environmental factors on C. ruficrus performance remains poorly understood. This study aimed to investigate the effects of temperature, relative humidity, and photoperiod on the life history of C. ruficrus. The life-history traits were measured at 5 different temperatures (20, 23, 26, 29, and 32 ± 1 °C), 4 RH levels (40%, 55%, 70%, and 85 ± 5%), and 5 photoperiod levels (L:D 8:16, 10:14, 12:12, 14:10, and 16:8). As temperature increased from 20 to 32 °C, the immature developmental duration (from 19.8 to 11.0 d), egg load (from 263.8 to 100.8), adult size (from 0.75 and 0.72 to 0.66 and 0.65 mm for female and male, respectively), and longevity (from 28.43 and 24.98 to 5.03 and 5.3 d for female and male, respectively) significantly reduced, while parasitism rates remained stable (56.8% to 66.3%) but emergence rates decreased above 26 °C (from 93% to 75%). Higher RH (>70%) improved emergence rates (87% to 93%), sex ratios (0.63), egg load (278), and longevity (above 10 d for male and 14 d for female), with no significant effect on parasitism rates (65% to 69%). The highest parasitism rate (65%), sex ratio (0.63), and egg load (278) occurred under 14:10 photoperiod, with emergence rates (81% to 87%) unaffected by photoperiod changes. Collectively, optimal conditions for C. ruficrus development and reproduction were identified as 26 ± 1 °C temperature, 14:10 photoperiod, and above 70% RH.

A natural gene on-off system confers field thermotolerance for grain quality and yield in rice

Rising global temperatures threaten crop grain quality and yield; however, how temperature regulates grain quality and how to achieve synergistic thermotolerance for both quality and yield remain unknown. Here, we identified a rice major locus, QT12, which negatively controls grain-quality field thermotolerance by disrupting endosperm storage substance homeostasis through over-activating unfolded protein response (UPR). Natural variations in QT12 and an NF-Y complex form a natural gene on-off system to modulate QT12 expression and thermotolerance. High temperatures weaken NF-YB9/NF-YC10 interactions with NF-YA8, releasing QT12 suppression and triggering quality deterioration. Low QT12 expression confers superior quality and increases elite rice yield up to 1.31-1.93 times under large-scale high-temperature trials. Two trait regulatory haplotypes (TRHs) from co-selected variations of the four genetically unlinked genes in NF-Ys-QT12 were identified for subspecies thermotolerance differentiation. Our work provides mechanistic insights into rice field thermotolerance and offers a proof-of-concept breeding strategy to break stress-growth and yield-quality trade-offs.

Experimental short-term heatwaves negatively impact body weight gain and survival during larval development in Bombus terrestris L. (Hymenoptera: Apidae)

Climate change-induced heatwaves threaten global biodiversity, including crucial pollinators like bumblebees. In particular, the increasing frequency, duration and intensity of heatwaves is alarming. Despite these projections, little is known about the effects of short-term heatwaves on insect larval development. Hence, we investigated the impact of simulated heatwaves on the development of 4th instar larvae (L4) of Bombus terrestris L. (Hymenoptera: Apidae) using an in vitro rearing method. Individual larvae were incubated at 37°C and 38°C for a period of 4 days, with a constant rearing temperature of 34°C as the control. We examined body weight gain, developmental duration, survival to adult stage, and adult body size (i.e. dry mass, intertegular distance, and head width). A simulated heatwave of 37°C did not significantly affect larval development, but 38°C impaired larval body mass gain. While developmental duration and adult body size were unaffected, an acute heat stress of 38°C during the L4 stage reduced the probability of pupae reaching adulthood. These findings highlight the potential for heatwaves to negatively affect bee populations by impairing larval growth and reducing survival to the adult stage, which may have severe implications for colony fitness.

Climate influences broadly, landscape influences narrowly: Implications for agricultural beneficial insects

Insects provide critical ecosystem services, like pollination, in both natural and agricultural ecosystems. Delivery of these services depends on their ability to develop, survive, and move through their environment. Whether they can do this depends on the weather, climate, and landscape; but a changing climate means these systems are potentially vulnerable to disruption. Short-term fluctuations in weather can disrupt development, impede movement, and affect survival, while long-term climate norms influence environmental niches and influence species distribution. Landscape composition also influences beneficial insect distribution and has the potential to reduce the impacts of climate change. Here we use a database of >97,000 bee occurrence records, collected from 320 sampling sites across a 90,000+ km2 area in the North American Prairies to generate models of species occurrence for 50 species, sampling in and around crop fields. We use a tree-based machine learning method with extreme gradient boosting to create predictive classification models. These models are then used to analyze the relative importance of weather, climate, and landscape variables. The variables with the highest mean absolute importance are cumulative degree days, cumulative precipitation, and percent tree cover. When we analyzed individual species models, bee taxonomic groups responded most strongly to weather, and the direction of response corresponded to trait-grouping. The responses to landscape were weak and species-specific. The results indicate that pollination service supply is largely determined by heat and moisture, and that cavity nesters and ground-nesters have opposite responses to rising temperature, which could impact taxonomic and functional diversity.

A zinc finger protein shapes the temperature adaptability of a cosmopolitan pest

Global climate change is characterized by increased extreme temperatures affecting insects at all trophic levels. Zinc finger proteins (ZFPs) are key regulators of gene expression and cell differentiation in eukaryotes, essential for stress resistance in both animals and plants. Using CRISPR/Cas9 for gene deletion, this study predicted and examined the structure of ZFP320 in the diamondback moth (Plutella xylostella) and investigated its function in temperature stress response through a comprehensive age-stage, two-sex life table analysis. We found ZFP320 encodes a 387 amino acid protein (43 kDa) with no transmembrane domains, featuring a ZnF-C2H2 domain. Quantitative fluorescence analysis showed that ZFP320 expression increased under high temperatures. ZFP320 knockout altered antioxidant gene expression, resulting in higher levels of superoxide dismutase and catalase in mutant strains compared with wild-type strain. Life table analysis revealed that the mutant strains had shorter fecundity and oviposition periods under both normal and high temperatures. Additionally, mutant strains exhibited lower parameters (r, λ, R0), as well as reduced survival rates and critical thermal maxima. Notably, PxZFP320 plays a crucial role in temperature adaptation, paving the way for future investigations on the significance of ZFPs in P. xylostella's temperature tolerance.

Integrated mRNA and miRNA Omics Analyses Reveal Transcriptional Regulation of the Tolerance Traits by Aquatica leii in Response to High Temperature

Within the context of global warming, understanding the molecular mechanisms behind physiological plasticity and local adaptation is essential for insect populations. This study performed an integrated miRNA and mRNA analysis on Aquatica leii larvae exposed to temperatures of 20 °C, 24 °C, 28 °C, and 32 °C. Under varying thermal conditions, 1983 genes exhibited differential expression (i.e., DEGs). These genes showed significant enrichment in Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to carbohydrate metabolism, glycan biosynthesis and metabolism. Notably, we detected that the "neuroactive ligand-receptor interaction" signaling pathway, which is involved in environmental information processing, was significantly upregulated in the 28 °C and 32 °C treatment groups. This indicates that starting at 28 °C, A. leii needs to maintain normal cellular physiological functions by regulating ligand-receptor binding and signal transduction. Furthermore, 220 differentially expressed miRNAs (DEMs) were detected under the different temperature treatment conditions. An interaction network was constructed between key DEMs and DEGs, revealing 12 significant DEM-DEG regulatory pairs in A. leii under different temperature treatments. We found three miRNA-mRNA candidate modules that could be involved in A. leii's response to high temperature, including ggo-miR-1260b and ptr-miR-1260b/RN001_010114, CM069438.1_43851/RN001_014852, and CM069438.1_43851/RN001_014877. Our data provide deeper insights into the molecular responses of A. leii to the high temperature at the miRNA and mRNA levels.

Metabolic responses provide insight into interspecific variation in heat tolerance of three co-existing pest aphid species

Global warming leads to an increase in extreme heat events, posing significant challenges for insects. Sitobion avenae, Metopolophium dirhodum and Rhopalosiphum padi are important co-existing aphid species known to cause damage to cereal crops worldwide. The three species differ in thermal tolerance, with R. padi being much more heat tolerant than the other two species. However, it remains unclear whether interspecific variation in heat tolerance is due to differences in metabolic responses to heat stress. Here, we compared their metabolic signatures during and after recovery from the same injury level of heat stress (at 34°C for half and full durations to cause 50% mortality in each species), as well as the identical duration of heat stress. Using quantitative GC-MS, we found that after the same injury level of heat exposure, the three species showed similar changes in most metabolites. However, the heat-tolerant species, R. padi, had higher levels of polyols and amino acids, and uniquely accumulated glycerol. In addition, after the same duration of heat exposure, R. padi maintained a relatively stable metabolic profile, while the less tolerant species showed marked alterations with a shift from aerobic to anaerobic metabolism. We suggest that polyols and amino acids play a pivotal role in protecting R. padi from heat damage, contributing to its superior thermal tolerance. Overall, this comparative metabolomics study provides insight into the relationship between metabolic responses and heat tolerance of co-existing species, which helps understanding of the underlying mechanism of heat tolerance.

Effects of Feeding Sources and Different Temperature Changes on the Gut Microbiome Structure of Chrysomya megacephala (Diptera: Calliphoridae)

Chrysomya megacephala (Diptera: Calliphoridae), commonly referred to as the oriental latrine fly, is a synanthropic blowfly species frequently associated with decomposing organic matter. This study sought to investigate the influence of various feeding substrates and temperature conditions, specifically constant temperatures of 15, 25, 35 °C, and variable temperatures averaging 23.31 °C, on the gut microbiome of C. megacephala. The microbiome analysis was conducted using the Illumina HiSeq platform for 16S rRNA gene sequencing in Changsha, China. Across all experimental conditions, the gut microbiome of C. megacephala yielded 1257 operational taxonomic units (OTUs), which were categorized into 26 phyla, 72 classes, 165 orders, 270 families, 516 genera, and 794 species. The study showed significant differences in the gut microbiome of C. megacephala between different feeding sources and temperature conditions across the lifespan. Low temperature had the potential to reduce the proportion abundance of bacterial communities in the gut microbiome, while high and variable temperature increased them. Metabolism was the main predicted function with diverse phenotypic characters in the gut microbiota of C. megacephala. The presence of diverse bacterial phenotypes in the gut microbiome of C. megacephala highlights its significant interest for medicine and offers promising applications in industry and agriculture.

Effects of Temperature and Humidity on the Fitness of Aphid Parasitoid, Binodoxys communis

Binodoxys communis is a dominant endoparasitoid of aphids in cotton fields, yet empirical evidence on how temperature and humidity regulate its growth, development, and reproduction remains limited. To address this gap, we assessed the effects of both constant and fluctuating temperature, as well as various combinations of temperature and humidity, on the longevity, parasitism, and fecundity of this parasitoid. Our results revealed that adult longevity of B. communis was longer at 20 °C and 25 °C while significantly shortened at a high temperature (35 °C). Similarly, the parasitism rate, female ratio, emergence duration, and offspring longevity of the parasitoid were all superior at 20 °C and 25 °C compared to 15 °C and 35 °C. Moreover, the longevity of both male (6.96 ± 0.10 d) and female (6.88 ± 0.07 d) parasitoids was significantly extended at 25 °C and 60% RH. Temperature had a marked impact on the parasitic capability of parasitoids, with the number of Aphis gossypii parasitized daily by B. communis being significantly higher at 25 °C than at 15 °C and 35 °C. Nevertheless, humidity and the interaction between humidity and temperature had no significant influence on parasitic capacity. The parasitism of B. communis followed the Holling-II model, with the highest daily maximum parasitism observed at 25 °C. In conclusion, our study showed that 25 °C positively enhanced the fitness of B. communis, providing a valuable reference for indoor population expansion and field release of B. communis, potentially enhancing its effectiveness as a biological control agent against aphids.

Heat stress effects on offspring compound across parental care

Heatwaves associated with climate change threaten biodiversity by disrupting behaviours like parental care. While parental care may buffer populations from adverse environments, studies show mixed results, possibly due to heat stress affecting different care components. We investigated how heat stress impacts parental care and offspring performance in the burying beetle Nicrophorus nepalensis under control (17.8°C) and heat stress (21.8°C) conditions. We focused on two critical periods: pre-hatching care (carcass preparation) and post-hatching care (offspring provisioning). To disentangle the vulnerability of these parental care components to heat stress, we reciprocally transferred carcasses prepared under control or heat stress to females breeding under both conditions. Heatwaves affecting only one care period did not alter reproduction, but when both pre- and post-hatching periods experienced heatwaves, reproductive success declined. Females exhibited higher energy expenditure during provisioning, evidenced by greater body mass loss. Notably, heat stress had long-lasting effects on offspring via carcass preparation, resulting in smaller adult size and higher mortality. These results highlight the complexity of environmental stressors on parental care, suggesting that different care components may respond differently to heat stress, and thus need to be examined separately to better understand how parental care responds to, and buffers against, temperature stress.

Differential genome-wide expression profiles in response to high temperatures in the two body-color morphs of the pea aphid

Global warming and extremely high temperatures affect insect survival and distribution. In this study, we characterized the gene expression profiles of red (PAR) and green (PAG) morphs of the pea aphid (Acyrthosiphon pisum) at three high temperatures (30 °C, 36 °C, and 38 °C) and three treatment durations (6 h, 12 h, and 24 h) by high-throughput sequencing. Both PARs and PAGs increased the number of significantly differentially expressed genes as temperature and treatment duration increased, particularly for genes associated with stress resistance, lipid metabolism, cuticular protein expression, and the initiation of various regulatory mechanisms. However, the response mechanisms and their intensities varied between the morphs. More cuticular protein genes were down-regulated in PAGs, while more stress resistance genes up-regulated in PARs. JAK-STAT, MAPK, Estrogen, Insulin signaling, and Longevity-regulating pathways were enriched in PARs, whereas AMPK, Insulin signaling, and Circadian rhythm pathways were enriched in PAGs. These results suggested that PARs possesses greater adaptability than PAGs under extreme high temperatures. The different temperature adaptability between morphs may represent an ecological strategy developed by A. pisum to adapt to global warming. This research enhances our understanding of the mechanisms underlying insect survival in high-temperatures environments and provides guidance for the development of control strategies.

Trehalose metabolism mediates trade-offs between reproduction and survival in beet webworm, Loxostege sticticalis, under heat stress

BACKGROUND

Temperature is an important determinant of developmental and reproductive rates in insects. Here, we investigated the physiological responses of adult beet webworm, Loxostege sticticalis L. (Lepidoptera: Crambidae), to three temperatures (16, 23 and 30 °C) focusing on trehalose metabolism.

RESULTS

Exposure of moths to 30 °C accelerated eclosion and ovarian development, but shortened the oviposition period and adult longevity, whereas exposure to 16 °C had opposite effects. Transcriptome analysis revealed that vitellogenin (VG) and vitellogenin receptor (VR) genes were up-regulated at 30 °C, as were numerous genes related to energy metabolism, including those involved in the insulin signaling pathway, the tricarboxylic acid (TCA) cycle, and glycolysis. Expression of the trehalose transporter gene TRET1 was also induced at high temperature, primarily in the ovaries, where trehalose content increased, accompanied by lipid degradation in the fat body. Treatment with the trehalase inhibitor validamycin A reduced female fecundity and longevity at 23 °C, but enhanced the expression of genes related to stress resistance and reproduction, mimicking the effect of high temperature.

CONCLUSION

Besides their practical utility for predicting the oviposition behavior and geographic distribution of L. sticticalis in the field, these results elucidate the various physiological roles of trehalose in L. sticticalis during exposure of moths to high temperature and may provide insights into the relationship between stress resistance and reproduction in insects more generally. © 2024 Society of Chemical Industry.

Navigating Climate Change: Exploring the Dynamics Between Plant-Soil Microbiomes and Their Impact on Plant Growth and Productivity

Understanding the intricate interplay between plant and soil microbiomes and their effects on plant growth and productivity is vital in a rapidly changing climate. This review explores the interconnected impacts of climate change on plant-soil microbiomes and their profound effects on agricultural productivity. The ongoing rise in global temperatures, shifting precipitation patterns and extreme weather events significantly affect the composition and function of microbial communities in the rhizosphere. Changes in microbial diversity and activity due to rising temperatures impact nutrient cycling, microbial enzyme synthesis, soil health and pest and disease management. These changes also influence the dynamics of soil microbe communities and their capability to promote plant health. As the climate changes, plants' adaptive capacity and microbial partners become increasingly crucial for sustaining agriculture. Mitigating the adverse effects of climate change on plant growth and agricultural productivity requires a comprehensive understanding of the interconnected mechanisms driving these processes. It highlights various strategies for mitigating and adapting to environmental challenges, including soil management, stress-tolerant crops, cover cropping, sustainable land and water management, crop rotation, organic amendments and the development of climate-resilient crop varieties. It emphasises the need for further exploration of plant-soil microbiomes within the broader context of climate change. Promising mitigation strategies, including precision agriculture and targeted microbiome modifications, offer valuable pathways for future research and practical implementation of global food security and climate change.

Origins and Diversification of Myiasis Across Blowflies

Parasitism represents a prevalent and successful ecological strategy that has evolved independently numerous times across metazoa. Understanding the origin and diversification of parasitism is a central question in evolutionary biology. This study investigated the evolutionary path leading to a specific form of parasitism in blowflies known as myiasis, where larvae develop on or within a vertebrate. We modeled myiasis-associated traits, including trophic specialization (obligatory parasitism, facultative parasitism and saprophagy), larval food substrate (necrotic, fresh or both) and developmental temperature (constant, variable or both) across the blowfly phylogeny. Our results suggested that the ancestral state of blowflies likely encompassed saprophagy or facultative parasitism, with larvae developing in corpses or necrotic tissues from wounds in either homeothermic or heterothermic hosts. Furthermore, our analysis highlights the role of facultative parasitism as an intermediate step for obligate parasitism in blowflies, indicating that pre-adaptations for a facultative parasitic lifestyle may serve as stepping stones for emerging obligate parasitism. These findings shed light on the complex evolutionary history of blowfly vertebrate parasitism, emphasizing the importance of facultative parasitism as a critical transitional stage in this evolutionary process.

Thermal physiology of dung beetles exposed to ivermectin, a veterinary drug

Global changes, including increasing temperatures and pesticide contamination threaten insect survival and reproduction by altering metabolism and stress responses. Of particular importance are insects that provide ecosystem services and are threatened by multiple stressors, such as dung beetles, which bury dung in forests and cattle pastures. This study investigated how elevated temperature and ivermectin, a common antiparasitic medication used in cattle that is excreted in dung, affect the thermal physiology of Euoniticellus intermedius dung beetles under controlled laboratory conditions. Our study evaluated, under laboratory conditions, the effect of the combination of high temperature and ivermectin, on heat tolerance, metabolic rate, and survival of female dung beetles E. intermedius. We found that ivermectin reduced survival at 29 °C but not at 33 °C, potentially due to heat-induced hormetic effects, which activate defense systems, protecting organisms from the effects of a second stressor, in this case, ivermectin. Ivermectin and high temperature increased metabolic rate, which could have potential negative effects on oxidative stress and longevity. Finally, critical thermal maximum was not affected by ivermectin or temperature. By impacting physiological traits and individual survival, high temperatures and pesticides may disrupt population dynamics and ecosystem services provided by dung beetles.

The Benefit of Evolution of Pesticide Tolerance Is Overruled under Combined Stressor Exposure due to Synergistic Stressor Interactions

Despite pleas to consider both evolutionary and multistressor climate change perspectives to improve ecological risk assessment, the much needed combination of both perspectives is largely missing. This is especially important when evaluating the costs of the evolution of genetic tolerance to pollutants as these costs may become visible only under combined exposure to the pollutant and warming due to energetic constraints. We investigated the costs of chlorpyrifos tolerance in Daphnia magna when sequentially exposed to 4-day pesticide treatments and 4-day heat spike treatments. Exposure to chlorpyrifos reduced the fitness of chlorpyrifos-sensitive clones (reduced survival, mass, and reproductive performance), while it had positive (hormetic) effects on clones selected for chlorpyrifos tolerance. We did not find any costs of chlorpyrifos tolerance in the absence of the stressors and only a weak sublethal cost when only exposed to the heat spike. Notably, when sequentially exposed to the pesticide and the heat spike, the benefit of the evolution of chlorpyrifos tolerance was nullified as the chlorpyrifos-tolerant clones experienced (stronger) synergistic interactions between both stressors and stronger thermal costs when preceded by exposure to the pesticide. This highlights the importance of multistressor studies to correctly assess the costs of genetic pesticide tolerance and the potential of evolution of pesticide tolerance to rescue nontarget populations.

Climate drives the long-term ant male production in a tropical community

Forecasting insect responses to environmental variables at local and global spatial scales remains a crucial task in Ecology. However, predicting future responses requires long-term datasets, which are rarely available for insects, especially in the tropics. From 2002 to 2017, we recorded male ant incidence of 155 ant species at ten malaise traps on the 50-ha ForestGEO plot in Barro Colorado Island. In this Panamanian tropical rainforest, traps were deployed for two weeks during the wet and dry seasons. Short-term changes in the timing of male flying activity were pronounced, and compositionally distinct assemblages flew during the wet and dry seasons. Notably, the composition of these distinct flying assemblages oscillated in consistent 4-year cycles but did not change during the 16-year study period. Across time, a Seasonal Auto-Regressive Integrated Moving Average model explained 75% of long-term variability in male ant production (i.e., the summed incidence of male species across traps), which responded negatively to monthly maximum temperature, and positively to sea surface temperature, a surrogate for El Niño Southern Oscillation (ENSO) events. Establishing these relationships allowed us to forecast ant production until 2022 when year-long local climate variables were available. Consistent with the data, the forecast indicated no significant changes in long-term temporal trends of male ant production. However, simulations of different scenarios of climate variables found that strong ENSO events and maximum temperature impacted male ant production positively and negatively, respectively. Our results highlight the dependence of ant male production on both short- and long-term temperature changes, which is critical under current global warming.

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.

Assembly Graph as the Rosetta Stone of Ecological Assembly

Ecological assembly-the process of ecological community formation through species introductions-has recently seen exciting theoretical advancements across dynamical, informational, and probabilistic approaches. However, these theories often remain inaccessible to non-theoreticians, and they lack a unifying lens. Here, I introduce the assembly graph as an integrative tool to connect these emerging theories. The assembly graph visually represents assembly dynamics, where nodes symbolise species combinations and edges represent transitions driven by species introductions. Through the lens of assembly graphs, I review how ecological processes reduce uncertainty in random species arrivals (informational approach), identify graphical properties that guarantee species coexistence and examine how the class of dynamical models constrain the topology of assembly graphs (dynamical approach), and quantify transition probabilities with incomplete information (probabilistic approach). To facilitate empirical testing, I also review methods to decompose complex assembly graphs into smaller, measurable components, as well as computational tools for deriving empirical assembly graphs. In sum, this math-light review of theoretical progress aims to catalyse empirical research towards a predictive understanding of ecological assembly.

Heat domes increase vulnerability of native stingless bees by simultaneously weakening key survival traits

Heatwave events increase in frequency and duration, yet there is a strong gap in assessing their nonlethal effects on tropical insects, including beneficial social species. The stingless bees are a highly diverse group of pantropical pollinators that provide key ecosystem services. Here, we simultaneously analyzed for the first time the effect of sublethal heat stress (HS) during immature (pupal) development on adult morphology (size, shape, symmetry) and immune response of the three castes/sexes in stingless bee colonies: workers, unmated queens (gynes) and males, as well as its impact on the onset of foraging and lifespan in workers. Individuals experimentally heat stressed during development had smaller body size and reduced symmetry as adults compared with control, non-heat stressed (NHS) individuals, though the strength of the effects of HS also varied between castes and sexes. Notably, males were more prone to the effects of HS compared with workers, and less so gynes; HS reduced the immune response of males, though not that of workers or queens. Workers had significantly earlier onset of foraging and a shorter lifespan when exposed as immatures to HS. Under a worst-case scenario, knock-on negative impacts on individual survival caused by HS could compromise colony fitness. In the long-term, heatwaves may also have repercussions for the persistence of stingless bee species, the sustainability of key ancestral activities like meliponiculture and ecosystem services. Measures to ameliorate the effect of climatic warming are urgently needed to protect these pollinators, which represent an iconic world heritage.

Effects of temperature on the development of Rachiplusia nu (Lepidoptera: Noctuidae) and Chrysodeixis includens (Lepidoptera: Noctuidae) and implications on population growth in Brazil

Temperature is an elementary component in mathematical models for predicting the biotic potential of insects. In this study, the objective was to evaluate the impact of different constant temperatures of 8, 10, 15, 20, 25, 30, and 32°C on the biological parameters, lower temperature thresholds (TT), and estimating the number of annual generations (NAG) of Rachiplusia nu and Chrysodeixis includens, both pests associated with the soybean crop in Brazil. There was no development of the immature stages of R. nu at 8°C, as was also found for C. includens at 8 and 10°C. However, at 10°C all stages of R. nu developed. In general, temperatures of 20 and 25°C were the most suitable for the development of R. nu and C. includens, providing egg to adult viability of over 60% and the highest total fecundities. However, the temperature of 32°C negatively affected the parameters of the fertility life table. Rachiplusia nu showed the lowest TT (eggs: 4.9°C; larvae: 10.8°C; pupa: 14.1°C; and egg to adult: 8.9°C) when compared with C. includens (eggs: 7.5°C; larvae: 15.3°C; pupa: 16.1°C; and egg to adult: 11.3°C). Based on TT values, the NAG varied from 3.9 in cold regions to 7.5 in warm regions. However, for C. includens, we can infer that the species can reach up to 8.8 generations in warm regions. The results of the present study are important for understanding the occurrence of R. nu and C. includens in field conditions and can help with the implications of management strategies.

New Behavior Records of the Oxysternon palemo Castelnau, 1840 (Coleoptera: Scarabaeidae: Scarabaeinae) in Cerrado

The present study reports new behavioral records for Oxysternon palemo Castelnau, 1840 in Cerrado. According to its nesting habits and resource allocation, this species of dung beetle is traditionally classified as coprophagous and paracoprid, transporting portions of dung through tunnels excavated below the resource. We observed a male individual moving a pequi seed (Caryocar brasiliensis Cambess.) with "head-butting," acting as a secondary seed disperser. At another moment, we recorded necrophagous habits for the species when male individuals were observed moving pieces of domestic pig carcasses (Sus scrofa L., 1758), also with "head-butting." After, we recorded a female O. palemo, accompanied by a male individual, butting a dung mass and burying this resource several meters away from the original source. The behavior of pushing the resource over long distances is typical of telecoprid dung beetles that form dung balls and roll them using hind legs away from the resource source, unlike what is expected for O. palemo. Our hypothesis is that the observed behaviors have developed from competition for resources. Furthermore, the behaviors exhibited by O. palemo contribute to the provision of essential ecosystem services. The ecosystem services include the removal and degradation of decomposing organic matter, as well as secondary dispersal of seeds, thus supporting the maintenance and conservation of plant species.

Knockdown of the ZcVgR Gene Alters the Expression of Genes Related to Reproduction and Lifespan in Zeugodacus cucurbitae (Coquillett) Under Extreme Heat Conditions

Zeugodacus cucurbitae (Coquillett) is an important migratory vegetable pest. Previous research has demonstrated that short-term high temperatures induce differential expression of the vitellogenin receptor (ZcVgR) gene, reducing the number of eggs laid and the lifespan of female Z. cucurbitae. In this paper, we used Tandem Mass Tags (TMT) quantitative proteomics and Illumina high-throughput sequencing to determine the proteomic and transcriptomic information of female Z. cucurbitae after siRNA-mediated silencing of the target gene (ZcVgR) to gain a comprehensive understanding of the molecular mechanism of this gene in the regulation of reproduction and lifespan. The findings demonstrated that following the target gene's silencing, the ZcVgR gene's transcriptional expression was significantly downregulated, and there was no significant difference in protein level. The transcriptome and proteome had a low correlation; when the ZcVgR gene was silenced, vitellogenin-1 (ZcVg1), juvenile hormone epoxide hydrolase (JHEH), troponin C (TnC), heat shock protein 70 (HSP70), and other related genes were downregulated at the transcriptional level. By silencing the ZcVgR gene, transcriptionally level immune-related pathways were activated and energy metabolism-related pathways were inhibited; protein-level glycometabolism and phagosome pathways were activated, while phototransduction-fly and autophagy-animal pathways were inhibited. The findings of this study might offer a theoretical foundation for integrated management of Z. cucurbitae in the summertime.

Dark diversity of Odonata in Amazonian streams

The biological diversity of a region may not be fully sampled due to the low abundance or rarity of species, or the absence of species determined by their niche specificity. Investigating these species is essential for understanding the unrealized ecological potential in different habitats, identifying gaps in local and regional communities, and gaining a better understanding of the impacts of environmental changes. Therefore, to expand knowledge about the diversity of Odonata in Eastern Amazonia considering the absent species, we tested the hypotheses that: 1) Environmental variables will influence dark diversity, with greater explanation by canopy cover where sites with lower canopy cover will have higher dark diversity values, and; 2) Functional traits associated with better species dispersal will be correlated with low dark diversity of Odonata, such as larger and wider wings for example. For this, adult Odonata specimens were sampled, while structural habitat characteristics and physical and chemical water variables were measured in 128 first- to third-order streams in the Eastern Amazon. Morphological and behavioral data were recorded for each specimen. Generalized linear models were applied to predict the effects of habitat structural characteristics and physical and chemical water variables on the dark diversity of Odonata. Additionally, we assessed which functional traits contribute most to the variation of dark diversity within these communities. Habitat structural features and physical and chemical water variables had no effect on dark diversity. Morphological traits, such as body conformation, with species having narrower wings, longer hind wings, narrower thoraxes, and shorter abdomens, comprised most of the dark diversity. The dispersal limitations of some Odonata species strongly suggest the role of space and time in nature planning and management.

Senescence of humoral antimicrobial immunity occurs in infected mosquitoes when the temperature is higher

Mosquitoes cannot use metabolism to regulate their body temperature and therefore climate warming is altering their physiology. Mosquitoes also experience a physiological decline with aging, a phenomenon called senescence. Because both high temperature and aging are detrimental to mosquitoes, we hypothesized that high temperatures accelerate senescence. Here, we investigated how temperature and aging, independently and interactively, shape the antimicrobial immune response of the mosquito Anopheles gambiae. Using a zone-of-inhibition assay that measures the antimicrobial activity of hemolymph, we found that antimicrobial activity increases following infection. Moreover, in infected mosquitoes, antimicrobial activity weakens as the temperature rises to 32°C, and antimicrobial activity increases from 1 to 5 days of age and stabilizes with further aging. Importantly, in E. coli-infected mosquitoes, higher temperature causes an aging-dependent decline in antimicrobial activity. Altogether, this study demonstrates that higher temperature can accelerate immune senescence in infected mosquitoes, thereby interactively shaping their ability to fight an infection.

Resilience mechanisms of Trichopria drosophilae (Hymenoptera: Diapriinae) under global extreme cooling: insights into parasitic response and physiological adaptation

Global climate warming and frequent extreme low-temperature events have made it essential to investigate the impact of low temperatures on parasitic wasps to protect and strengthen farmland biodiversity, which in turn enhances the biological control potential of natural enemies such as parasitic wasps. We systematically examined how low-temperature stress affects the parasitic functional response of Trichopria drosophilae to Drosophila suzukii (Diptera: Drosophilidae) pupae. Our findings indicate that the parasitic behavior of T. drosophilae towards D. suzukii pupae aligns with the Holling II functional response model following exposure to different temperatures. Within the temperature range of 8 °C to -8 °C, lower temperatures correlated decreased instantaneous attack rate of T. drosophilae and an increase in processing time. The search constant Q initially increased and then decreased with declining temperatures. Short-term low-temperature stress negatively impacted the parasitic and searching abilities of T. drosophilae but did not alter its parasitic functional response model. Notably, short-term low-temperature stress had minimal effects on the water content, protein content, and total sugar content of male and female T. drosophilae adults. However, as temperatures decreased, the activities of key enzymes, including GAPDH, SOD, T-AOC, and malondialdehyde (MDA), exhibited an initial increase followed by a decrease. Conversely, the activities of LDH and HOAD decreased, while the activities of CAT and POD increased. Further study on the effect of short-term low temperature on T. drosophilae can provide a research basis for the large-scale production and low-temperature refrigeration technology of T. drosophilae, and provide a scientific basis for its efficient use in the field.

Evaluating the effects of short-term low temperature on the growth and development of Trichopria drosophilae based on the age-stage two-sex life table

BACKGROUND

The effects of low temperatures on parasitic wasps are crucial for maintaining farmland biodiversity and enhancing biological control, especially given the implications of global warming and frequent extreme cold events.

METHODS

We studied the effects of different low temperatures (-8 ± 1 °C, -4 ± 1 °C, 0 ± 1 °C, 4 ± 1 °C, and 8 ± 1 °C) on the mating frequency and duration of male adults of Trichopria drosophilae and the number of pupae beaten by female adults, and constructed the age-stage two-sex life table of T. drosophilae.

RESULTS

This study found that male T. drosophilae adults exposed to low temperatures for 12 h significantly altered their mating behavior, peaking between 15:00 and 17:00. As the temperature dropped during the exposure, both the mating frequency of T. drosophilae and the duration of pupal beating were affected. The survival rate of female adults dropped from 39.55% at 8 °C to just 21.17% at -8 °C. Low-temperature treatment shortened the development period and lifespan for T. drosophilae adults. They developed 4.71 days faster and had a total lifespan that was 10.66 days shorter than those in the control group after being exposed to -8 °C. Furthermore, the average number of eggs laid by females at -8 °C was 4.46 less than that at 8 °C and 6.16 less than that in the control group, which laid an average of 21.55 eggs. The net reproductive rate (R0) of T. drosophilae decreased with lower temperatures, reaching a low of 23.64 at -8 °C. Conversely, the intrinsic growth rate (rm) actually increased as temperatures dropped, with the lowest value being 0.21 at -8 °C.

CONCLUSIONS

The findings indicate that short-term exposure to low temperatures hampers the growth and population increase of T. drosophilae, thereby reducing their effectiveness as biological control agents.

Fertility loss and recovery dynamics after repeated heat stress across life stages in male Drosophila melanogaster: patterns and processes

Frequent and extreme temperatures associated with climate change pose a major threat to biodiversity, particularly for organisms whose metabolism is strictly linked to ambient temperatures. Many studies have explored thermal effects on survival, but heat-induced fertility loss is emerging as a greater threat to population persistence. However, while evidence is accumulating that both juvenile and adult stages heat exposure can impair fertility in their own ways, much less is known about the immediate and longer-term fitness consequences of repeated heat stress across life stages. To address this knowledge gap, we used male Drosophila melanogaster to investigate (i) the cumulative fitness effects of repeated heat stress across life stages, (ii) the potential of recovery from these heat exposures, and (iii) the underlying mechanisms. We found individual and combined effects of chronic juvenile and acute adult heat stress on male fitness traits. These effects tended to exacerbate over several days after brief heat exposure, indicating a substantial fertility loss for these short-lived organisms. Our findings highlight the cumulative and persistent effects of heat stress on fitness. Such combined effects could accelerate population declines, particularly in more vulnerable species, emphasizing the importance of considering reproduction and its recovery for more accurate models of species persistence.

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.

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.

A potential trade-off between reproduction and enhancement of thermotolerance in Liriomyza trifolii populations driven by thermal acclimation

The invasive pest, Liriomyza trifolii, poses a significant threat to ornamental and vegetable plants. It spreads rapidly and causes large-scale outbreaks with pronounced thermotolerance. In this study, we developed L. trifolii strains adapted to high temperatures (strains designated 35 and 40); these were generated from a susceptible strain (designated S) by long-term thermal acclimation to 35 °C and 40 °C, respectively. Age-stage, two-sex life tables, thermal preferences, critical thermal limits, knockdown behaviors, eclosion and survival rates as well as expression of genes encoding heat shock proteins (Hsps) were compared for the three strains. Our findings indicated that the thermotolerance of L. trifolii was enhanced after long-term thermal acclimation, which suggested an adaptive plastic response to thermal stress. A trade-off between reproduction and thermotolerance was observed under thermal stress, potentially improving survival of the population and fostering adaptionary changes. Acclimation at 35 °C improved reproductive performance and population density of L. trifolii, particularly by enhancing the fecundity of female adults and accelerating the speed of development. Although the 40 strain exhibited the highest developmental speed and greater thermotolerance, it incurred a larger reproductive cost. This study provides a theoretical framework for monitoring and controlling leafminers and understanding their evolutionary adaptation to environmental changes.

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.

Temperature-mediated dynamics: Unravelling the impact of temperature on cuticular hydrocarbon profiles, mating behaviour, and life history traits in three Drosophila species

In a world grappling with climate change, understanding the enduring impact of changes in temperatures on insect adult traits is crucial. It is proposed that cold- and warm-adapted species exhibit specialized behavioural and physiological responses to their respective temperature ranges. In contrast, generalist species maintain more stable metabolic and developmental rates across a broader range of temperatures, reflecting their ability to exploit diverse thermal niches. Here, we explored this intricate response to temperature exposure in three Drosophila species: Drosophila ezoana originating in Arctic regions, D. novamexicana in arid, hot environments, and in the cosmopolitan species D. virilis. Rearing these flies at 15, 20, 25, and 30 °C revealed striking variations in their cuticular hydrocarbon (CHC) profiles, known to mediate mate recognition and prevent water loss in insects. The cold-adapted D. ezoana consistently exhibited reduced CHC levels with increasing temperatures, while the warm-adapted D. novamexicana and the cosmopolitan D. virilis displayed more nuanced responses. Additionally, we observed a significant influence of rearing temperature on the mating behaviour of these flies, where those reared at the extreme temperatures, 15 and 30 °C, exhibiting reduced mating success. Consequently, this led to a decrease in the production of adult offspring. Also, these adult offspring underwent notable alterations in life history traits, reaching adulthood more rapidly at 25 and 30 °C but with lower weight and reduced longevity. Furthermore, among these offspring, those produced by the cold-adapted D. ezoana were more vulnerable to desiccation and starvation than those from the warm-adapted D. novamexicana and the cosmopolitan D. virilis. In summary, our research demonstrates that Drosophila species from diverse ecological regions exhibit distinct responses to temperature changes, as evidenced by variations in CHC profiles, mating behaviours, fertility, and life history traits. This provides valuable insights into how environmental conditions shape the biology and ecology of insects.

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.

Warmer environmental temperature accelerates aging in mosquitoes, decreasing longevity and worsening infection outcomes

BACKGROUND

Most insects are poikilotherms and ectotherms, so their body temperature is predicated by environmental temperature. With climate change, insect body temperature is rising, which affects how insects develop, survive, and respond to infection. Aging also affects insect physiology by deteriorating body condition and weakening immune proficiency via senescence. Aging is usually considered in terms of time, or chronological age, but it can also be conceptualized in terms of body function, or physiological age. We hypothesized that warmer temperature decouples chronological and physiological age in insects by accelerating senescence. To investigate this, we reared the African malaria mosquito, Anopheles gambiae, at 27 °C, 30 °C and 32 °C, and measured survival starting at 1-, 5-, 10- and 15-days of adulthood after no manipulation, injury, or a hemocoelic infection with Escherichia coli or Micrococcus luteus. Then, we measured the intensity of an E. coli infection to determine how the interaction between environmental temperature and aging shapes a mosquito's response to infection.

RESULTS

We demonstrate that longevity declines when a mosquito is infected with bacteria, mosquitoes have shorter lifespans when the temperature is warmer, older mosquitoes are more likely to die, and warmer temperature marginally accelerates the aging-dependent decline in survival. Furthermore, we discovered that E. coli infection intensity increases when the temperature is warmer and with aging, and that warmer temperature accelerates the aging-dependent increase in infection intensity. Finally, we uncovered that warmer temperature affects both bacterial and mosquito physiology.

CONCLUSIONS

Warmer environmental temperature accelerates aging in mosquitoes, negatively affecting both longevity and infection outcomes. These findings have implications for how insects will serve as pollinators, agricultural pests, and disease vectors in our warming world.

Heat Shock Protein 70 Genes Are Involved in the Thermal Tolerance of Hippodamia variegata

Previous studies have shown that the survival and reproduction of Hippodamia variegata are increasingly harmed by progressive increases in temperature (from 32 °C to 35 °C and 38 °C). In this study, transcriptome sequencing analysis was performed on H. variegata, after being exposed to different temperatures (from 32 to 38 °C) for 24 h, using high-throughput sequencing technology. We found the largest number of differentially expressed genes (DEGs) in the 35 °C vs. 32 °C group (1151) followed by the 38 °C vs. 32 °C group (1054) and then the 38 °C vs. 35 °C group (901), indicating that H. variegata expressed the largest number of newly mobilized genes under medium-high temperature (35 °C). Gene functional analysis showed that a large number of DEGs were involved in "Catalytic activity", "Oxidoreductase activity", "Metabolic pathways", and "Longevity regulating pathway-multiple species" gene groups. We randomly selected nine DEGs for validation using qRT-PCR. The results of qRT-PCR were consistent with the transcriptome data, confirming their reliability. Finally, the RNAi results showed that adult survival, longevity, and fecundity were lower in the group in which gene expression of the heat shock proteins (Hsp70-01 and Hsp68) was suppressed than in the control group (injection ds-GFP) at all the experimental temperatures (32, 35, and 38 °C). Our results indicate the important role of the heat shock proteins (Hsp70-01 and Hsp68) in resistance to high-temperature stress in H. variegata and provide a molecular basis for analyzing its thermotolerance mechanism.

Evolutionary adaptation under climate change: Aedes sp. demonstrates potential to adapt to warming

Climate warming is expected to shift the distributions of mosquitoes and mosquito-borne diseases, facilitating expansions at cool range edges and contractions at warm range edges. However, whether mosquito populations could maintain their warm edges through evolutionary adaptation remains unknown. Here, we investigate the potential for thermal adaptation in Aedes sierrensis, a congener of the major disease vector species that experiences large thermal gradients in its native range, by assaying tolerance to prolonged and acute heat exposure, and its genetic basis in a diverse, field-derived population. We found pervasive evidence of heritable genetic variation in acute heat tolerance, which phenotypically trades off with tolerance to prolonged heat exposure. A simple evolutionary model based on our data shows that the estimated maximum rate of evolutionary adaptation in mosquito heat tolerance typically exceeds that of projected climate warming under idealized conditions. Our findings indicate that natural mosquito populations may have the potential to track projected warming via genetic adaptation. Prior climate-based projections may thus underestimate the range of mosquito and mosquito-borne disease distributions under future climate conditions.

Heat stress-induced oviposition behavioral change correlates with sperm damage in the pine sawyer beetle, Monochamus alternatus

BACKGROUND

Global climate change is causing an increase in extreme high temperatures (EHTs), which subject insects to unprecedented stress. Behavior plasticity in response to EHTs, particularly oviposition behavior, is important for the persistence and outbreak of insect populations. Investigating the plasticity of oviposition behavior and its underlying mechanisms has theoretical importance to pest management, but knowledge gaps still remain.

RESULTS

Herein, we characterized the reproductive traits of Monochamus alternatus, a dominant insect vector of the destructive pine wilt disease, including oviposition behavioral patterns, fecundity, offspring fitness and sperm viability, under simulated heatwave conditions in the laboratory. The results showed that (i) EHTs induced a novel oviposition behavior, whereby females deposited multiple eggs into a single groove rather than laying one egg per groove under normal condition; (ii) EHTs exerted stage- and sex-specific effects on fecundity, offspring fitness and sperm viability; and (iii) there was a significant correlation between frequency of the novel oviposition strategy and sperm viability.

CONCLUSION

We hypothesized that this beetle pest has the ability to flexibly shift towards a low-cost oviposition strategy to counteract the fitness costs caused by heat stress. Taken together, these findings provide a theoretical foundation for personalized pest management strategies in the context of climate change. © 2024 Society of Chemical Industry.

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.

Effects of short-term high temperature at different life stages on reproductive fitness in Mythimna separata (Lepidoptera: Noctuidae)

Extreme heat events commonly occur under climate warming. All life stages of insects may experience the occurrence of extremely high temperatures. However, the effects of short-term extreme heat events on life-history traits remain unclear in most migratory pests. Here, we investigated the biological effects of short-term heat exposure (35 °C for 4 h) at different life stages on Mythimna separata Walker (Lepidoptera: Noctuidae), a typical migratory pest. We found that the reproductive sensitivity of pupae and adults was higher than that of 3rd-instar larvae. Increasing the frequency of heat exposure decreased the reproductive performance of M. separata at all life stages. Parental short-term heat exposures could cause transgenerational damage to offspring survival and reproductive fitness when the exposure frequency reached 3 times. Our results suggest that short-term exposure to extreme temperatures could impact reproductive fitness across different life stages in M. separata. This should be taken into consideration in the population prediction of migratory pests under climate change.