Evolutionary impacts of winter climate change on insects

A quantitative model of temperature-dependent diapause progression

Winter diapause in insects is commonly terminated through cold exposure, which, like vernalization in plants, prevents development before spring arrives. Currently, quantitative understanding of the temperature dependence of diapause termination is limited, likely because diapause phenotypes are generally cryptic to human eyes. We introduce a methodology to tackle this challenge. By consecutively moving butterfly pupae of the species Pieris napi from several different cold conditions to 20 °C, we show that diapause termination proceeds as a temperature-dependent rate process, with maximal rates at relatively cold temperatures and low rates at warm and extremely cold temperatures. Further, we show that the resulting thermal reaction norm can predict P. napi diapause termination timing under variable temperatures. Last, we show that once diapause is terminated in P. napi, subsequent development follows a typical thermal performance curve, with a maximal development rate at around 31 °C and a minimum at around 2 °C. The sequence of these thermally distinct processes (diapause termination and postdiapause development) facilitates synchronous spring eclosion in nature; cold microclimates where diapause progresses quickly do not promote fast postdiapause development, allowing individuals in warmer winter microclimates to catch up, and vice versa. The unveiling of diapause termination as one temperature-dependent rate process among others promotes a parsimonious, quantitative, and predictive model, wherein winter diapause functions both as an adaptation against premature development during fall and winter and for synchrony in spring.

Structural and functional analysis of aquaporins in Bombus terrestris

Bombus terrestris are efficient pollinators in forestry and agriculture, with higher cold tolerance than other bees. Yet, their cold tolerance mechanism remains unclear. Aquaporins (AQPs) function as cell membrane proteins facilitating rapid water flow, aiding in osmoregulation. Recent studies highlight the importance of insect AQPs in dehydration and cold stress. Comparative transcriptome analysis of B. terrestris under cold stress revealed up-regulation of four AQPs, indicating their potential role in cold tolerance. Seven AQPs-Eglp1, Eglp2, Eglp3, DRIP, PRIP, Bib, and AQP12L-have been identified in B. terrestris. These are widely expressed in various tissues, particularly in the alimentary canal and Malpighian tubules. Functional analysis of BterAQPs in the Xenopus laevis oocytes expressing system showed distinct water and glycerol selectivity, with BterDrip exhibiting the highest water permeability. Molecular modeling of BterDrip revealed six transmembrane domains, two NPA motifs, and an ar/R constriction region (Phe131, His256, Ser265, and Arg271), likely contributing to its water selectivity. Silencing BterDRIP accelerated mortality in B. terrestris under cold stress, highlighting the crucial role of BterDRIP in their cold tolerance and providing a molecular mechanism for their cold adaptation.

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.

Physiological responses to a changing winter climate in an early spring-breeding amphibian

Climate change is swiftly altering environmental winter conditions, leading to significant ecological impacts such as phenological shifts in many species. As a result, animals might face physiological mismatches due to longer or earlier activity periods and are at risk of being exposed to late spring freezes. Our study points for the first time to the complex physiological challenges that amphibians face as a result of changing thermal conditions due to winter climate change. We investigated the physiological responses to a period of warmer winter days and sudden spring freeze in the common toad (Bufo bufo) by acclimating them to 4°C or 8°C for 48 h or exposing them to 4°C or -2°C for 6 h, respectively. We assessed the daily energy demands, determined body condition and cold tolerance, explored the molecular responses to freezing through hepatic tissue transcriptome analysis, and measured blood glucose levels. Toads acclimated to higher temperatures showed a higher daily energy expenditure and a reduced cold tolerance suggesting faster depletion of energy stores and the loss of winter acclimation during warmer winters. Blood sugar levels were higher in frozen toads indicating the mobilization of cryoprotective glucose with freezing which was further supported by changed patterns in proteins related to glucose metabolism. Overall, our results emphasize that increased thermal variability incurs physiological costs that may reduce energy reserves and thus affect amphibian health and survival. This might pose a serious threat to breeding adults and may have subsequent effects at the population level.

Variation in Thermal Sensitivity of Diapause Development among Individuals and over Time Predicts Life History Timing in a Univoltine Insect

AbstractPhysiological time is important for understanding the development and seasonal timing of ectothermic animals but has largely been applied to developmental processes that occur during spring and summer, such as morphogenesis. There is a substantial knowledge gap in the relationship between temperature and development during winter, a season that is increasingly impacted by climate change. Most temperate insects overwinter in diapause, a developmental process with little obvious morphological change. We used principles from the physiological time literature to measure and model the thermal sensitivity of diapause development rate in the apple maggot fly Rhagoletis pomonella, a univoltine fly whose diapause duration varies substantially within and among populations. We show that diapause duration can be predicted by modeling a relationship between temperature and development rate that is shifted toward lower temperatures compared with typical models of morphogenic, nondiapause development. However, incorporating interindividual variation and ontogenetic variation in the temperature-to-development rate relationship was critical for accurately predicting fly emergence, as diapause development proceeded more quickly at high temperatures later in diapause. We conclude that the conceptual framework may be flexibly applied to other insects and discuss possible mechanisms of diapause timers and implications for phenology with warming winters.

The freeze-avoiding mountain pine beetle (Dendroctonus ponderosae) survives prolonged exposure to stressful cold by mitigating ionoregulatory collapse

Insect performance is linked to environmental temperature, and surviving through winter represents a key challenge for temperate, alpine and polar species. To overwinter, insects have adapted a range of strategies to become truly cold hardy. However, although the mechanisms underlying the ability to avoid or tolerate freezing have been well studied, little attention has been given to the challenge of maintaining ion homeostasis at frigid temperatures in these species, despite this limiting cold tolerance for insects susceptible to mild chilling. Here, we investigated how prolonged exposure to temperatures just above the supercooling point affects ion balance in freeze-avoidant mountain pine beetle (Dendroctonus ponderosae) larvae in autumn, mid-winter and spring, and related it to organismal recovery times and survival. Hemolymph ion balance was gradually disrupted during the first day of exposure, characterized by hyperkalemia and hyponatremia, after which a plateau was reached and maintained for the rest of the 7-day experiment. The degree of ionoregulatory collapse correlated strongly with recovery times, which followed a similar asymptotical progression. Mortality increased slightly during extensive cold exposures, where hemolymph K+ concentration was highest, and a sigmoidal relationship was found between survival and hyperkalemia. Thus, the cold tolerance of the freeze-avoiding larvae of D. ponderosae appears limited by the ability to prevent ionoregulatory collapse in a manner similar to that of chill-susceptible insects, albeit at much lower temperatures. Based on these results, we propose that a prerequisite for the evolution of insect freeze avoidance may be a convergent or ancestral ability to maintain ion homeostasis during extreme cold stress.

Geographic variation in larval cold tolerance and exposure across the invasion front of a widely established forest insect

Under global climate change, high and low temperature extremes can drive shifts in species distributions. Across the range of a species, thermal tolerance is based on acclimatization, plasticity, and may undergo selection, shaping resilience to temperature stress. In this study, we measured variation in cold temperature tolerance of early instar larvae of an invasive forest insect, Lymantria dispar dispar L. (Lepidoptera: Erebidae), using populations sourced from a range of climates within the current introduced range in the Eastern United States. We tested for population differences in chill coma recovery (CCR) by measuring recovery time following a period of exposure to a nonlethal cold temperature in 2 cold exposure experiments. A 3rd experiment quantified growth responses after CCR to evaluate sublethal effects. Our results indicate that cold tolerance is linked to regional climate, with individuals from populations sourced from colder climates recovering faster from chill coma. While this geographic gradient is seen in many species, detecting this pattern is notable for an introduced species founded from a single point-source introduction. We demonstrate that the cold temperatures used in our experiments occur in nature during cold spells after spring egg hatch, but impacts to growth and survival appear low. We expect that population differences in cold temperature performance manifest more from differences in temperature-dependent growth than acute exposure. Evaluating intraspecific variation in cold tolerance increases our understanding of the role of climatic gradients on the physiology of an invasive species, and contributes to tools for predicting further expansion.

Rapid and Repeated Climate Adaptation Involving Chromosome Inversions following Invasion of an Insect

Following invasion, insects can become adapted to conditions experienced in their invasive range, but there are few studies on the speed of adaptation and its genomic basis. Here, we examine a small insect pest, Thrips palmi, following its contemporary range expansion across a sharp climate gradient from the subtropics to temperate areas. We first found a geographically associated population genetic structure and inferred a stepping-stone dispersal pattern in this pest from the open fields of southern China to greenhouse environments of northern regions, with limited gene flow after colonization. In common garden experiments, both the field and greenhouse groups exhibited clinal patterns in thermal tolerance as measured by critical thermal maximum (CTmax) closely linked with latitude and temperature variables. A selection experiment reinforced the evolutionary potential of CTmax with an estimated h2 of 6.8% for the trait. We identified 3 inversions in the genome that were closely associated with CTmax, accounting for 49.9%, 19.6%, and 8.6% of the variance in CTmax among populations. Other genomic variations in CTmax outside the inversion region were specific to certain populations but functionally conserved. These findings highlight rapid adaptation to CTmax in both open field and greenhouse populations and reiterate the importance of inversions behaving as large-effect alleles in climate adaptation.

Diapause survival requires a temperature-sensitive preparatory period

Diapause is a form of internally-controlled dormancy that allows insects to avoid stressful conditions and periods of low food availability. Eastern spruce budworm (Choristoneura fumiferana Clemens), like many cold-adapted insects, enter diapause well in advance of winter conditions, thus exposing them to elevated temperatures during fall that can deplete energy stores and impact post-diapause survival. We explored the impact of fall conditions on C. fumiferana by manipulating the length of the fall period and exposure temperatures during the diapause initiation phase of second instar larvae in a factorial design. We exposed second instar larvae to four fall temperatures (10, 15, 20, and 25°C) and five exposure times (1, 2, 4, 6, and 10 weeks) prior to standardized diapause conditions. We measured metabolites (glycogen, glycerol, and protein) prior to and during diapause for a subset of individuals. We also measured post-diapause survival by quantifying emergence following diapause conditions for a subset of individuals. We found that long, warm fall conditions depleted glycogen content and lowered post-diapause survival. We also found that short, cool conditions impacted post-diapause survival, although glycogen content remained high. Our results showed that fall conditions have substantial fitness consequences to overwintering insects. Optimal fall conditions struck a balance between exposure time and temperature. Our findings point to a potentially adaptive reason for early diapause onset: that an undescribed, but temperature-sensitive process is occurring in C. fumiferana larvae during the diapause initiation period that is essential for overwintering survival and successful post-diapause emergence.

Shifts in population density centers of a hibernating mammal driven by conflicting effects of climate change and disease

Populations wax and wane over time in response to an organism's interactions with abiotic and biotic forces. Numerous studies demonstrate that fluctuations in local populations can lead to shifts in relative population densities across the geographic range of a species over time. Fewer studies attempt to disentangle the causes of such shifts. Over four decades (1983-2022), we monitored populations of hibernating Indiana bats (Myotis sodalis) in two areas separated by ~110 km. The number of bats hibernating in the northern area increased from 1983 to 2011, while populations in the southern area remained relatively constant. We used simulation models and long-term weather data to demonstrate the duration of time bats must rely on stored fat during hibernation has decreased in both areas over that period, but at a faster rate in the northern area. Likewise, increasing autumn and spring temperatures shortened the periods of sporadic prey (flying insect) availability at the beginning and end of hibernation. Climate change thus increased the viability of northern hibernacula for an increasing number of bats by decreasing energetic costs of hibernation. Then in 2011, white-nose syndrome (WNS), a disease of hibernating bats that increases energetic costs of hibernation, was detected in the area. From 2011 to 2022, the population rapidly decreased in the northern area and increased in the southern area, completely reversing the northerly shift in population densities associated with climate change. Energy balance during hibernation is the singular link explaining the northerly shift under a changing climate and the southerly shift in response to a novel disease. Continued population persistence suggests that bats may mitigate many impacts of WNS by hibernating farther south, where insects are available longer each year.

Winter is coming: Interactions of multiple stressors in winter and implications for the natural world

Winter is a key driver of ecological processes in freshwater, marine and terrestrial ecosystems, particularly in higher latitudes. Species have evolved various adaptive strategies to cope with food limitations and the cold and dark wintertime. However, human-induced climate change and other anthropogenic stressors are impacting organisms in winter in unpredictable ways. In this paper, we show that global change experiments investigating multiple stressors have predominantly been conducted during summer months. However, effects of anthropogenic stressors sometimes differ between winter and other seasons, necessitating comprehensive investigations. Here, we outline a framework for understanding the different effects of anthropogenic stressors in winter compared to other seasons and discuss the primary mechanisms that will alter ecological responses of organisms (microbes, animals and plants). For instance, while the magnitude of some anthropogenic stressors can be greater in winter than in other seasons (e.g. some pollutants), others may alleviate natural winter stress (e.g. warmer temperatures). These changes can have immediate, delayed or carry-over effects on organisms during winter or later seasons. Interactions between stressors may also vary with season. We call for a renewed research direction focusing on multiple stressor effects on winter ecology and evolution to fully understand, and predict, how ecosystems will fare under changing winters. We also argue the importance of incorporating the interactions of anthropogenic stressors with winter into ecological risk assessments, management and conservation efforts.

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.

Snow flies self-amputate freezing limbs to sustain behavior at sub-zero temperatures

Temperature profoundly impacts all living creatures. In spite of the thermodynamic constraints on biology, some animals have evolved to live and move in extremely cold environments. Here, we investigate behavioral mechanisms of cold tolerance in the snow fly (Chionea spp.), a flightless crane fly that is active throughout the winter in boreal and alpine environments of the northern hemisphere. Using thermal imaging, we show that adult snow flies maintain the ability to walk down to an average body temperature of -7°C. At this supercooling limit, ice crystallization occurs within the snow fly's hemolymph and rapidly spreads throughout the body, resulting in death. However, we discovered that snow flies frequently survive freezing by rapidly amputating legs before ice crystallization can spread to their vital organs. Self-amputation of freezing limbs is a last-ditch tactic to prolong survival in frigid conditions that few animals can endure. Understanding the extreme physiology and behavior of snow insects holds particular significance at this moment when their alpine habitats are rapidly changing due to anthropogenic climate change. VIDEO ABSTRACT.

Clinal variation in the temperature and photoperiodic control of reproductive diapause in Drosophila montana females

Insect adaptation to climatic conditions at different latitudes has required changes in life-history traits linked with survival and reproduction. Several species, including Drosophila montana, show robust latitudinal variation in the critical day length (CDL), below which more than half of the emerging females enter reproductive diapause at a given temperature. Here we used a novel approach to find out whether D. montana also shows latitudinal variation in the critical temperature (CTemp), above which the photoperiodic regulation of diapause is disturbed so that the females develop ovaries in daylengths that are far below their CDL. We estimated CTemp for 53 strains from different latitudes on 3 continents after measuring their diapause proportions at a range of temperatures in 12 h daylength (for 29 of the strains also in continuous darkness). In 12 h daylength, CTemp increased towards high latitudes alongside an increase in CDL, and in 3 high-latitude strains diapause proportion exceeded 50% in all temperatures. In continuous darkness, the diapause proportion was above 50% in the lowest temperature(s) in only 9 strains, all of which came from high latitudes. In the second part of the study, we measured changes in CTemp and CDL in a selection experiment favouring reproduction in short daylength (photoperiodic selection) and by exercising selection for females that reproduce in LD12:12 at low temperature (photoperiodic and temperature selection). In both experiments selection induced parallel changes in CDL and CTemp, confirming correlations seen between these traits along latitudinal clines. Overall, our findings suggest that selection towards strong photoperiodic diapause and long CDL at high latitudes has decreased the dependency of D. montana diapause on environmental temperature. Accordingly, the prevalence and timing of the diapause of D. montana is likely to be less vulnerable to climate warming in high- than low-latitude populations.

Transcriptomic evidence indicates that montane leaf beetles prioritize digestion and reproduction in a sex-specific manner during emergence from dormancy

During winter, many organisms conserve resources by entering dormancy, suppressing metabolism and biosynthesis. The transition out of winter dormancy to summer activity requires a quick reversal of this suppression, in order to exploit now-favorable environmental conditions. To date, mechanisms by which winter climate variation affects this transition remains unelucidated. Here we experimentally manipulated snow cover for naturally overwintering montane leaf beetles (Chrysomela aeneicollis), and profiled changes in gene expression during the transition out of dormancy in spring. Upon emergence, beetles up-regulate transcripts associated with digestion and nutrient acquisition and down regulate those associated with lipid metabolism, suggesting a shift away from utilizing stored lipid and towards digestion of carbohydrate-rich host plant tissue. Development of digestive capacity is followed by up-regulation of transcripts associated with reproduction; a transition that occurs earlier in females than males. Snow manipulation strongly affected the ground thermal regime and correspondingly gene expression profiles, with beetles showing a delayed up-regulation of reproduction in the dry compared to snowy plots. This suggests that winter conditions can alter the timing and prioritization of processes during emergence from dormancy, potentially magnifying the effects of declining snow cover in the Sierra's and other snowy mountains.

Contrasting effects of an extended fall period and winter heatwaves on the overwintering fitness of diapausing disease vector, Aedes albopictus

Climate change is expected to dramatically alter autumnal and winter conditions in many temperate regions. However, limited data is available to accurately predict how these changes will impact species' overwinter survival and post-winter fitness. Here, we determine how a longer, warmer fall period and winter heatwaves affect overwintering fitness and post-winter performance of the invasive mosquito vector, Aedes albopictus. We found that a longer, warmer fall period representative of early entry into diapause did not affect overwinter survival but did lead to reduced post-winter performance for multiple traits. Specifically, larvae that experienced longer, warmer fall conditions as diapause embryos exhibited reduced post-diapause larval starvation tolerance, increased post-diapause larval mortality, and longer post-diapause larval development compared to individuals from the short-fall treatments. These negative post-diapause fitness effects likely resulted from the greater energetic demands and/or damage incurred during the warmer, longer fall period. In contrast, exposure to winter heatwaves increased overwinter survival, possibly by allowing diapausing embryos to escape or repair cold injury. Finally, fall treatment and winter heatwaves had an interactive effect on male development time, while neither treatment impacted pupal mass in either sex. Overall, our results highlight that experiments that fail to measure post-diapause fitness are likely to substantially under-estimate the impacts of climate change on post-winter performance. Additionally, our results emphasize that it is crucial to consider the potentially conflicting effects of different aspects of climate change on a species' overall overwintering success.

Soundscape phenology: The effect of environmental and climatic factors on birds and insects in a subtropical woodland

Climate change and biodiversity loss are significant global environmental issues. However, to understand their impacts we need to know how fauna respond to environmental and climatic variation over time. In this study, remote sensing techniques (satellite imagery and passive acoustic recorders) were used to investigate the variation in biophony over different timescales, ranging from one day to one year, in a sub-tropical woodland in eastern Australia. The prominent sources of biophony were birds at dawn and during the day, nocturnal insects at dusk and during the night, and diurnal birds and insects (mainly cicadas) over the summer period of December, January, and February. While different environmental factors were found to be key drivers of phenological response in different faunal groups, temperature, humidity and the interactions between temperature, humidity, moon illumination and vegetation greenness were most important factors overall. Using observed temperatures relative to the historical mean for each day of the year, we evaluated the impact of higher-than-average temperatures on calling activity. We found that nocturnal insects call less frequently on days when the temperature was hotter than average in winter months (June, July, and August), and birds call less frequently in hot spring days (September, October, and November) meaning these groups can be susceptible to temperature increase as consequence, for example, of climate change. This study demonstrates how animal calling behaviour is affected by different environmental variables over different temporal scales. This study also demonstrates the utility of remote sensing techniques for assessing the impacts of climate change on biodiversity. It is highly recommended that monitoring schemes and impact assessments account for phenological changes and environmental variability, as these are complex and important processes shaping animal communities.

Potential for urban warming to postpone overwintering dormancy of temperate mosquitoes

Cities are generally hotter than surrounding rural areas due to the Urban Heat Island (UHI) effect. These increases in temperature advance plant and animal phenology, development, and reproduction in the spring. However, research determining how increased temperatures affect the seasonal physiology of animals in the fall has been limited. The Northern house mosquito, Culex pipiens, is abundant in cities and transmits several pathogens including West Nile virus. Females of this species enter a state of developmental arrest, or reproductive diapause, in response to short days and low temperatures during autumn. Diapausing females halt reproduction and blood-feeding, and instead accumulate fat and seek sheltered overwintering sites. We found that exposure to increased temperatures in the lab that mimic the UHI effect induced ovarian development and blood-feeding, and that females exposed to these temperatures were as fecund as non-diapausing mosquitoes. We also found that females exposed to higher temperatures had lower survival rates in winter-like conditions, despite having accumulated equivalent lipid reserves relative to their diapausing congeners. These data suggest that urban warming may inhibit diapause initiation in the autumn, thereby extending the active biting season of temperate mosquitoes.

Chilled, starved or frozen: Insect mitochondrial adaptations to overcome the cold

Physiological adaptations to tackle cold exposure are crucial for insects living in temperate and arctic environments and here we review how cold adaptation is manifested in terms of mitochondrial function. Cold challenges are diverse, and different insect species have evolved metabolic and mitochondrial adaptations to: i) energize homeostatic regulation at low temperature, ii) stretch energy reserves during prolonged cold exposure, and iii) preserve structural organization of organelles following extracellular freezing. While the literature is still sparse, our review suggests that cold-adapted insects preserve ATP production at low temperatures by maintaining preferred mitochondrial substrate oxidation, which is otherwise challenged in cold-sensitive species. Chronic cold exposure and metabolic depression during dormancy is linked to reduced mitochondrial metabolism and may involve mitochondrial degradation. Finally, adaptation to extracellular freezing could be associated with superior structural integrity of the mitochondrial inner membrane following freezing which is linked to cellular and organismal survival.

Keep your cool: Overwintering physiology in response to urbanization in the acorn ant, Temnothorax curvispinosus

Winter presents a challenge for survival, yet temperate ectotherms have remarkable physiological adaptations to cope with low-temperature conditions. Under recent climate change, rather than strictly relaxing pressure on overwintering survival, warmer winters can instead disrupt these low-temperature trait-environment associations, with negative consequences for populations. While there is increasing evidence of physiological adaptation to contemporary warming during the growing season, the effects of winter warming on physiological traits are less clear. To address this knowledge gap, we performed a common garden experiment using relatively warm-adapted versus cold-adapted populations of the acorn ant, Temnothorax curvispinosus, sampled across an urban heat island gradient, to explore the effects of winter conditions on plasticity and evolution of physiological traits. We found no evidence of evolutionary divergence in chill coma recovery nor in metabolic rate at either of two test temperatures (4 and 10 °C). Although we found the expected plastic response of increased metabolic rate under the 10 °C acute test temperature as compared with the 4 °C test temperature, this plastic response, (i.e., the acute thermal sensitivity of metabolic rate), was not different across populations. Surprisingly, we found that winter-acclimated urban ant populations exhibited higher heat tolerance compared with rural ant populations, and that the magnitude of divergence was comparable to that observed among growing-season acclimated ants. Finally, we found no evidence of differences between populations with respect to changes in colony size from the beginning to the end of the overwintering experiment. Together, these findings indicate that despite the evolution of higher heat tolerance that is often accompanied by losses in low-temperature tolerance, urban acorn ants have retained several components of low-temperature physiological performance when assessed under ecologically relevant overwintering conditions. Our study suggests the importance of measuring physiological traits under seasonally-relevant conditions to understand the causes and consequences of evolutionary responses to contemporary warming.

Cold tolerance and diapause within and across trophic levels: Endoparasitic wasps and their fly host have similar phenotypes

Low temperatures associated with winter can limit the survival of organisms, especially ectotherms whose body temperature is similar to their environment. However, there is a gap in understanding how overwintering may vary among groups of species that interact closely, such as multiple parasitoid species that attack the same host insect. Here, we investigate cold tolerance and diapause phenotypes in three endoparasitoid wasps of the apple maggot fly Rhagoletis pomonella (Diptera: Tephritidae): Utetes canaliculatus, Diachasma alloeum, and Diachasmimorpha mellea (Hymenoptera: Braconidae). Using a combination of respirometry and eclosion tracking, we found that all three wasp species exhibited the same three diapause duration phenotypes as the fly host. Weak (short duration) diapause was rare, with <5 % of all three wasp species prematurely terminating diapause at 21 °C. Most D.mellea (93 %) entered a more intense (longer duration) diapause that did not terminate within 100 d at this warm temperature. The majority of U.canaliculatus (92 %) and D. alloeum (72 %) averted diapause (non-diapause) at 21 °C. There was limited interspecific variation in acute cold tolerance among the three wasp species: wasps and flies had similarly high survival (>87 %) following exposure to extreme low temperatures (-20 °C) as long as their body fluids did not freeze. The three wasp species also displayed little interspecific variation in survival following prolonged exposure to mild chilling of 8 or more weeks at 4 °C. Our study thus documents a remarkable conservation of cold tolerance and diapause phenotypes within and across trophic levels.

Rapid adaptation in a fast-changing world: Emerging insights from insect genomics

Many researchers have questioned the ability of biota to adapt to rapid anthropogenic environmental shifts. Here, we synthesize emerging genomic evidence for rapid insect evolution in response to human pressure. These new data reveal diverse genomic mechanisms (single locus, polygenic, structural shifts; introgression) underpinning rapid adaptive responses to a variety of anthropogenic selective pressures. While the effects of some human impacts (e.g. pollution; pesticides) have been previously documented, here we highlight startling new evidence for rapid evolutionary responses to additional anthropogenic processes such as deforestation. These recent findings indicate that diverse insect assemblages can indeed respond dynamically to major anthropogenic evolutionary challenges. Our synthesis also emphasizes the critical roles of genomic architecture, standing variation and gene flow in maintaining future adaptive potential. Broadly, it is clear that genomic approaches are essential for predicting, monitoring and responding to ongoing anthropogenic biodiversity shifts in a fast-changing world.

Molecular Mechanisms of Winter Survival

Winter provides many challenges for insects, including direct injury to tissues and energy drain due to low food availability. As a result, the geographic distribution of many species is tightly coupled to their ability to survive winter. In this review, we summarize molecular processes associated with winter survival, with a particular focus on coping with cold injury and energetic challenges. Anticipatory processes such as cold acclimation and diapause cause wholesale transcriptional reorganization that increases cold resistance and promotes cryoprotectant production and energy storage. Molecular responses to low temperature are also dynamic and include signaling events during and after a cold stressor to prevent and repair cold injury. In addition, we highlight mechanisms that are subject to selection as insects evolve to variable winter conditions. Based on current knowledge, despite common threads, molecular mechanisms of winter survival vary considerably across species, and taxonomic biases must be addressed to fully appreciate the mechanistic basis of winter survival across the insect phylogeny.

Current and lagged climate affects phenology across diverse taxonomic groups

The timing of life events (phenology) can be influenced by climate. Studies from around the world tell us that climate cues and species' responses can vary greatly. If variation in climate effects on phenology is strong within a single ecosystem, climate change could lead to ecological disruption, but detailed data from diverse taxa within a single ecosystem are rare. We collated first sighting and median activity within a high-elevation environment for plants, insects, birds, mammals and an amphibian across 45 years (1975-2020). We related 10 812 phenological events to climate data to determine the relative importance of climate effects on species' phenologies. We demonstrate significant variation in climate-phenology linkage across taxa in a single ecosystem. Both current and prior climate predicted changes in phenology. Taxa responded to some cues similarly, such as snowmelt date and spring temperatures; other cues affected phenology differently. For example, prior summer precipitation had no effect on most plants, delayed first activity of some insects, but advanced activity of the amphibian, some mammals, and birds. Comparing phenological responses of taxa at a single location, we find that important cues often differ among taxa, suggesting that changes to climate may disrupt synchrony of timing among taxa.

Developmental Differentiations of Major Maize Stemborers Due to Global Warming in Temperate and Tropical Climates

While many insects are in decline due to global warming, the effect of rising temperatures on crop insect pests is uncertain. A capacity to understand future changes in crop pest populations remains critical to ensure food security. Using temperature-dependent mathematical models of the development of four maize stemborers in temperate and tropical regions, we evaluated the potential impacts of different climate change scenarios on development time. While recognizing the limitations of the temperature-dependent development rate approach, we found that global warming could either be beneficial or detrimental to pest development, depending on the optimal temperature for the development of the species and scenarios of climate change. Expected responses range from null development to 1.5 times faster development than expected today. These results suggest that in the medium term, the studied species could benefit from global warming with an accelerated development, while in the long term, their development could either be delayed or accelerated, which may impact their dynamics with implications on maize cultivation.

Limited sex differences in plastic responses suggest evolutionary conservatism of thermal reaction norms: A meta-analysis in insects

Temperature has a profound effect on the growth and development of ectothermic animals. However, the extent to which ecologically driven selection pressures can adjust thermal plastic responses in growth schedules is not well understood. Comparing temperature-induced plastic responses between sexes provides a promising but underexploited approach to evaluating the evolvability of thermal reaction norms: males and females share largely the same genes and immature environments but typically experience different ecological selection pressures. We proceed from the idea that substantial sex differences in plastic responses could be interpreted as resulting from sex-specific life-history optimization, whereas similarity among the sexes should rather be seen as evidence of an essential role of physiological constraints. In this study, we performed a meta-analysis of sex-specific thermal responses in insect development times, using data on 161 species with comprehensive phylogenetic and ecological coverage. As a reference for judging the magnitude of sex specificity in thermal plasticity, we compared the magnitude of sex differences in plastic responses to temperature with those in response to diet. We show that sex-specific responses of development times to temperature variation are broadly similar. We also found no strong evidence for sex specificity in thermal responses to depend on the magnitude or direction of sex differences in development time. Sex differences in temperature-induced plastic responses were systematically less pronounced than sex differences in responses induced by variations in larval diet. Our results point to the existence of substantial constraints on the evolvability of thermal reaction norms in insects as the most likely explanation. If confirmed, the low evolvability of thermal response is an essential aspect to consider in predicting evolutionary responses to climate warming.

A quantitative synthesis of and predictive framework for studying winter warming effects in reptiles

Increases in temperature related to global warming have important implications for organismal fitness. For ectotherms inhabiting temperate regions, ‘winter warming’ is likely to be a key source of the thermal variation experienced in future years. Studies focusing on the active season predict largely positive responses to warming in the reptiles; however, overlooking potentially deleterious consequences of warming during the inactive season could lead to biased assessments of climate change vulnerability. Here, we review the overwinter ecology of reptiles, and test specific predictions about the effects of warming winters, by performing a meta-analysis of all studies testing winter warming effects on reptile traits to date. We collated information from observational studies measuring responses to natural variation in temperature in more than one winter season, and experimental studies which manipulated ambient temperature during the winter season. Available evidence supports that most reptiles will advance phenologies with rising winter temperatures, which could positively affect fitness by prolonging the active season although effects of these shifts are poorly understood. Conversely, evidence for shifts in survivorship and body condition in response to warming winters was equivocal, with disruptions to biological rhythms potentially leading to unforeseen fitness ramifications. Our results suggest that the effects of warming winters on reptile species are likely to be important but highlight the need for more data and greater integration of experimental and observational approaches. To improve future understanding, we recap major knowledge gaps in the published literature of winter warming effects in reptiles and outline a framework for future research.

The Resilience of Polar Collembola (Springtails) in a Changing Climate

Assessing the resilience of polar biota to climate change is essential for predicting the effects of changing environmental conditions for ecosystems. Collembola are abundant in terrestrial polar ecosystems and are integral to food-webs and soil nutrient cycling. Using available literature, we consider resistance (genetic diversity; behavioural avoidance and physiological tolerances; biotic interactions) and recovery potential for polar Collembola. Polar Collembola have high levels of genetic diversity, considerable capacity for behavioural avoidance, wide thermal tolerance ranges, physiological plasticity, generalist-opportunistic feeding habits and broad ecological niches. The biggest threats to the ongoing resistance of polar Collembola are increasing levels of dispersal (gene flow), increased mean and extreme temperatures, drought, changing biotic interactions, and the arrival and spread of invasive species. If resistance capacities are insufficient, numerous studies have highlighted that while some species can recover from disturbances quickly, complete community-level recovery is exceedingly slow. Species dwelling deeper in the soil profile may be less able to resist climate change and may not recover in ecologically realistic timescales given the current rate of climate change. Ultimately, diverse communities are more likely to have species or populations that are able to resist or recover from disturbances. While much of the Arctic has comparatively high levels of diversity and phenotypic plasticity; areas of Antarctica have extremely low levels of diversity and are potentially much more vulnerable to climate change.

Size at Birth, Postnatal Growth, and Reproductive Timing in an Australian Microbat

Reproductive phenology, size at birth, and postnatal growth are important life history traits that reflect parental investment. The ability to document detailed changes in these traits can be a valuable tool in the identification and management of at-risk wildlife populations. We examined reproductive traits in a common, widespread Australian microbat, Chalinolobus gouldii, at two sites over two years and derived growth curves and age estimation equations which will be useful in the study of how intrinsic and extrinsic factors alter parental investment strategies. We found that male and female offspring did not differ significantly in their size at birth or their postnatal growth rates. Bats born in 2018 were smaller at birth but grew at a faster rate than those born in 2017. When date of birth was compared across sites and years, we found bats born in 2018 had a later median birthdate (by 18 days) and births were more widespread than those born in 2017. Cooler and wetter weather during late gestation (Nov) in 2018 may have prolonged gestation and delayed births. With many bats facing threatening processes it is important to study reproductive plasticity in common and widespread “model” species, which may assist in the conservation and management of threatened microbats with similar reproductive traits.

Distribution and interaction of the suitable areas of Beauveria bassiana and Bactrocera dorsalis (Hendel)

Climate is a key factor affecting the potential distribution of insects, and the host is another important constraint for the distribution of pests. To elucidate changes in the potential distribution of Beauveria bassiana under climate change scenarios, this paper used the data of two different greenhouse gas (GHG) emission scenarios (RCP2.6, RCP8.5) to predict the potential distribution of B. bassiana and its typical host, Bactrocera dorsalis (Hendel), based on the MaxEnt model. Then, the potential distribution of B. bassiana and B. dorsalis (Hendel) was compared, and their suitable growth area’s change and expansion trend under two different GHG emission scenarios were mastered. The results of this study show that the potential distribution area of B. bassiana will increase by 2,050 under the RCP8.5 climate scenario, mainly in central Europe and southwestern Asia, with an increased area of 3.28 × 105 km2. However, under the climate scenario of RCP2.6, the potential distribution area for B. bassiana decreased by 2.0 × 105 km2, mainly in North America. This study will provide a theoretical basis for the control of B. dorsalis (Hendel) with B. bassiana.

Temperature-sensitive development shapes insect phenological responses to climate change

Phenological shifts vary within and among insect species and locations based on exposure and sensitivity to climate change. Shifts in environmental conditions and seasonal constraints along elevation and latitudinal gradients can select for differences in temperature sensitivity that generate differential phenological shifts. I examine the phenological implications of observed variation in developmental traits. Coupling physiological and ecological insight to link the environmental sensitivity of development to phenology and fitness offers promise in understanding variable phenological responses to climate change and their community and ecosystem implications. A key challenge in establishing these linkages is extrapolating controlled, laboratory experiments to temporally variable, natural environments. New lab and field experiments that incorporate realistic environmental variation are needed to test the extrapolations. Establishing the linkages can aid understanding and anticipating impacts of climate change on insects.

Winter bat activity: The role of wetlands as food and drinking reservoirs under climate change

Bat arousals during hibernation are related to rises in environmental temperature, body water loss and increasing body heat. Therefore, bats either hibernate in cold places or migrate to areas with mild winters to find water and insects to intake. During winter, insects are relatively abundant in wetlands with mild climates when low temperatures hamper insect activity in other places. However, the role of wetlands to sustain winter bat activity has never been fully assessed. To further understand bat behaviour during hibernation, we evaluated how the weather influenced hibernating bats, assessed the temperature threshold that increased bat arousals, and discussed how winter temperatures could affect bat activity under future climate change scenarios. The effects of weather and landscape composition on winter bat activity were assessed by acoustically sampling four different habitats (wetlands, rice paddies, urban areas and salt marshes) in the Ebro Delta (Spain). Our results show one of the highest winter bat foraging activities ever reported, with significantly higher activity in wetlands and urban areas. Most importantly, we found a substantial increase in bat activity triggered when nocturnal temperatures reached ca. 11 °C. By contrasting historical weather datasets, we show that, since the 1940s, there has been an increase by ca. 1.5 °C in winter maximum temperatures and a 180% increase in the number of nights with mean temperatures above 11 °C in the Ebro Delta. Temperature trends suggest that in 60-80 years, winter months will reach average temperatures of 11 °C (except maybe in January), which suggest a potential coming interruption or disappearance of bat hibernation in coastal Mediterranean habitats. This study highlights the significant role of wetlands in bat conservation under a climate change scenario as these humid areas represent one of the few remaining winter foraging habitats.

Global Warming and Its Implications on Nature Tourism at Phinda Private Game Reserve, South Africa

The past decade recorded the highest number of high impact extreme weather events such as flooding, rainfall events, fires, droughts, and heatwaves amongst others. One of the key features and drivers of extreme weather events has been global warming, with record temperatures recorded globally. The World Meteorological Organization indicated that the 2010–2020 decade was one of the warmest on record. Continued global warming triggers a chain of positive feedback with far-reaching adverse implications on the environment and socio-economic activities. The tourism industry fears that increased global warming would result in severe challenges for the sector. The challenges include species extinction, disruption of tourism aviation, and several tourism activities. Given the extent of climate variability and change, this study examines the impacts of rising temperatures on tourism operations at Phinda Private Game Reserve in South Africa. The study adopts a mixed-method approach that uses secondary, archival, and primary data collected through interviews and field observations to investigate the impacts. Data analysis was done using XLSTAT and Mann–Kendall Trend Analysis to analyse climate trends, while content and thematic analyses were used to analyse primary data findings. The study found that increasing temperature is challenging for tourists and tourism employees as it affects productivity, sleeping patterns, tourism operations, and infrastructure. High temperatures are a considerable threat to water availability and animal sightings, adversely affecting the game drive experience. Increased heatwaves resulted in bird mortality and hatching mortality for turtles; this is a significant conservation challenge. The study recommends that heat stress be treated as a health and safety issue to protect tourists and employees.

Host Gall Size and Temperature Influence Voltinism in an Exotic Parasitoid

Insect phenology is highly temperature-dependent. Higher temperatures can lead to earlier emergence and lengthening of the active period, which enable many insect groups to complete more generations. Studies on the effects of climate change on insect populations are providing concerning evidence supporting this relationship. These kind of shifts in phenology and voltinism also occur in agricultural and forest insect pests and their natural enemies, with potential implications for biological control. The consequences derived from changing temperature regimes on tritrophic interactions remain poorly studied, particularly in gall-inducing insects and their parasitoids. Here we detail the occurrence of bivoltinism in the exotic parasitoid Torymus sinensis, previously categorized as univoltine, a widely introduced species to fight against the invasive Asian chestnut gall wasp Dryocosmus kuriphilus wherever this pest spread. This plasticity in voltinism has been observed in the southernmost European distribution of D. kuriphilus, and appears to be mediated by both temperature and gall traits, namely size or the number of gall chambers. Bivoltinism was most common at annual mean temperatures around 13.5°C and in galls with more chambers. Through this work, we intend to unravel the factors behind this phenomenon and discern the possible consequences on host-parasitoid interactions.

Anoxia hormesis following overwintering diapause boosts bee survivorship and adult performance

Insect pollination is a crucial component of our ecosystems and biodiversity, but our reliance on this ecosystem service has much broader implications. We depend on these pollination services to produce materials and food. But insect pollinators, especially bees, are in strong decline due to a plethora of factors, least of which are environmental abiotic stressors like climate change. The alfalfa leafcutting bee, Megachile rotundata, is the world's most managed solitary bee and is particularly vulnerable to changes in temperature. This species spends up to ten months overwintering while being exposed to the lowest temperatures of winters and the hottest temperatures of late summer. This results in usage of energy reserves prematurely and asynchronous spring emergence with their food resource. To understand the stress response of these bees and potentially boost their performance, we applied a hormetic framework where bees were exposure to different doses of anoxia (the absence of oxygen) to trigger hormesis; a low-dose stimulatory response known to lower damage and improve performance. We used hormesis on immature bees as a post-winter treatment with the goal of improving springtime performance in adults. One hour of anoxia had no negative effect on adult springtime emergence and bees were quick to recover. These bees were more active than untreated bees, as resistant to starvation, and as long-lived. Higher exposure to anoxia (3 h) was found to be mildly hormetic and 6-h exposures were detrimental. Anoxia hormesis did not represent a significant cost on the energy reserve of overwintering bees but we found that the age at which anoxia is applied will affect the effectiveness of treatment. Our data suggest that anoxia hormesis is a viable intervention to improve springtime performance in overwintering bees.

Metabolic Response of Aphid Cinara tujafilina to Cold Stress

Climate changes enable thermophilic insect species to expand their ranges, but also force them to adapt to unfavourable environmental conditions in new habitats. Focusing on Cinara tujafilina, we investigated the metabolic changes in the body of the aphid that enabled it to survive the low temperatures of winter. Using GC–MS analysis, differences in the chemical composition of the aphids in summer and winter were found. The metabolic changes were mainly related to the increased activity of the pathways of carbohydrate metabolism, such as glycolysis and the pentose phosphate pathway; a decrease in tricarboxylic acid cycle (TCA); accumulation of polyols; and increased levels of proline, tyrosine, and fatty acids.

Snow modulates winter energy use and cold exposure across an elevation gradient in a montane ectotherm

Snow insulates the soil from air temperature, decreasing winter cold stress and altering energy use for organisms that overwinter in the soil. As climate change alters snowpack and air temperatures, it is critical to account for the role of snow in modulating vulnerability to winter climate change. Along elevational gradients in snowy mountains, snow cover increases but air temperature decreases, and it is unknown how these opposing gradients impact performance and fitness of organisms overwintering in the soil. We developed experimentally validated ecophysiological models of cold and energy stress over the past decade for the montane leaf beetle Chrysomela aeneicollis, along five replicated elevational transects in the Sierra Nevada mountains in California. Cold stress peaks at mid-elevations, while high elevations are buffered by persistent snow cover, even in dry years. While protective against cold, snow increases energy stress for overwintering beetles, particularly at low elevations, potentially leading to mortality or energetic tradeoffs. Declining snowpack will predominantly impact mid-elevation populations by increasing cold exposure, while high elevation habitats may provide refugia as drier winters become more common.

Phenology dictates the impact of climate change on geographic distributions of six co-occurring North American grasshoppers

Throughout the last century, climate change has altered the geographic distributions of many species. Insects, in particular, vary in their ability to track changing climates, and it is likely that phenology is an important determinant of how well insects can either expand or shift their geographic distributions in response to climate change. Grasshoppers are an ideal group to test the hypothesis that phenology correlates with range expansion, given that co-occurring confamilial, and even congeneric, species can differ in phenology. Here, I tested the hypothesis that early- and late-season species should possess different range expansion potentials, as estimated by habitat suitability from ecological niche models. I used nine different modeling techniques to estimate habitat suitability of six grasshopper species of varying phenology under two climate scenarios for the year 2050. My results suggest that, of the six species examined here, early-season species were more sensitive to climate change than late-season species. The three early-season species examined here might shift northward during the spring, while the modeled geographic distributions of the three late-season species were generally constant under climate change, likely because they were pre-adapted to hot and dry conditions. Phenology might therefore be a good predictor of how insect distributions might change in the future, but this hypothesis remains to be tested at a broader scale.

Seasonal dynamics of Diptera in individual biotopes in the center of the European part of Russia

In a changing climate, phenological observations are gaining new importance. They can tell what changes are taking place in certain environmental conditions. The studies were conducted in 2019 within the territory of the Republic of Mordovia (the center of the European part of Russia). Beer traps (beer as a bait) were used to collect Diptera. The material was collected in the period from April to October in different forest biotopes (pine forest, lime forest, aspen forest, birch forest and oak forest) and the air temperature was recorded at the same time. In total, more than 14.000 specimens of Diptera were recorded. Overall, 29 families were recorded. The largest number of families was observed for birch (23 families) and pine (24 families) forests, the smallest number – in aspen forest (16 families). The families Muscidae, Drosophilidae, Calliphoridae had the largest number of captured individuals (44.5%, 35.2%, 7.6% of the total number of individuals respectively). The highest number of individuals was captured in oak forest. The dynamics of abundance in all biotopes were similar and were characterized by the same number of declines and rises. The first small significant peak in the number of Diptera occurred in the first half of summer. A slight increase in the number of specimenі occurred in mid-June. In the second half of September, there was a gradual increase in the number and the maximum peak was recorded in mid-October, then there was a decline. The autumn increase in the number of Diptera in all five biotopes exceeded the summer peak by several times. This dynamic was typical for most families. However, species from the family Lonchaeidae had the peak in July. For our better understanding of the changes in the seasonal dynamics of the number of Diptera, long-term observations in different climatic zones are needed.

Seasonal dynamics of Diptera in individual biotopes in the center of the European part of Russia

In a changing climate, phenological observations are gaining new importance. They can tell what changes are taking place in certain environmental conditions. The studies were conducted in 2019 within the territory of the Republic of Mordovia (the center of the European part of Russia). Beer traps (beer as a bait) were used to collect Diptera. The material was collected in the period from April to October in different forest biotopes (pine forest, lime forest, aspen forest, birch forest and oak forest) and the air temperature was recorded at the same time. In total, more than 14.000 specimens of Diptera were recorded. Overall, 29 families were recorded. The largest number of families was observed for birch (23 families) and pine (24 families) forests, the smallest number – in aspen forest (16 families). The families Muscidae, Drosophilidae, Calliphoridae had the largest number of captured individuals (44.5%, 35.2%, 7.6% of the total number of individuals respectively). The highest number of individuals was captured in oak forest. The dynamics of abundance in all biotopes were similar and were characterized by the same number of declines and rises. The first small significant peak in the number of Diptera occurred in the first half of summer. A slight increase in the number of specimenі occurred in mid-June. In the second half of September, there was a gradual increase in the number and the maximum peak was recorded in mid-October, then there was a decline. The autumn increase in the number of Diptera in all five biotopes exceeded the summer peak by several times. This dynamic was typical for most families. However, species from the family Lonchaeidae had the peak in July. For our better understanding of the changes in the seasonal dynamics of the number of Diptera, long-term observations in different climatic zones are needed.

Resistance and survival to extreme heat shows circadian and sex-specific patterns in A cavity nesting bee

The pollination services provided by insects have been a crucial part of evolution and survival for many species, including humans. For bees to be efficient pollinators they must survive the environmental insults they face daily. Thus, looking into the short- and long-term effects of heat exposure on bee performance provides us with a foundation for investigating how stress can affect insect pollination. Solitary bees are a great model for investigating the effects of environmental stress on pollinators because the vast majority of insect pollinator species are solitary rather than social. One of the most pervasive environmental stressors to insects is temperature. Here we investigated how a one-hour heat shock affected multiple metrics of performance in the alfalfa leafcutting bee, Megachile rotundata. We found that a short heat shock (1hr at 45°C) can delay adult emergence in males but not females. Bee pupae were rather resilient to a range of high temperature exposures that larvae did not survive. Following heat shock (1hr at 50°C), adult bees were drastically less active than untreated bees, and this reduction in activity was evident over several days. Heat shock also led to a decrease in bee survival and longevity. Additionally, we found a connection between starvation survival after heat shock and time of exposure, where bees exposed in the morning survived longer than those exposed in the afternoon, when they would normally experience heat shock in the field. These data suggest that there is an unexplored daily/circadian component to the stress response in bees likely similar to that seen in flies, nematodes, and plants which is constitutive or preemptive rather than restorative. Taken together our data indicate that single heat shock events have strong potential to negatively impact multiple life history traits correlated with reproduction and fitness.

The complexity of global change and its effects on insects

Global change includes multiple overlapping and interacting drivers: 1) climate change, 2) land use change, 3) novel chemicals, and 4) the increased global transport of organisms. Recent studies have documented the complex and counterintuitive effects of these drivers on the behavior, life histories, distributions, and abundances of insects. This complexity arises from the indeterminacy of indirect, non-additive and combined effects. While there is wide consensus that global change is reorganizing communities, the available data are limited. As the pace of anthropogenic changes outstrips our ability to document its impacts, ongoing change may lead to increasingly unpredictable outcomes. This complexity and uncertainty argue for renewed efforts to address the fundamental drivers of global change.

Direct and indirect effects of altered temperature regimes and phenological mismatches on insect populations

Climate change is transforming ecosystems by altering species ranges, the composition of communities, and trophic interactions. Here, we synthesize recent reviews and subsequent developments to provide an overview of insect ecological and evolutionary responses to altered temperature regimes. We discuss both direct responses to thermal stress and indirect responses arising from phenological mismatches, altered host quality, and changes in natural enemy activity. Altered temperature regimes can increase exposure to both cold and heat stress and result in phenological and morphological mismatches with adjacent trophic levels. Host plant quality varies in a heterogenous way in response to altered temperatures with both increases and decreases observed. Density-dependent effects, spatial heterogeneity, and rapid evolutionary change provide some resilience to these threats.

The HSP/co-chaperone network in environmental cold adaptation of Chilo suppressalis

Winter cold is one of the major environmental stresses for ectotherm species. Chilo suppressalis, a notorious lepidopteran pest of rice, has a wide geographic region that includes temperate zones with severe environmental conditions. Although C. suppressalis exhibits remarkable cold tolerance, its cold-adaptation mechanisms remain unclear. Here, we used bioinformatics approaches to evaluate transcript levels of genes comprising the C. suppressalis heat shock protein (HSP)/co-chaperone network in response to cold-induced stress. Using all such genes identified in the C. suppressalis genome, we experimentally examined the corresponding transcript levels under cold-acclimation or intermittent cold-shock stresses in diapause and non-diapausing larvae. In total, we identified 19 HSPs and 8 HSP co-chaperones in the C. suppressalis genome. Nine (hsp90, hsp75, hsp70, hsp40, small hsp, activator of 90 kDa heat shock protein ATPase-like, heat shock factor, heat shock factor binding protein 1-like and HSPB1-associated protein 1) were highly cold-inducible and likely comprise the principal cold-response HSP/co-chaperone network in C. suppressalis. We also found that transcriptional regulation of the HSP/co-chaperone networks response differs between cold-acclimation and short-term cold-shock. Moreover, activation of the HSP/co-chaperone network depends on the diapause state of overwintering larvae and cold acclimation may further increase larval cold tolerance. These results provide key new insights in the cold-adaptation mechanisms in C. suppressalis.

Plasticity of cold hardiness in the eastern spruce budworm, Choristoneura fumiferana

High latitude insect populations must cope with extreme conditions, particularly low temperatures. Insects use a variety of cold hardiness mechanisms to withstand this temperature stress, and these can drive geographic distributions through overwintering mortality. The degree of cold hardiness can be altered by two evolved responses: phenotypic plasticity and local adaptation. Phenotypic plasticity can occur within or between generations (transgenerational plasticity; TGP), and local adaptation can evolve through directional selection in response to regional climatic differences. We used the eastern spruce budworm, Choristoneura fumiferana (Lepidoptera: Tortricidae) as a model to explore the role that variable winter temperatures play in inducing two aspects of plasticity in cold hardiness: TGP and local adaptation in phenotypic plasticity. This species is one of the most destructive boreal forest pests in North America, therefore accurately predicting overwintering survival is essential for effective management. While we found no evidence of TGP in cold hardiness, there was a long term fitness cost to larvae that experienced repeated cold exposures. We also found evidence of local adaptation in both seasonal and short-term plasticity of cold hardiness, as our more northerly populations that would experience lower overwintering temperatures had more plastic responses to cold exposure. These findings provide evidence for the importance of phenotypic plasticity and local adaptation when modelling species distributions.