What Can Plasticity Contribute to Insect Responses to Climate Change?

Thermal limits in the face of infectious disease: How important are pathogens?

The frequency and severity of both extreme thermal events and disease outbreaks are predicted to continue to shift as a consequence of global change. As a result, species persistence will likely be increasingly dependent on the interaction between thermal stress and pathogen exposure. Missing from the intersection between studies of infectious disease and thermal ecology, however, is the capacity for pathogen exposure to directly disrupt a host's ability to cope with thermal stress. Common sources of variation in host thermal performance, which are likely to interact with infection, are also often unaccounted for when assessing either the vulnerability of species or the potential for disease spread during extreme thermal events. Here, we describe how infection can directly alter host thermal limits, to a degree that exceeds the level of variation commonly seen across species large geographic distributions and that equals the detrimental impact of other ecologically relevant stressors. We then discuss various sources of heterogeneity within and between populations that are likely to be important in mediating the impact that infection has on variation in host thermal limits. In doing so we highlight how infection is a widespread and important source of variation in host thermal performance, which will have implications for both the persistence and vulnerability of species and the dynamics and transmission of disease in a more thermally extreme world.

Developmental Temperature Affects Life-History Traits and Heat Tolerance in the Aphid Parasitoid Aphidius colemani

Developmental temperature plays important roles in the expression of insect traits through thermal developmental plasticity. We exposed the aphid parasitoid Aphidius colemani to different temperature regimes (10, 20, or 28 °C) throughout larval development and studied the expression of morphological and physiological traits indicator of fitness and heat tolerance in the adult. We showed that the mass decreased and the surface to volume ratio of parasitoids increased with the development temperature. Water content was not affected by rearing temperature, but parasitoids accumulated more lipids when reared at 20 °C. Egg content was not affected by developmental temperature, but adult survival was better for parasitoids reared at 20 °C. Finally, parasitoids developed at 20 °C showed the highest heat stupor threshold, whereas parasitoids developed at 28 °C showed the highest heat coma threshold (better heat tolerance CTmax1 and CTmax2, respectively), therefore only partly supporting the beneficial acclimation hypothesis. From a fundamental point of view, our study highlights the role of thermal plasticity (adaptive or not) on the expression of different life history traits in insects and the possible correlations that exist between these traits. From an applied perspective, these results are important in the context of biological control through mass release techniques of parasitoids in hot environments.

Effects of Thermal Acclimation on the Tolerance of Bactrocera zonata (Diptera: Tephritidae) to Hydric Stress

Insects, similarly to other small terrestrial invertebrates, are particularly susceptible to climatic stress. Physiological adjustments to cope with the environment (i.e., acclimation) together with genetic makeup eventually determine the tolerance of a species to climatic extremes, and constrain its distribution. Temperature and desiccation resistance in insects are both conditioned by acclimation and may be interconnected, particularly for species inhabiting xeric environments. We determined the effect of temperature acclimation on desiccation resistance of the peach fruit fly (Bactrocera zonata, Tephritidae) – an invasive, polyphagous pest, currently spreading through both xeric and mesic environments in Africa and the Eurasian continent. Following acclimation at three constant temperatures (20, 25, and 30°C), the survival of adult flies deprived of food and water was monitored in extreme dry and humid conditions (<10 and >90% relative humidity, respectively). We found that flies acclimated at higher temperatures were significantly heavier, and contained more lipids and protein. Acclimation temperature significantly and similarly affected the survival of males and females at both high and low humidity conditions. In both cases, flies maintained at 30°C survived longer compared to 20 and 25°C – habituated counterparts. Regardless of the effect of acclimation temperature on survival, overall life expectancy was significantly shortened when flies were assayed under desiccating conditions. Additionally, our experiments indicate no significant difference in survival patterns between males and females, and that acclimation temperature had similar effects after both short (5–10 days) and long (11–20 days) acclimation periods. We conclude that acclimation at 30°C prolongs the survival of B. zonata, regardless of ambient humidity levels. Temperature probably affected survival through modulating feeding and metabolism, allowing for accumulation of larger energetic reserves, which in turn, promoted a greater ability to resist starvation, and possibly desiccation as well. Our study set the grounds for understanding the phenotypic plasticity of B. zonata from the hydric perspective, and for further evaluating the invasion potential of this pest.

Heightened among-individual variation in life history but not morphology is related to developmental temperature in reptiles

Increases in phenotypic variation under extreme (e.g. novel or stressful) environmental conditions are emerging as a crucial process through which evolutionary adaptation can occur. Lack of prior stabilizing selection, as well as potential instability of developmental processes in these environments, may lead to a release of phenotypic variation that can have important evolutionary consequences. Although such patterns have been shown in model study organisms, we know little about the generality of trait variance across environments for non-model organisms. Here, we test whether extreme developmental temperatures increase the phenotypic variation across diverse reptile taxa. We find that the among-individual variation in a key life-history trait (post-hatching growth) increases at extreme cold and hot temperatures. However, variations in two measures of hatchling morphology and in hatchling performance were not related to developmental temperature. Although extreme developmental temperatures may increase the variation in growth, our results suggest that plastic responses to stressful incubation conditions do not generally make more extreme phenotypes available to selection. We discuss the reasons for the general lack of increased variability at extreme incubation temperatures and the implications this has for local adaptation in hatchling morphology and physiology.

Transgenerational exposure to warming reduces the sensitivity to a pesticide under warming

Despite the increased attention for temporal aspects of stressor interactions and for effects of warming in ecotoxicological studies, we lack knowledge on how different exposure durations to warming may affect pesticide sensitivity. We tested how three types of exposure duration to 4 °C warming (acute, developmental and transgenerational exposure to 24 °C vs 20 °C) shape the effect of the pesticide chlorpyrifos on two ecologically relevant fitness-related traits of mosquito larvae: heat tolerance and antipredator behaviour. Transgenerational (from the parental generation) and developmental (from the egg stage) warming appeared energetically more stressful than acute warming (from the final instar), because (i) only the latter resulted in an adaptive increase of heat tolerance, and (ii) especially developmental and transgenerational warming reduced the diving responsiveness and diving time. Exposure to chlorpyrifos decreased the heat tolerance, diving responsiveness and diving time. The impact of chlorpyrifos was lower at 24 °C than at 20 °C indicating that the expected increase in toxicity at 24 °C was overruled by the observed increase in pesticide degradation. Notably, although our results suggest that transgenerational warming was energetically more stressful, it did reduce the chlorpyrifos-induced negative effects at 24 °C on heat tolerance and the alarm escape response compared to acute warming. Our results provide important evidence that the exposure duration to warming may determine the impact of a pesticide under warming, thereby identifying a novel temporal aspect of stressor interactions in risk assessment.

Bumblebee resilience to climate change, through plastic and adaptive responses

Bumblebees are ubiquitous, cold-adapted eusocial bees found worldwide from subarctic to tropical regions of the world. They are key pollinators in most temperate and boreal ecosystems, and both wild and managed populations are significant contributors to agricultural pollination services. Despite their broad ecological niche at the genus level, bumblebee species are threatened by climate change, particularly by rising average temperatures, intensifying seasonality and the increasing frequency of extreme weather events. While some temperature extremes may be offset at the individual or colony level through temperature regulation, most bumblebees are expected to exhibit specific plastic responses, selection in various key traits, and/or range contractions under even the mildest climate change. In this review, we provide an in-depth and up-to-date review on the various ways by which bumblebees overcome the threats associated with current and future global change. We use examples relevant to the fields of bumblebee physiology, morphology, behaviour, phenology, and dispersal to illustrate and discuss the contours of this new theoretical framework. Furthermore, we speculate on the extent to which adaptive responses to climate change may be influenced by bumblebees' capacity to disperse and track suitable climate conditions. Closing the knowledge gap and improving our understanding of bumblebees' adaptability or avoidance behaviour to different climatic circumstances will be necessary to improve current species climate response models. These models are essential to make correct predictions of species vulnerability in the face of future climate change and human-induced environmental changes to unfold appropriate future conservation strategies.

Thermal limits and preferences of large branchiopods (Branchiopoda: Anostraca and Spinicaudata) from temporary wetland arid zone systems

Large branchiopods are specialist crustaceans adapted for life in temporary, thermally dynamic wetland ecosystems. Certain large branchiopod species are, however, restricted to specific temporary wetland types, exemplified by their physico-chemical and hydroperiod characteristics. Here, we contrasted the thermal preference and critical thermal maxima (CT_max) and minima (CT_min) of southern African anostracans and spinicaudatans found exclusively in either temporary rock-pool or pan wetland types. We hypothesized that environment of origin would be a good predictor of thermal preference and critical thermal limits. To test this, Branchiopodopsis tridens (Anostraca) and Leptestheria brevirostris (Spinicaudata) were collected from rock-pool habitats, while Streptocephalus cafer (Anostraca) and a Gondwanalimnadia sp. (Spinicaudata) were collected from pan habitats. In contrast to our hypothesis, taxonomic relatedness was a better predictor of CT_max and temperature preference than environment of origin. Spinicaudatans were significantly more tolerant of high temperatures than anostracans, with L. brevirostris and Gondwanalimnadia sp. median CT_max values of 45.1 °C and 44.1 °C, respectively, followed by S. cafer (42.8 °C) and B. tridens (41.4 °C). Neither environment or taxonomic relatedness were good predictors of CT_min trends, with B. tridens (0.9 °C) and Gondwanalimnadia sp. (2.1 °C) having the lowest median CT_min values, followed by L. brevirostris (3.4 °C) and S. cafer (3.6 °C). On the contrary, temperature preferences differed according to taxa, with spinicaudatans significantly preferring higher temperatures than anostracans. Leptestheria brevirostris and Gondwanalimnadia sp. both spent most time at temperatures 30-32 °C, S. cafer at 18-20 °C and B. tridens at 21-23 °C. Constrained thermal traits reported here suggest that the studied anostracans might be more susceptible to projected climatic warming than the spinicaudatans, irrespective of habitat type, however, these taxa may also compensate through phenotypic plasticity.

Phenotypic plasticity as a cause and consequence of population dynamics

Predicting complex species-environment interactions is crucial for guiding conservation and mitigation strategies in a dynamically changing world. Phenotypic plasticity is a mechanism of trait variation that determines how individuals and populations adapt to changing and novel environments. For individuals, the effects of phenotypic plasticity can be quantified by measuring environment-trait relationships, but it is often difficult to predict how phenotypic plasticity affects populations. The assumption that environment-trait relationships validated for individuals indicate how populations respond to environmental change is commonly made without sufficient justification. Here we derive a novel general mathematical framework linking trait variation due to phenotypic plasticity to population dynamics. Applying the framework to the classical example of Nicholson's blowflies, we show how seemingly sensible predictions made from environment-trait relationships do not generalise to population responses. As a consequence, trait-based analyses that do not incorporate population feedbacks risk mischaracterising the effect of environmental change on populations.

Negative relationship between thermal tolerance and plasticity in tolerance emerges during experimental evolution in a widespread marine invertebrate

Whether populations can adapt to predicted climate change conditions, and how rapidly, are critical questions for the management of natural systems. Experimental evolution has become an important tool to answer these questions. In order to provide useful, realistic insights into the adaptive response of populations to climate change, there needs to be careful consideration of how genetic differentiation and phenotypic plasticity interact to generate observed phenotypic changes. We exposed three populations of the widespread copepod Acartia tonsa (Crustacea) to chronic, sublethal temperature selection for 15 generations. We generated thermal survivorship curves at regular intervals both during and after this period of selection to track the evolution of thermal tolerance. Using reciprocal transplants between ambient and warming conditions, we also tracked changes in the strength of phenotypic plasticity in thermal tolerance. We observed significant increases in thermal tolerance in the Warming lineages, while plasticity in thermal tolerance was strongly reduced. We suggest these changes are driven by a negative relationship between thermal tolerance and plasticity in thermal tolerance. Our results indicate that adaptation to warming through an increase in thermal tolerance might not reduce vulnerability to climate change if the increase comes at the expense of tolerance plasticity. These results illustrate the importance of considering changes in both a trait of interest and the trait plasticity during experimental evolution.

Local climate adaptation and gene flow in the native range of two co-occurring fruit moths with contrasting invasiveness

Invasive species pose increasing threats to global biodiversity and ecosystems. While previous studies have characterized successful invaders based on ecological traits, characteristics related to evolutionary processes have rarely been investigated. Here we compared gene flow and local adaptation using demographic analyses and outlier tests in two co-occurring moth pests across their common native range of China, one of which (the peach fruit moth, Carposina sasakii) has maintained its native distribution, while the other (the oriental fruit moth, Grapholita molesta) has expanded its range globally during the past century. We found that both species showed a pattern of genetic differentiation and an evolutionary history consistent with a common southwestern origin and northward expansion in their native range. However, for the noninvasive species, genetic differentiation was closely aligned with the environment, and there was a relatively low level of gene flow, whereas in the invasive species, genetic differentiation was associated with geography. Genome scans indicated stronger patterns of climate-associated loci in the noninvasive species. While strong local adaptation and reduced gene flow across its native range may have decreased the invasiveness of C. sasakii, this requires further validation with additional comparisons of invasive and noninvasive species across their native range.

The ecophysiological plasticity of Aedes aegypti and Aedes albopictus concerning overwintering in cooler ecoregions is driven by local climate and acclimation capacity

Aedes aegypti and Aedes albopictus transmit diseases such as dengue, and are of major public health concern. Driven by climate change and global trade/travel both species have recently spread to new tropic/subtropic regions and Ae. albopictus also to temperate ecoregions. The capacity of both species to adapt to new environments depends on their ecophysiological plasticity, which is the width of functional niches where a species can survive. Mechanistic distribution models often neglect to incorporate ecophysiological plasticity especially in regards to overwintering capacity in cooler habitats. To portray the ecophysiological plasticity concerning overwintering capability, we conducted temperature experiments with multiple populations of both species originating from an altitudinal gradient in South Asia and tested as follows: the cold tolerance of eggs (-2 °C- 8 days and - 6 °C- 2 days) without and with an experimental winter onset (acclimation: 10 °C- 60 days), differences between a South Asian and a European Ae. albopictus population and the temperature response in life cycles (13 °C, 18 °C, 23 °C, 28 °C). Ecophysiological plasticity in overwintering capacity in Ae. aegypti is high in populations originating from low altitude and in Ae. albopictus populations from high altitude. Overall, ecophysiological plasticity is higher in Ae. albopictus compared to Ae. aegypti. In both species acclimation and in Ae. albopictus temperate continental origin had a huge positive effect on survival. Our results indicate that future mechanistic prediction models can include data on winter survivorship of both, tropic and subtropic Ae. aegypti, whereas for Ae. albopictus this depends on the respective temperate, tropical region the model is focusing on. Future research should address cold tolerance in multiple populations worldwide to evaluate the full potential of the ecophysiological plasticity in the two species. Furthermore, we found that Ae. aegypti can survive winter cold especially when acclimated and will probably further spread to colder ecoregions driven by climate change.

Spider Mites Singly Infected With Either Wolbachia or Spiroplasma Have Reduced Thermal Tolerance

Heritable symbionts play an essential role in many aspects of host ecology in a temperature-dependent manner. However, how temperature impacts the host and their interaction with endosymbionts remains largely unknown. Here, we investigated the impact of moderate (20°C) and high (30 and 35°C) temperatures on symbioses between the spider mite Tetranychus truncatus and two maternally inherited endosymbionts (Wolbachia and Spiroplasma). We found that the thermal tolerance of mites (as measured by survival after heat exposure) was lower for mites that were singly infected with either Wolbachia or Spiroplasma than it was for co-infected or uninfected mites. Although a relatively high temperature (30°C) is thought to promote bacterial replication, rearing at high temperature (35°C) resulted in losses of Wolbachia and particularly Spiroplasma. Exposing the mites to 20°C reduced the density and transmission of Spiroplasma but not Wolbachia. The four spider mite strains tested differed in the numbers of heat shock genes (Hsps) induced under moderate or high temperature exposure. In thermal preference (Tp) assays, the two Wolbachia-infected spider mite strains preferred a lower temperature than strains without Wolbachia. Our results show that endosymbiont-mediated spider mite responses to temperature stress are complex, involving a combination of changing endosymbiont infection patterns, altered thermoregulatory behavior, and transcription responses.

Insects and their pathogens in a changing climate

The complex nature of climate change-mediated multitrophic interaction is an underexplored area, but has the potential to dramatically shift transmission and distribution of many insects and their pathogens, placing some populations closer to the brink of extinction. However, for individual insect-pathogen interactions climate change will have complicated hard-to-anticipate impacts. Thus, both pathogen virulence and insect host immunity are intrinsically linked with generalized stress responses, and in both pathogen and host have extensive trade-offs with nutrition (e.g., host plant quality), growth and reproduction. Potentially alleviating or exasperating these impacts, some pathogens and hosts respond genetically and rapidly to environmental shifts. This review identifies many areas for future research including a particular need to identify how altered global warming interacts with other environmental changes and stressors, and how consistent these impacts are across pathogens and hosts. With that achieved we would be closer to producing an overarching framework to integrate knowledge on all environmental interplay and infectious disease events.

A meta-analysis of responses in floral traits and flower-visitor interactions to water deficit

Alterations in water availability and drought events as predicted by climate change scenarios will increasingly impact natural communities with effects already emerging at present. Water deficit leads to increasing physiological stress in plants, likely affecting floral development and causing changes in floral morphology, nectar and pollen production or scent. Understanding how these floral traits are altered by water deficit is necessary to predict changes in plant-pollinator interactions and how communities are impacted in the future. Here we employ a meta-analysis approach to synthesize the current evidence of experimental water deficit on floral traits and plant-pollinator interactions. Furthermore, we explore experimental factors potentially increasing heterogeneity between studies and provide ideas how to enhance comparability between studies. In the end, we highlight future directions and knowledge gaps for floral traits and plant-pollinator interactions under water deficit. Our analysis showed consistent decreases in floral size, number of flowers and nectar volume to reduced water availability. Other floral traits such as the start of flowering or herkogamy showed no consistent pattern. This indicates that effects of reduced water availability differ between specific traits that are potentially involved in different functions such as pollinator attraction or efficiency. We found no general decreasing visitation rates with water deficit for flower-visitor interactions. Furthermore, the comparison of available studies suggests that increased reporting of plant stress severity and including more hydraulic and physiological measurements will improve the comparability across experiments and aid a more mechanistic understanding of plant-pollinator interactions under altered environmental conditions. Overall, our results show that water deficit has the potential to strongly affect plant-pollinator interactions via changes in specific floral traits. Linking these changes to pollination services and pollinator performance is one crucial step for understanding how changing water availability and drought events under climate change will alter plant and pollinator communities.

Changes in the structure and composition of the 'Mexical' scrubland bee community along an elevational gradient

'Mexical' scrubland is a sclerophyllous evergreen Mediterranean-like vegetation occurring in the leeward slopes of the main Mexican mountain ranges, under tropical climate. This biome occupies an elevational range approximately from 1900 to 2600 meters above sea level, which frequently is the upper-most part of the mountains range. This puts it at risk of extinction in a scenario of global warming in which an upward retraction of this type of vegetation is expected. The Mexical remains one of the least studied ecosystems in Mexico. For instance, nothing is known about pollinator fauna of this vegetation. Our main objective is to make a first insight into the taxonomic identity of the bee fauna that inhabits this biome, and to study how it is distributed along the elevational gradient that it occupies. Our results highlight that elevation gradient negatively affects bee species richness and that this relationship is strongly mediated by temperature. Bee abundance had no significant pattern along elevational gradient, but shows a significant relationship with flower density. Interestingly, and contrary to previous works, we obtained a different pattern for bee richness and bee abundance. Bee community composition changed strongly along elevation gradient, mainly in relation to temperature and flower density. In a global warming scenario, as temperatures increases, species with cold preferences, occupying the highest part of the elevation gradient, are likely to suffer negative consequences (even extinction risk), if they are not flexible enough to adjust their physiology and/or some life-story traits to warmer conditions. Species occupying mid and lower elevations are likely to extend their range of elevational distribution towards higher ranges. This will foreseeably cause a new composition of species and a new scenario of interactions, the adjustment of which still leaves many unknowns to solve.

Identification of a neural basis for cold acclimation in Drosophila larvae

Low temperatures can be fatal to insects, but many species have evolved the ability to cold acclimate, thereby increasing their cold tolerance. It has been previously shown that Drosophila melanogaster larvae perform cold-evoked behaviors under the control of noxious cold-sensing neurons (nociceptors), but it is unknown how the nervous system might participate in cold tolerance. Herein, we describe cold-nociceptive behavior among 11 drosophilid species; we find that the predominant cold-evoked larval response is a head-to-tail contraction behavior, which is likely inherited from a common ancestor, but is unlikely to be protective. We therefore tested the hypothesis that cold nociception functions to protect larvae by triggering cold acclimation. We found that Drosophila melanogaster Class III nociceptors are sensitized by and critical to cold acclimation and that cold acclimation can be optogenetically evoked, sans cold. Collectively, these findings demonstrate that cold nociception constitutes a peripheral neural basis for Drosophila larval cold acclimation.

Predator-Induced Plasticity on Warning Signal and Larval Life-History Traits of the Aposematic Wood Tiger Moth, Arctia plantaginis

Predator-induced plasticity in life-history and antipredator traits during the larval period has been extensively studied in organisms with complex life-histories. However, it is unclear whether different levels of predation could induce warning signals in aposematic organisms. Here, we investigated whether predator-simulated handling affects warning coloration and life-history traits in the aposematic wood tiger moth larva, Arctia plantaginis. As juveniles, a larger orange patch on an otherwise black body signifies a more efficient warning signal against predators but this comes at the costs of conspicuousness and thermoregulation. Given this, one would expect that an increase in predation risk would induce flexible expression of the orange patch. Prior research in this system points to plastic effects being important as a response to environmental changes for life history traits, but we had yet to assess whether this was the case for predation risk, a key driver of this species evolution. Using a full-sib rearing design, in which individuals were reared in the presence and absence of a non-lethal simulated bird attack, we evaluated flexible responses of warning signal size (number of orange segments), growth, molting events, and development time in wood tiger moths. All measured traits except development time showed a significant response to predation. Larvae from the predation treatment developed a more melanized warning signal (smaller orange patch), reached a smaller body size, and molted more often. Our results suggest plasticity is indeed important in aposematic organisms, but in this case may be complicated by the trade-off between costly pigmentation and other life-history traits.

Additive and non-additive effects of day and night temperatures on thermally plastic traits in a model for adaptive seasonal plasticity

Developmental plasticity can match organismal phenotypes to ecological conditions, helping populations to deal with the environmental heterogeneity of alternating seasons. In contrast to natural situations, experimental studies of plasticity often use environmental conditions that are held constant during development. To explore potential interactions between day and night temperatures, we tested effects of circadian temperature fluctuations on thermally plastic traits in a seasonally plastic butterfly, Bicyclus anynana. Comparing phenotypes for four treatments corresponding to a full-factorial analysis of cooler and warmer temperatures, we found evidence of significant interaction effects between day and night temperatures. We then focused on comparing phenotypes between individuals reared under two types of temperature fluctuations (warmer days with cooler nights, and cooler days with warmer nights) and individuals reared under a constant temperature of the same daily mean. We found evidence of additive-like effects (for body size), and different types of dominance-like effects, with one particular period of the light cycle (for development time) or one particular extreme temperature (for eyespot size) having a larger impact on phenotype. Differences between thermally plastic traits, which together underlie alternative seasonal strategies for survival and reproduction, revealed their independent responses to temperature. This study underscores the value of studying how organisms integrate complex environmental information toward a complete understanding of natural phenotypic variation and of the impact of environmental change thereon.

Transgenerational phenotypic plasticity of diapause induction and related fitness cost in a commercial strain of the parasitoid Aphidius ervi Haliday

Diapause is an adaptation that insects have evolved to synchronize their life cycle with that of seasonal climatic changes and resources availability. However, cues for its induction are not always clear and, in some cases, a maternal effect may be involved. At the population level, just a part of the individuals may exhibit diapause with important consequences in terms of winter survival. Moreover, clear indicators of diapause state are difficult to identify. Diapause induction was thus investigated in the aphid parasitoid species Aphidius ervi Haliday (Hymenoptera: Braconidae) developing in the aphid Sitobion avenae (Hemiptera: Aphididae) at four crossed photothermal regimes (16 °C and 8 °C, 16:8 h L:D and 8:16 h L:D), and during 2 successive generations. We analyzed the reliability of changes in mummy color to assess for the diapausing state compared to dissections, and we measured parasitoid morphological and physiological traits. We observed that the proportion of dark brown mummies increased after one generation under low photothermal regime compared to other regimes. No diapause was recorded at 16 °C, 16:8 h L:D, while we observed 16.2% and 67.5% diapause incidence at 8 °C, 8:16 h L:D, at 1st and 2nd generation, respectively. Diapause induction is thus increased by short day-length conditions and low temperatures as well as by maternal effects. All parasitoid life-history traits (weight, size, fat content, water content, egg-load, and longevity) were affected by the photothermal regime and/or the generation. These results raise new questions on the environmental thresholds needed to induce diapause and on survival and adaptation potential of commercially available parasitoid strains in different environments.

Autumn larval cold tolerance does not predict the northern range limit of a widespread butterfly species

Climate change is driving range shifts, and a lack of cold tolerance is hypothesized to constrain insect range expansion at poleward latitudes. However, few, if any, studies have tested this hypothesis during autumn when organisms are subjected to sporadic low-temperature exposure but may not have become cold-tolerant yet. In this study, we integrated organismal thermal tolerance measures into species distribution models for larvae of the Giant Swallowtail butterfly, Papilio cresphontes (Lepidoptera: Papilionidae), living at the northern edge of its actively expanding range. Cold hardiness of field-collected larvae was determined using three common metrics of cold-induced physiological thresholds: the supercooling point, critical thermal minimum, and survival following cold exposure. P. cresphontes larvae were determined to be tolerant of chilling but generally die at temperatures below their SCP, suggesting they are chill-tolerant or modestly freeze-avoidant. Using this information, we examined the importance of low temperatures at a broad scale, by comparing species distribution models of P. cresphontes based only on environmental data derived from other sources to models that also included the cold tolerance parameters generated experimentally. Our modeling revealed that growing degree-days and precipitation best predicted the distribution of P. cresphontes, while the cold tolerance variables did not explain much variation in habitat suitability. As such, the modeling results were consistent with our experimental results: Low temperatures in autumn are unlikely to limit the distribution of P. cresphontes. Understanding the factors that limit species distributions is key to predicting how climate change will drive species range shifts.

Thermal performance under constant temperatures can accurately predict insect development times across naturally variable microclimates

External conditions can drive biological rates in ectotherms by directly influencing body temperatures. While estimating the temperature dependence of performance traits such as growth and development rate is feasible under controlled laboratory settings, predictions in nature are difficult. One major challenge lies in translating performance under constant conditions to fluctuating environments. Using the butterfly Pieris napi as model system, we show that development rate, an important fitness trait, can be accurately predicted in the field using models parameterized under constant laboratory temperatures. Additionally, using a factorial design, we show that accurate predictions can be made across microhabitats but critically hinge on adequate consideration of non-linearity in reaction norms, spatial heterogeneity in microclimate and temporal variation in temperature. Our empirical results are also supported by a comparison of published and simulated data. Conclusively, our combined results suggest that, discounting direct effects of temperature, insect development rates are generally unaffected by thermal fluctuations.

Rapid phenological change differs across four trophic levels over 15 years

The success of consumers often depends on synchronizing with their resources; however, recent climate change has affected the phenology of many species, resulting in mismatches and leading to community-wide changes. Field studies chronicling both the dynamics and behavior of four trophic levels seldom run for more than a few years, thereby bringing into question the longer term trajectories of these phenological shifts at multiple levels. Do these shifts between trophic levels remain constant over time, or do they continue to move apart? To address these questions, in 2004, I initiated a long-term study of the phenological relationships of two ferns, a host caterpillar (and its moth), its principal primary parasitoid wasp, and hyperparasitoid wasp. The study involves only a few species at each level, but they make up nearly all the members of the community. Ferns emerged progressively earlier in the spring, at rates exceeding one day per year, while moths eclosed roughly 0.6 days earlier per year, the primary parasitoid at 0.8 days earlier per year, and the hyperparasitoid fluctuated widely. Each of these changes fostered significant mismatches. Year-to-year changes of the moth and primary parasitoid varied much more than those of the ferns. In each instance, dates of last eclosions moved earlier more rapidly than did early eclosion dates, truncating their seasons. The extremely rapid, though variable, changes in phenology of the various trophic levels follow the unprecedentedly rapid temperature increase of the immediately adjacent Gulf of Maine.

The direct and indirect effects of extreme climate events on insects

Extreme climate events are predicted to increase in the future, which will have significant effects on insect biodiversity. Research into this area has been rapidly expanding, but knowledge gaps still exist. We conducted a review of the literature to provide a synthesis of extreme climate events on insects and identify future areas of research. In our review, we asked the following questions: 1) What are the direct and indirect mechanisms that extreme climate events affect individual insects? 2) What are the effects of extreme climate events on insect populations and demography? 3) What are the implications of the extreme climate events effects on insect communities? Drought was among the most frequently described type of extreme climate event affecting insects, as well as the effects of temperature extremes and extreme temperature variation. Our review explores the factors that determine the sensitivity or resilience to climate extremes for individuals, populations, and communities. We also identify areas of future research to better understand the role of extreme climate events on insects including effects on non-trophic interactions, alteration of population dynamics, and mediation of the functional the trait set of communities. Many insect species are under threat from global change and extreme climate events are a contributing factor. Biologists and policy makers should consider the role of extreme events in their work to mitigate the loss of biodiversity and delivery of ecosystem services by insects.

The Impact of Climate Change on Agricultural Insect Pests

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

Adaptive responses of free-living and symbiotic microalgae to simulated future ocean conditions

Marine microalgae are a diverse group of microscopic eukaryotic and prokaryotic organisms capable of photosynthesis. They are important primary producers and carbon sinks but their physiology and persistence are severely affected by global climate change. Powerful experimental evolution technologies are being used to examine the potential of microalgae to respond adaptively to current and predicted future conditions, as well as to develop resources to facilitate species conservation and restoration of ecosystem functions. This review synthesizes findings and insights from experimental evolution studies of marine microalgae in response to elevated temperature and/or pCO₂ . Adaptation to these environmental conditions has been observed in many studies of marine dinoflagellates, diatoms and coccolithophores. An enhancement in traits such as growth and photo-physiological performance and an increase in upper thermal limit have been shown to be possible, although the extent and rate of change differ between microalgal taxa. Studies employing multiple monoclonal replicates showed variation in responses among replicates and revealed the stochasticity of mutations. The work to date is already providing valuable information on species' climate sensitivity or resilience to managers and policymakers but extrapolating these insights to ecosystem- and community-level impacts continues to be a challenge. We recommend future work should include in situ experiments, diurnal and seasonal fluctuations, multiple drivers and multiple starting genotypes. Fitness trade-offs, stable versus plastic responses and the genetic bases of the changes also need investigating, and the incorporation of genome resequencing into experimental designs will be invaluable.

Genotype-environment interaction reveals varied developmental responses to unpredictable host phenology in a tropical insect

Understanding the genetic architecture of life history plasticity may inform resilience under environmental change, but relatively little is known for the inhabitants of unpredictable wet-dry tropical environments. Here, I explore the quantitative genetics of juvenile growth and development relative to hostplant phenology in the butterfly Eurema hecabe. Wet season generations of this species breed explosively on leguminous annuals whereas dry season generations subsist at low density upon an alternative perennial host. The wet-to-dry season transition is temporally unpredictable and marked by widespread host defoliation, forcing a large cohort of stranded larvae to either pupate prematurely or prolong development in the hope of renewed foliage production. A split-brood experiment demonstrated greater performance on high quality annual as opposed to perennial host foliage and a marked decline under the stressed conditions faced by stranded wet season larvae. Genetic variances for rates of growth and development were equivalent among high quality treatments but strikingly elevated under resource stress, and the associated cross-environment genetic correlations were indistinguishable from zero. The results demonstrate genotype-environment interaction involving both rank order and variance scale, thereby revealing genetic variance for norms of reaction that may reflect variable risk aversion given an unpredictable tropical host phenology.

Community-wide seasonal shifts in thermal tolerances of mosquitoes

The broadening in species' thermal tolerance limits and breadth from tropical to temperate latitudes is proposed to reflect spatial gradients in temperature seasonality, but the importance of seasonal shifts in thermal tolerances within and across locations is much less appreciated. We performed thermal assays to examine the maximum and minimum critical temperatures (CT_max and CT_min , respectively) of a mosquito community across their active seasons. Mosquito CT_min tracked seasonal shifts in temperature, whereas CT_max tracked a countergradient pattern with lowest heat tolerances in summer. Mosquito thermal breadth decreased from spring to summer and then increased from summer to autumn. We show a temporal dichotomy in thermal tolerances with thermal breadths of temperate organisms in summer reflecting those of the tropics ("tropicalization") that is sandwiched between a spring and autumn "temperatization." Therefore, our tolerance patterns at a single temperate latitude recapitulate classical patterns across latitude. These findings highlight the need to understand the temporal and spatial components of thermotolerance variation better, including plasticity and rapid seasonal selection, and the potential for this variation to affect species responses to climate change. With summers becoming longer and increasing winter nighttime temperatures, we expect increasing tropicalization of species thermal tolerances in both space and time.

Geographic variation in acclimation responses of thermal tolerance in South African diving beetles (Dytiscidae: Coleoptera)

Understanding sources of variation in animal thermal limits is critical to forecasting ecological responses to climate change. Here, we estimated upper and lower thermal limits, and their capacity to respond to thermal acclimation, in several species and populations of diving beetles (Dytiscidae) from diverse geographic regions representative of variable climate within South Africa. We also considered ecoregions and latitudinal ranges as potential predictors of thermal limits and the plasticity thereof. For upper thermal limits, species showed significant variation and limited acclimation-related plasticity. Lower thermal limits responded to acclimation in some cases and showed marked variation among species that could be explained by taxonomic affiliation and ecoregion. Limited acclimation ability in the species included in this study suggest plasticity of thermal limits will not be a likely buffer for coping with climate change. From the present results for the Dytiscidae of the region, it appears the group may be particularly susceptible to heat and/or drought and may thus serve as useful indicator species of ecosystem change. Understanding how these climate-related impacts play out at different spatial and temporal scales will have profound implications for conservation management and functional responses, especially important in a region already showing a trend for warming and drying.

Are extreme high temperatures at low or high latitudes more likely to inhibit the population growth of a globally distributed aphid?

Although climate warming can increase both mean temperature and its variability, it is often the effects of climate warming on short periods of extreme temperatures that are expected to have particularly large physiological and ecological consequences. Understanding the vulnerability of organisms at various latitudes to climate extremes is thus critical for understanding warming effects on regional biodiversity conservation and ecosystem management. While previous studies have shown that thermal responses depend on temperature regimes that organisms have previously experienced, this issue has not been considered much when comparing the effects of temperature extremes at different latitudes. To fill this gap, here we manipulated different combinations of amplitude and duration of daily high temperature extremes to simulate conditions at different latitudes. We tested the effects of those regimes on life-history traits and fitness of a globally-distributed aphid species, Rhopalosiphum padi. We compared our results with previous studies to better understand the extent to which these regimes affect conclusions based on comparisons under different mean temperatures. As a consequence of asymmetrical thermal performance curves, we hypothesized that the temperature regimes with higher daily maximum temperatures at higher latitudes would cause strong negative effects. Our results showed that these regimes with thermal extremes caused substantial decreases in life-history traits and fitness relative to the predictions from different mean temperatures. Specifically, the regime with higher daily maximum temperature reflecting a higher mid-latitude location had larger impacts on development, reproduction and population fitness than the regime representing a lower mid-latitude location. These findings have implications for understanding the vulnerability of organisms across latitudes to increasingly frequent extreme heat events under ongoing climate warming.

When it's hot and dry: life-history strategy influences the effects of heat waves and water limitation

The frequency, duration and co-occurrence of several environmental stressors, such as heat waves and droughts, are increasing globally. Such multiple stressors may have compounding or interactive effects on animals, resulting in either additive or non-additive costs, but animals may mitigate these costs through various strategies of resource conservation or shifts in resource allocation. Through a factorial experiment, we investigated the independent and interactive effects of a simulated heat wave and water limitation on life-history, physiological and behavioral traits. We used the variable field cricket, Gryllus lineaticeps, which exhibits a wing dimorphism that mediates two distinct life-history strategies during early adulthood. Long-winged individuals invest in flight musculature and are typically flight capable, whereas short-winged individuals lack flight musculature and capacity. A comprehensive and integrative approach with G. lineaticeps allowed us to examine whether life-history strategy influenced the costs of multiple stressors as well as the resulting cost-limiting strategies. Concurrent heat wave and water limitation resulted in largely non-additive and single-stressor costs to important traits (e.g. survival and water balance), extensive shifts in resource allocation priorities (e.g. reduced prioritization of body mass) and a limited capacity to conserve resources (e.g. heat wave reduced energy use only when water was available). Life-history strategy influenced the emergency life-history stage because wing morphology and stressor(s) interacted to influence body mass, boldness behavior and immunocompetence. Our results demonstrate that water availability and life-history strategy should be incorporated into future studies integrating important conceptual frameworks of stress across a suite of traits - from survival and life history to behavior and physiology.

Time course of acclimation of critical thermal limits in two springtail species (Collembola)

Critical thermal limits are one of the most important sources of information on the possible impacts of climate change on soil microarthropods. The extent of plasticity of tolerance limits can provide valuable insights about the likely responses of ectotherms to environmental change. Although many studies have investigated various aspects of the acclimatory response of thermal limits to temperature changes in arthropods, the number of studies focusing on the temporal dynamics of this plastic response is relatively small. Collembola, one of the key microarthropods groups in almost all soil ecosystems around the world, have been the focus of several thermal acclimation studies. Yet the time course of acclimation and its reversal have not been widely studied in this group. Here we investigated the time course of acclimation of critical thermal maxima (CT_max) and minima (CT_min) of two springtail species. We exposed a Cryptopygus species from temperate southern Australia to high and low temperature conditions and Mucrosomia caeca from Sub-Antarctic Macquarie Island to high temperature conditions. Upper thermal limits in both species were found to be highly constrained, as CT_max did not show substantial response to high and low temperature acclimation both in the Cryptopygus species and M. caeca, whereas CT_min showed significant responses to high and low temperature conditions. The acclimation begins to stabilize in approximately seven days in all treatments except for the acclimation of CT_min under high temperature conditions, where the pattern of change suggests that this acclimation might take longer to be completed. Although reversal of this acclimation also begins to stabilize under 7 days, re-acclimation was relatively slow as we did not observe a very clear settling point in 2 of the 3 re-acclimation treatments. The observed limits on the plasticity of CT_max indicate that both of these species may be very limited in their ability to respond plastically to short-term rapid changes in temperature (i.e temperature extremes).

Disease Vector Relative Spatio-Temporal Abundances to Water Bodies and Thermal Fitness Across Malaria Endemic Semi-Arid Areas

The biophysical environment plays an important role in the spatio-temporal abundance and distribution of mosquitoes. This has implications for the spread of vectors and diseases they cause across diverse landscapes. Here, we assessed vector mosquito abundances in relation to large water bodies, from three malaria districts in a semi-arid environment. Furthermore, we explored thermal limits to activity of the dominant and most medically important malaria vector across malaria-endemic areas. Mosquitoes were trapped near permanent water bodies across different districts. Critical thermal limits (critical thermal-maxima and -minima) to activity of wild adults and 4th instar larvae Anopheles arabiensis (Diptera: Culicidae) were assessed. Our results showed that Anopheles spp. dominate mosquito communities across all three districts, but that their numbers were far greater in Okavango than in other regions. At the Okavango sites, the numbers of Anopheles spp. decreased with distance from main water source. Anopheles spp. sampled in this region comprised Anopheles gambiae (Giles,1902) and Anopheles funestus (Giles, 1900) species complexes, with the former dominating in numbers. Thermal activity assays showed An. arabiensis females had wider thermal tolerance windows than males while larval thermal activity limits differed significantly across space. These results confirm that the Okavango district should be prioritized for vector control measures. Moreover, intervention strategies should consider recommendations for proximity effects to large water bodies, given the differential risk associated with distance from water. The wider thermal window on female vectors has implications for possible future malaria transmission and diverse habitat utilization under changing environments.

Climate vulnerability of South American freshwater fish: Thermal tolerance and acclimation

Freshwater fish are restricted by their physiology to rivers and lakes, and are generally limited in their capacity to disperse across basins. As a result, there is often a close match between the evolutionary history of river basins and their natural history. Thus, the regional landscape and ecological features, such as temperature, have shaped the evolution and adaptation of local fish assemblages. Climate change is expected to affect fish diversity and increase extinction, especially in low latitudes, and it has been suggested that species that inhabit low latitude species are more susceptible since they live close to their maximum thermal limits and have low capacity for acclimation. To understand the mechanisms of variation in thermal tolerance across a broad-scale of South American fishes is fundamental to be able to assess the vulnerability of species and habitat to global warming. Herein, we present the first attempt to analyze the vulnerability of South American freshwater fish species, based on the review of upper thermal limits of 106 species from a broad range of latitudinal habitats. Our findings show that upper thermal limits decrease with latitude, while the thermal safety margin (TSM) increase. Furthermore, the latitude has little effects on the acclimation response ratio, and the TSM decreased with rising temperatures. These data suggest that thermal phenotypic acclimation has low potential for mitigating global warming. These results indicate that South American fish species living in tropical areas are more susceptible to global warming since they are already living close to their maximum habitat temperature.

Shifts in the relative fitness contributions of fecundity and survival in variable and changing environments

Organisms respond to shifts in climate means and variability via distinct mechanisms. Accounting for these differential responses and appropriately aggregating them is central to understanding and predicting responses to climate variability and change. Separately considering fitness components can clarify organismal responses: fecundity is primarily an integrated, additive response to chronic environmental conditions over time via mechanisms such as energy use and acquisition, whereas survival can be strongly influenced by short-term, extreme environmental conditions. In many systems, the relative importance of fecundity and survival constraints changes systematically along climate gradients, with fecundity constraints dominating at high latitudes or altitudes (i.e. leading range edges as climate warms), and survival constraints dominating at trailing range edges. Incorporating these systematic differences in models may improve predictions of responses to recent climate change over models that assume similar processes along environmental gradients. We explore how detecting and predicting shifts in fitness constraints can improve our ability to forecast responses to climate gradients and change.

Dealing with predictable and unpredictable temperatures in a climate change context: the case of parasitoids and their hosts

The Earth's climate is changing at a rapid pace. To survive in increasingly fluctuating and unpredictable environments, species can either migrate or evolve through rapid local adaptation, plasticity and/or bet-hedging. For small ectotherm insects, like parasitoids and their hosts, phenotypic plasticity and bet-hedging could be critical strategies for population and species persistence in response to immediate, intense and unpredictable temperature changes. Here, we focus on studies evaluating phenotypic responses to variable predictable thermal conditions (for which phenotypic plasticity is favoured) and unpredictable thermal environments (for which bet-hedging is favoured), both within and between host and parasitoid generations. We then address the effects of fluctuating temperatures on host-parasitoid interactions, potential cascading effects on the food web, as well as biological control services. We conclude our review by proposing a road map for designing experiments to assess if plasticity and bet-hedging can be adaptive strategies, and to disentangle how fluctuating temperatures can affect the evolution of these two strategies in parasitoids and their hosts.

Physiological adaptation to cities as a proxy to forecast global-scale responses to climate change

Cities are emerging as a new venue to overcome the challenges of obtaining data on compensatory responses to climatic warming through phenotypic plasticity and evolutionary change. In this Review, we highlight how cities can be used to explore physiological trait responses to experimental warming, and also how cities can be used as human-made space-for-time substitutions. We assessed the current literature and found evidence for significant plasticity and evolution in thermal tolerance trait responses to urban heat islands. For those studies that reported both plastic and evolved components of thermal tolerance, we found evidence that both mechanisms contributed to phenotypic shifts in thermal tolerance, rather than plastic responses precluding or limiting evolved responses. Interestingly though, for a broader range of studies, we found that the magnitude of evolved shifts in thermal tolerance was not significantly different from the magnitude of shift in those studies that only reported phenotypic results, which could be a product of evolution, plasticity, or both. Regardless, the magnitude of shifts in urban thermal tolerance phenotypes was comparable to more traditional space-for-time substitutions across latitudinal and altitudinal clines in environmental temperature. We conclude by considering how urban-derived estimates of plasticity and evolution of thermal tolerance traits can be used to improve forecasting methods, including macrophysiological models and species distribution modelling approaches. Finally, we consider areas for further exploration including sub-lethal performance traits and thermal performance curves, assessing the adaptive nature of trait shifts, and taking full advantage of the environmental thermal variation that cities generate.

The thermal environment at fertilization mediates adaptive potential in the sea

Additive genetic variation for fitness at vulnerable life stages governs the adaptive potential of populations facing stressful conditions under climate change, and can depend on current conditions as well as those experienced by past stages or generations. For sexual populations, fertilization is the key stage that links one generation to the next, yet the effects of fertilization environment on the adaptive potential at the vulnerable stages that then unfold during development are rarely considered, despite climatic stress posing risks for gamete function and fertility in many taxa and external fertilizers especially. Here, we develop a simple fitness landscape model exploring the effects of environmental stress at fertilization and development on the adaptive potential in early life. We then test our model with a quantitative genetic breeding design exposing family groups of a marine external fertilizer, the tubeworm Galeolaria caespitosa, to a factorial manipulation of current and projected temperatures at fertilization and development. We find that adaptive potential in early life is substantially reduced, to the point of being no longer detectable, by genotype‐specific carryover effects of fertilization under projected warming. We interpret these results in light of our fitness landscape model, and argue that the thermal environment at fertilization deserves more attention than it currently receives when forecasting the adaptive potential of populations confronting climate change.

Does local adaptation along a latitudinal cline shape plastic responses to combined thermal and nutritional stress?

Thermal and nutritional stress are commonly experienced by animals. This will become increasingly so with climate change. Whether populations can plastically respond to such changes will determine their survival. Plasticity can vary among populations depending on the extent of environmental heterogeneity. However, theory conflicts as to whether environmental heterogeneity should increase or decrease plasticity. Using three locally adapted populations of Drosophila melanogaster sampled from a latitudinal gradient, we investigated whether plastic responses to combinations of nutrition and temperature increase or decrease with latitude for four traits: egg-adult viability, egg-adult development time, and two body size traits. Employing nutritional geometry, we reared larvae on 25 diets varying in protein and carbohydrate content at two temperatures: 18 and 25°C. Plasticity varied among traits and across the three populations. Viability was highly canalized in all three populations. The tropical population showed the least plasticity for development time, the sub-tropical showed the highest plasticity for wing area, and the temperate population showed the highest plasticity for femur length. We found no evidence of latitudinal plasticity gradients in either direction. Our data highlight that differences in thermal variation and resource predictability experienced by populations along a latitudinal cline are not sufficient to predict their plasticity.

N-acetyltyrosine-induced redox signaling in hormesis

A suite of adaptations allows insects to survive in hostile terrestrial environments for long periods of time. Temperature represents a key environmental factor for most ectothermic insects, and they rapidly acclimate to high and low temperatures. Vast amounts of data in this research field support the idea that an insect's ability to tolerate fluctuating temperatures can be regarded as a biphasic hormetic dose response. Observation indicates that their thermal hormetic response represents a conservative estimate of their intrinsic capacity for rapid adaptation to environmental changes in nature because they naturally experience diel or seasonal temperature fluctuations. It is therefore reasonable to suppose that the hormetic response in insects reflects a surplus physiological capacity to deal with temperature changes that they would experience naturally. Although it has been unknown how thermal acclimation is induced, a stress-dependent increase in N-acetyltyrosine (NAT) was recently found to occur in insect larvae who had endured high temperatures. NAT treatment was demonstrated to induce thermotolerance in several tested insect species. NAT was also identified in the serum of humans as well as mice, and its concentration in mice was shown to be increased by heat and restraint stress, with NAT pretreatment lowering the concentrations of corticosterone and peroxidized lipids in stressed mice. These recent findings may give us some hints about how long a hormetic response lasts. Here, I will discuss recent findings underlying hormetic responses induced by an intrinsic factor, NAT, and how the hormetic response may begin and end.

Drought-induced reduction in flower size and abundance correlates with reduced flower visits by bumble bees

Reduced water availability can cause physiological stress in plants that affects floral development leading to changes in floral morphology and traits that mediate interactions with pollinators. As pollinators can detect small changes in trait expressions, drought-induced changes in floral traits could affect pollinator visitations. However, the linkage between changes in floral traits and pollinator visitations under drought conditions is not well explored. We, therefore, tested whether drought-induced changes in floral morphology and abundance of flowers are linked to changes in pollinator visitations. We conducted flight cage experiments with a radio frequency identification system for automated visitation recordings with bumble bees (Bombus terrestris) and common charlock (Sinapis arvensis) as the model system. In total, we recorded interactions for 31 foraging bumble bees and 6569 flower visitations. We found that decreasing soil moisture content correlated with decreasing size of all measured morphological traits except stamen length and nectar tube width. The reductions in floral size, petal width and length, nectar tube depth and number of flowers resulted in decreasing visitation rates by bumble bees. These decreasing visitations under lower soil moisture availability might be explained by lower numbers of flowers and thus a reduced attractiveness and/or by increased difficulties experienced by bumble bees in handling smaller flowers. Whether these effects act additively or synergistically on pollinator behaviour and whether this leads to changes in pollen transfer and to different selectionp ressures require further investigation.

The dynamics of the development of harmful insects on the mother planting of basic grape plants in the Rostov region

The study results on prevalence of the main harmful insects on the mother planting of the basic grape plants of the Rostov region: rose leafhopper, buffalo treehopper, tree cricket, tobacco and grape thrips, which are polyphagous phytophages, are presented. As a result of the negative impact of harmful organisms the plant normal development is disrupted. The spread and increase in the insect harmfulness in the Rostov region is facilitated by an increase in the average annual temperature to 9.5-11.6 °C in the last 10-15 years, which is the lower limit for their survival. A close direct relationship was revealed between the average annual temperature and the leafhopper and thrip harmfulness: r=0.72-0.89 and an unobvious dependence of the tree cricket harmfulness on thermal conditions (r=0.59). The phytosanitary control system in the mother planting made it possible to restrain the harmful organism development, with a harmfulness not exceeding 1.3 points for thrips and 2 points for other insects for further reproduction of practically healthy grape planting material while maintaining the status basic plants.

A region of the sex chromosome associated with population differences in diapause induction contains highly divergent alleles at clock genes

Developmental plasticity describes the capacity of individuals with the same genotype to induce permanent change in a phenotype depending on a specific external input. One well‐studied example of adaptive developmental plasticity is the induction of facultative diapause in insects. Studies investigating the inheritance of diapause induction have suggested diverse genetic origins. However, only few studies have performed genome‐wide scans to identify genes affecting the induction decision. Here we compare two populations of the butterfly Pieris napi that differ in the propensity to enter diapause, and despite showing a low genome‐wide divergence, we identify a few genomic regions that show high divergence between populations. We then identified a single genomic region associated with diapause induction by genotyping diapausing and directly developing siblings from backcrosses of these populations. This region is located on the Z chromosome and contained three circadian clock genes, cycle, clock, and period. Additionally, period harbored the largest number of SNPs showing complete fixation between populations. We conclude that the heritable basis of between‐population variation in the plasticity that determines diapause induction resides on the Z chromosome, with the period gene being the prime candidate for the genetic basis of adaptive plasticity.

Multidimensional plasticity in the Glanville fritillary butterfly: larval performance is temperature, host and family specific

Variation in environmental conditions during development can lead to changes in life-history traits with long-lasting effects. Here, we study how variation in temperature and host plant (i.e. the consequences of potential maternal oviposition choices) affects a suite of life-history traits in pre-diapause larvae of the Glanville fritillary butterfly. We focus on offspring survival, larval growth rates and relative fat reserves, and pay specific attention to intraspecific variation in the responses (G × E × E). Globally, thermal performance and survival curves varied between diets of two host plants, suggesting that host modifies the temperature impact, or vice versa. Additionally, we show that the relative fat content has a host-dependent, discontinuous response to developmental temperature. This implies that a potential switch in resource allocation, from more investment in growth at lower temperatures to storage at higher temperatures, is dependent on the larval diet. Interestingly, a large proportion of the variance in larval performance is explained by differences among families, or interactions with this variable. Finally, we demonstrate that these family-specific responses to the host plant remain largely consistent across thermal environments. Together, the results of our study underscore the importance of paying attention to intraspecific trait variation in the field of evolutionary ecology.

Climate stress resistance in male Queensland fruit fly varies among populations of diverse geographic origins and changes during domestication

Background

The highly polyphagous Queensland fruit fly (Bactrocera tryoni Froggatt) expanded its range substantially during the twentieth century and is now the most economically important insect pest of Australian horticulture, prompting intensive efforts to develop a Sterile Insect Technique (SIT) control program. Using a “common garden” approach, we have screened for natural genetic variation in key environmental fitness traits among populations from across the geographic range of this species and monitored changes in those traits induced during domestication.

Results

Significant variation was detected between the populations for heat, desiccation and starvation resistance and wing length (as a measure of body size). Desiccation resistance was correlated with both starvation resistance and wing length. Bioassay data for three resampled populations indicate that much of the variation in desiccation resistance reflects persistent, inherited differences among the populations. No latitudinal cline was detected for any of the traits and only weak correlations were found with climatic variables for heat resistance and wing length. All three stress resistance phenotypes and wing length changed significantly in certain populations with ongoing domestication but there was also a strong population by domestication interaction effect for each trait.

Conclusions

Ecotypic variation in heat, starvation and desiccation resistance was detected in Australian Qfly populations, and these stress resistances diminished rapidly during domestication. Our results indicate a need to select source populations for SIT strains which have relatively high climatic stress resistance and to minimise loss of that resistance during domestication.