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

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

Genetic differentiation and adaptive evolution of buff-tailed bumblebees in Asia

Bumblebees are important pollinating insects, so their declines resulting from environmental change have received intensive attention. Understanding how environmental factors shape the genetic structure of natural populations and identifying the genetic basis of local adaptation will provide insights into how bumblebees cope with environmental change. The buff-tailed bumblebee (Bombus terrestris) has a wide natural distribution range and has been domesticated to produce commercial colonies for greenhouse pollination. Previous population genetics studies on B. terrestris have mainly focused on its European populations; however, its Asian populations, representing the eastern side of its natural distribution, remain largely unsampled. To fill this gap, we collected wild B. terrestris samples from Asia, as well as wild B. terrestris samples from Europe and samples from domesticated colonies. We conducted whole-genome resequencing for 77 collected B. terrestris and performed population genomics analysis. Our results indicate that distinct genetic differentiation (FST = 0.076) exists between B. terrestris in Europe and Asia, with substantial morphological and physiological differences detected between them; B. terrestris in Asia should represent a distinct genetic resource. Demographic analysis suggests that the effective population size of B. terrestris has increased during historic cold periods, indicating their cold-adapted characteristics. Selective sweep analysis identified 331 genes under selection in the genomes of Asian B. terrestris, likely involved in their adaptation to the high ultraviolet radiation, low temperature and low precipitation of their habitats. Our research provides insights into the population genetic structure and genetic basis of local adaptation in the buff-tailed bumblebee, which will be useful for its conservation and management.

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

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

Integrating multiple evidence streams to understand insect biodiversity change

Insects dominate animal species diversity yet face many threats from anthropogenic drivers of change. Many features of insect ecology make them a challenging group, and the fragmented state of knowledge compromises our ability to make general statements about their status. In this Review, we discuss the challenges of assessing insect biodiversity change. We describe how multiple lines of evidence-time series, spatial comparisons, experiments, and expert opinion-can be integrated to provide a synthesis overview of how insect biodiversity responds to drivers. Applying this approach will generate testable predictions of insect biodiversity across space, time, and changing drivers. Given the urgency of accelerating human impacts across the environment, this approach could yield a much-needed rapid assessment of insect biodiversity change.

Insect immunity in the Anthropocene

Anthropogenic activities result in global change, including climate change, landscape degradation and pollution, that can alter insect physiology and immune defences. These changes may have contributed to global insect decline and the dynamics of insect-transmitted diseases. The ability of insects to mount immune responses upon infection is crucial for defence against pathogens and parasites. Suppressed immune defences reduce fitness by causing disease-driven mortality and elevated immune responses reduce energy available to invest in other fitness traits such as reproduction. Understanding the impact of anthropogenic factors on insect-pathogen interactions is therefore key to determining the contribution of anthropogenic global change to pathogen-driven global insect decline and the emergence and transmission of insect-borne diseases. Here, we synthesise evidence of the impact of anthropogenic factors on insect immunity. We found evidence that anthropogenic factors, such as insecticides and heavy metals, directly impacting insect immune responses by inhibiting immune activation pathways. Alternatively, factors such as global warming, heatwaves, elevated CO2 and landscape degradation can indirectly reduce insect immune responses via reducing the energy available for immune function. We further review how anthropogenic factors impact pathogen clearance and contribute to an increase in vector-borne diseases. We discuss the fitness cost of anthropogenic factors via pathogen-driven mortality and reduced reproductive output and how this can contribute to species extinction. We found that most research has determined the impact of a single anthropogenic factor on insect immune responses or pathogen resistance. We recommend studying the combined impact of multiple stressors on immune response and pathogen resistance to understand better how anthropogenic factors affect insect immunity. We conclude by highlighting the importance of initiatives to mitigate the impact of anthropogenic factors on insect immunity, to reduce the spread of vector-borne diseases, and to protect vulnerable ecosystems from emerging diseases.

Leaf-damaging behavior by queens is widespread among bumblebee species

Phenological mismatches and resource limitations resulting from ongoing environmental change can have severe impacts on pollinator fitness. Recent findings show that bumblebee workers respond to pollen scarcity by damaging plant leaves in ways that can accelerate flowering, suggesting a mechanism by which direct information transfer from bees to plants might influence the timing of flower production. However, the ecological and adaptive significance of this interaction remains uncertain. Here we report that mated and unmated queens of Bombus terrestris also damage leaves, with similar effects on flowering. Furthermore, we document leaf damage by wild-caught queens from 12 species, spanning seven subgenera, indicating damaging behavior is widespread among Bombus species. Leaf damage by bumblebee queens may have particular relevance in the context of colony founding and early development, where the timely availability of local floral resources can be critical for colony success and fitness.

Forecasting the Impact of Climate Change on Apis dorsata (Fabricius, 1793) Habitat and Distribution in Pakistan

Climate change has led to global biodiversity loss, severely impacting all species, including essential pollinators like bees, which are highly sensitive to environmental changes. Like other bee species, A. dorsata is also not immune to climate change. This study evaluated the habitat suitability of A. dorsata under climate change in Pakistan by utilizing two years of occurrence and distribution data to develop a Maximum Entropy (MaxEnt) model for forecasting current and future habitat distribution. Future habitat projections for 2050 and 2070 were based on two shared socioeconomic pathways (SSP245 and SSP585) using the CNRM-CM6-1 and EPI-ESM1-2-HR-1 global circulation models. Eight bioclimatic variables (Bio1, Bio4, Bio5, Bio8, Bio10, Bio12, Bio18, and Bio19) were selected for modeling, and among the selected variables, the mean temperature of the wettest quarter (Bio8) and precipitation of the warmest quarter (Bio18) showed major contributions to the model building and strongest influence on habitat of A. dorsata. The model estimated 23% of our study area as a suitable habitat for A. dorsata under current climatic conditions, comprising 150,975 km2 of moderately suitable and 49,792 km2 of highly suitable regions. For future climatic scenarios, our model projected significant habitat loss for A. dorsata with a shrinkage and shift towards northern, higher-altitude regions, particularly in Khyber Pakhtunkhwa and the Himalayan foothills. Habitat projections under the extreme climatic scenario (SSP585) are particularly alarming, indicating a substantial loss of the suitable habitat for the A. dorsata of 40% under CNRM-CM6-1 and 79% for EPI-ESM1-2-HR-1 for the 2070 time period. This study emphasizes the critical need for conservation efforts to protect A. dorsata and highlights the species' role in pollination and supporting the apiculture industry in Pakistan.

An in-depth dataset of northwestern European arthropod life histories and ecological traits

Background

In response to the ongoing biodiversity crisis amongst arthropods, it is essential to implement efficient conservation strategies to safeguard both species diversity and the vital ecosystem services they provide. Developing such strategies requires reliable predictive models that can identify the species that are the most vulnerable to current and future threats, including those posed by climate and land-use change. Species life histories are central to these models, as they influence both population dynamics and spread rates.

New information

To support this effort, we compiled a dataset with key traits for arthropods based on several literature sources and expert knowledge. The dataset contains data on body size, life history, thermal niche and ecology for 4874 northwestern European species across 10 different orders. By gathering these essential trait data, we aim to create a robust foundation for predicting species vulnerability and anticipating shifts in arthropod communities in response to global change.

Exploring climate-related gut microbiome variation in bumble bees: An experimental and observational perspective

Rising temperatures negatively affect bumble bee fitness directly through physiological impacts and indirectly by disrupting mutualistic interactions between bees and other organisms, which are crucial in determining species-specific responses to climate change. Gut microbial symbionts, key regulators of host nutrition and health, may be the Achilles' heel of thermal responses in insects. They not only modulate biotic interactions with plants and pathogens but also exhibit varying thermal sensitivity themselves. Understanding how environmental changes disrupt microbiome communities is a crucial first step to determine potential consequences for host population responses. We analyzed gut bacterial communities of six bumble bee species inhabiting different climatic niches along an elevational gradient in the German Alps using 16S ribosomal DNA amplicon sequencing. We first investigated whether inter- and intraspecific differences in gut bacterial communities can be linked to species' elevational niches, which differ in temperature, flower resource composition, and likely pathogen pressure. A reciprocal translocation experiment between distinct climatic regions tested how the gut bacterial communities of Bombus terrestris and Bombus lucorum change short-term when exposed to new environments. Finally, we exposed these species to heat and cold wave scenarios within climate chambers to disentangle pure temperature-driven effects on the microbiome from other environmental effects. Interspecific variation in microbiome composition exceeded intraspecific variation. Species exhibit varying levels of gut microbiome stability, where stability is defined as the within-group variance: lower stability, indicated by greater within-group variance, is predominantly observed in species inhabiting higher elevations. Transplanted species showed subtle short-term gut microbiome adjustments, marked by an increase in Lactobacillaceae upon exposure to warmer regions; however, the gut microbiomes of these bumble bees did not change under laboratory temperature scenarios. We conclude that marked differences in the gut microbiomes of bumble bees could lead to species-specific responses to environmental change. For example, less stable microbiomes in bumble bees inhabiting higher elevations might indicate an increased sensitivity to pathogens. Short-term microbiome changes following translocation indicate that species with relatively stable microbiomes, such as B. lucorum and B. terrestris, can rapidly integrate new bacteria, which could increase their capacity to cope with new environments under climate change.

Integrating data to assess occupancy patterns of an endangered bumble bee

There is growing interest in integrating community science data with structured monitoring data to estimate changes in distribution patterns of imperiled species, including pollinators. However, significant challenges remain in determining how unstructured community science data should be incorporated into formal analyses of species distributions. We developed a dynamic framework for combining community science and structured monitoring data of bumble bees to estimate changes in occupancy of rusty-patched bumble bees (Bombus affinis), a federally endangered species in the United States. We applied traditional metapopulation theory and accounted for imperfect detection to estimate site-specific extirpation risk and colonization rates across the known distribution of B. affinis in the Upper Midwest (USA). Despite a 144% increase in presence-only detections from 2017 to 2022, occupancy probabilities and the estimated number of occupied sites remained static or declined slightly across a 4-state region during this period. Our results provide preliminary evidence that the probability of local extirpation risk of B. affinis increased in response to drought, but that effect was tempered with a high number of neighboring patches occupied by B. affinis (i.e., rescue effect). Our framework can be used by managers to track population recovery goals for B. affinis and other bumble bees of conservation concern. In addition, our study highlights the importance of accounting for imperfect detection and addressing spatial sampling biases in bumble bee monitoring efforts, particularly those for which a portion of the monitoring data are generated from community science projects.

The host phylogeny and climate determine the gut bacteria of global insects

Insects play an indispensable role in ecosystems; however, in recent years, the rapid decline in global insect diversity and abundance has posed a significant threat to our survival environment. Insect gut microbes play a crucial role in the survival of insects. Understanding their global traits will be advantageous for insect protection, thus safeguarding our environment. In this study, 11,814 samples of 334 insect species from global public databases were analyzed. We found that host phylogeny and climate were decisive factors in shaping the structure of insect gut bacteria. We also identified 168 core gut bacteria of insects, more than half of which were correlated with temperatures during the coldest and wettest periods or temperature fluctuations. Moreover, machine learning predictions showed that future climate warming will lead to a decrease in alpha diversity and core bacteria of insects. Together, our study indicated that insect gut bacteria were closely related to the host, and climate warming may harm the gut bacteria, leading to a decline in insect species and populations worldwide.

Biodiversity of Bees (Hymenoptera: Apoidea: Anthophila) in Connecticut (USA)

In response to calls for national and regional updated inventories of bee species, we present a county-level checklist for 385 confirmed bee (Apoidea: Anthophila) species for Connecticut, USA, highlighting rare and regionally declining species, species that have specific habitat and/or host requirements, and species whose taxonomy and distribution we wish to clarify. We have compiled a comprehensive, digitized database of historic and current bee records from Connecticut to inform this checklist, which includes specimen records from museums, recent collections, and community science observations from iNaturalist.com. All images of bees from Connecticut on iNaturalist (18,471 observations) have been fully vetted by one or more of the authors, which is unprecedented for a state project. We summarize historical bee research in Connecticut and provide current information regarding the distribution of bee species, changes in status, phenology, habitat usage, and floral associations within the state. At least 43 of 385 species represented in collections or literature have not been detected in Connecticut since the year 2000. These and other species of conservation concern are discussed with reference to a quantitative assessment of changes in range within the state. In addition, we have calculated and report state-level ranks for 124 bee species in Connecticut. We corroborate regional loss of species including Coelioxys funerarius Smith and Holcopasites illinoiensis (Robertson) and clarify and extend the distribution of numerous bee species in the Northeastern United States. Furthermore, we discuss morphospecies, excluded species, and species expected for Connecticut. We also validate synonymies reported previously online based on an unpublished manuscript by Roy Snelling for the following species: Nomada depressa Cresson (= N. hoodiana Cockerell; = N. carinicauda Cockerell; = N. media Mitchell); Nomada obliterata Cresson (= N. decepta Mitchell); Nomada vicina Cresson (= N. beulahensis Cockerell; = N. vicina stevensi Swenk). In addition, we recognize three new synonyms of Nomada xanthura Cockerell (= N. ochlerata Mitchell; = N. detrita Mitchell; = N. mendica Mitchell) and report the first Nomada townesi Mitchell from outside of Maryland. In addition to N. townesi, the following eleven native species are newly reported or recently confirmed for Connecticut: Andrena (Cnemidandrena) parnassi----ae Cockerell; Andrena (Melandrena) sayi Robertson; Andrena (Trachandrena) rehni Viereck; Anthophora bomboides Kirby; Nomada armatella Cockerell; Nomada electella Cockerell; Nomada placida Cresson; Lasioglossum (Dialictus) cattellae (Ellis); Lasioglossum (Dialictus) ellisiae (Sandhouse); Lasioglossum (Dialictus) fattigi (Mitchell); Lasioglossum (Dialictus) trigeminum Gibbs. The following recent arrivals among non-native species are confirmed: Pseudoanthidium (Pseudoanthidium) nanum (Mocsáry); Coelioxys (Allocoelioxys) coturnix Pérez; Osmia (Osmia) taurus Smith. This work is a stepping stone towards a larger, ongoing effort to clarify bee distribution and status in New England. As such, we also report updates for the bee fauna of the following states: Massachusetts-Melissodes communis communis Cresson; Megachile (Eutricharaea) apicalis Spinola), Maine-Chelostoma philadelphi (Robertson), and New Hampshire-Lasioglossum nelumbonis (Robertson).

Leveraging Transcriptional Signatures of Diverse Stressors for Bumble Bee Conservation

Organisms in nature are subjected to a variety of stressors, often simultaneously. Foremost among stressors of key pollinators are pathogens, poor nutrition and climate change. Landscape transcriptomics can be used to decipher the relative role of stressors, provided there are unique signatures of stress that can be reliably detected in field specimens. In this study, we identify biomarkers of bumble bee (Bombus impatiens) responses to key stressors by first subjecting bees to various short-term stressors (cold, heat, nutrition and pathogen challenge) in a laboratory setting and assessing their transcriptome responses. Using random forest classification on this whole transcriptome data, we were able to discriminate each stressor. Our best model (tissue-specific model trained on a subset of important genes) correctly predicted known stressors with 92% accuracy. We then applied this random forest model to wild-caught bumble bees sampled across a heatwave event at two sites in central Pennsylvania, US, expected to differ in baseline temperature and floral resource availability. Transcriptomes of bees sampled during the heat wave's peak showed signatures of heat stress, while bees collected in the relatively cooler morning periods showed signatures of starvation and cold stress. We failed to pick up on signals of heat stress shortly after the heatwave, suggesting this set of biomarkers is more useful for identifying acute stressors than long-term monitoring of chronic, landscape-level stressors. We highlight future directions to fine-tune landscape transcriptomics towards the development of better stress biomarkers that can be used both for conservation and improving understanding of stressor impacts on bees.

The Role of Pathogens in Bumblebee Decline: A Review

Bumblebees, the most important wild pollinators in both agricultural and natural ecosystems, are declining worldwide. The global decline of bumblebees may threaten biodiversity, pollination services, and, ultimately, agricultural productivity. Several factors, including pesticide usage, climate change, habitat loss, and species invasion, have been documented in the decline of bumblebee species, but recent studies have revealed the dominating role of pathogens and parasites over any of these causes. Unfortunately, there is a lack of a full understanding of the role of pathogens and parasites in the decline of bumblebee species. The current study provides a comprehensive review of how pathogens and parasites contribute to the decline of bumblebee species. The study also explores the prevalence of each pathogen and parasite within bumblebee populations. Furthermore, we address the synergistic effects of pathogens and other stressors, such as pesticides, climatic effects, and habitat loss, on bumblebee populations. To summarize, we propose possible conservation and management strategies to preserve the critical role of bumblebees in pollination services and thus to support ecosystem and agricultural health.

Insecticide application prevents honey bees from realizing benefits of native forage in an agricultural landscape

Health and population status of bees is negatively affected by anthropogenic stressors, many of which co-occur in agricultural settings. While pollinator habitat (often involving plantings of native forbs) holds promise to benefit both managed and wild bees, important issues remain unresolved. These include whether conventional, broad-spectrum insecticide use negates these benefits and how non-native, managed honey bees affect wild bees in these areas. We conducted a three-year replicated study in a Midwestern corn and soybean production region (i.e., Iowa, USA). We assessed acute and delayed effects of commercial-scale spraying of a commonly used, foliar-applied insecticide (λ-cyhalothrin) in soybean on the productivity of honey bee colonies kept within these fields. Colony health metrics showed no immediate significant differences between insecticide treated and untreated crop fields. As expected, health metrics declined in all colonies after soybean ceased flowering. Interestingly, the subset of colonies from untreated fields given access to restored prairies rebounded. However, colonies from insecticide-treated fields showed reduced growth, queen egg-laying, and survival, even when given access to prairies. In addition, we did not observe a detectable impact of honey bee apiaries on wild bee abundance or diversity at these prairies over a three-year period. Our findings underscore the complex interactions between agricultural practices and bee health, highlighting the necessity of integrated pest management and the conservation of native floral resources to support pollinator populations and sustainable beekeeping in agroecosystems.

Ecological and anthropogenic drivers of local extinction and colonization of giant pandas over the past 30 years

Understanding the patterns and drivers of species range shifts is essential to disentangle mechanisms driving species' responses to global change. Here, we quantified local extinction and colonization dynamics of giant pandas (Ailuropoda melanoleuca) using occurrence data collected by harnessing the labor of >1000 workers and >60,000 worker days for each of the three periods (TP1: 1985-1988, TP2: 1998-2002, and TP3: 2011-2014), and evaluated how these patterns were associated with (1) protected area, (2) local rarity/abundance, and (3) abiotic factors (i.e., climate, land-use, and topography). We documented a decreased rate (from 0.433 during TP1-TP2 to 0.317 during TP2-TP3) of local extinction and a relatively stable rate (from 0.060 during TP1-TP2 to 0.056 during TP2-TP3) of local colonization through time. Furthermore, the occupancy gains have exceeded losses by a ratio of approximately 1.5 to 1, illustrating an expansion of panda's range at a rate of 1408.3 km2/decade. We also found that pandas were more likely to become locally extinct outside of protected areas, when locally rare in surrounding areas, and when certain biotic conditions were not met (e.g., increased forest cover). Local colonization was less likely in areas with high local rarity, challenging biotic conditions and unprotected area status. As the network of panda reserves expanded and the forest matured, the relative importance of other factors such as climate, biotic factors, and land-use became more influential in determining patterns of local extinction and colonization. Our findings provide insights into the factors governing the expansion of panda's range and illustrate how the relative influence of biotic and abiotic factors can change over time, indicating that effective conservation intervention may be able to mitigate some of the negative impacts of climate change and habitat degradation. This insight extends beyond pandas and highlights the role of conservation interventions can play in building resilience under a changing climate.

Lack of thermal acclimation in multiple indices of climate vulnerability in bumblebees

Indices of climate vulnerability are used to predict species' vulnerability to climate change based on intrinsic physiological traits, such as thermal tolerance, thermal sensitivity and thermal acclimation, but rarely is the consistency among indices evaluated simultaneously. We compared the thermal physiology of queen bumblebees between a species experiencing local declines (Bombus auricomus) and a species exhibiting continent-wide increases (B. impatiens). We conducted a multi-week acclimation experiment under simulated climate warming to measure critical thermal maximum (CTmax), critical thermal minimum (CTmin), the thermal sensitivity of metabolic rate and water loss rate and acclimation in each of these traits. We also measured survival throughout the experiment and after the thermal tolerance trials. Neither species acclimated to the temperature treatments by adjusting any physiological trait. We found conflicting patterns among indices of vulnerability within and between species. We also found that individuals with the highest CTmax exhibited the lowest survival following the thermal tolerance trial. Our study highlights inconsistent patterns across multiple indices of climate vulnerability within and between species, indicating that physiological studies measuring only one index of climate vulnerability may be limited in their ability to inform species' responses to environmental change.

Predicting the potential distribution of stingless bee, Tetragonula iridipennis in India using MaxEnt and CMIP6 climate projections

Tetragonula iridipennis Smith, commonly known as the stingless bee or 'dammer bee', is a key native species that pollinates a wide variety of horticultural crops, including onions, in India. Climate change significantly affects species distribution and habitat suitability. This study utilized Maximum Entropy Modeling (MaxEnt) to predict the current and future distribution of T. iridipennis in India. By modeling the species' potential distribution using both historical climate data (1970-2000) and future projections for 2050 and 2070 under two socio-economic scenarios, SSP126 (low-emission) and SSP585 (high-emission), the study provided accurate predictions. The area under the receiver operating characteristic curve (AUC) for model training and testing was 0.848 and 0.830, respectively, indicating strong model accuracy. Additionally, the Continuous Boyce Index (CBI) values for training and testing were 0.966 and 0.907, while the True Skill Statistic (TSS) values were 0.510 and 0.484. These metrics confirm that the model effectively distinguishes between suitable and unsuitable habitats for the species. The two most influential variables determining 84.9% of T. iridipennis's potential distribution were temperature seasonality (bio4; 66.2%) and mean temperature of the coldest quarter (bio11; 18.7%). The ideal zone for these variables were 155-170 and 13-28, respectively. The model indicated that the potential distribution of T. iridipennis is concentrated primarily in central and southern peninsular India, with the species' habitat predicted to expand under both SSP126 and SSP585 scenarios. This study provides a detailed overview of the current and potential future habitable areas for T. iridipennis in India, offering insights that could help guide conservation efforts for this important native pollinator.

Temperature-Related Bioclimatic Variables Play a Greater Role in the Spatial Distribution of Bumblebee Species in Northern Pakistan

Bumblebee species are vital wild pollinators, providing essential pollination services for various crops, fruits, and vegetables. However, their biodiversity is vulnerable to decline due to climate change, particularly in regions like northern Pakistan. Despite this, no research has yet been conducted on the distribution patterns of bumblebee species in this region. The current study aimed to model the spatial distribution of three important bumblebee species: Bombus haemorrhoidalis, B. rufofasciatus, and B. subtypicus in northern Pakistan. Habitat suitability and the contribution of bioclimatic variables to the spatial distribution of species were assessed using the MaxEnt approach. Current and future bioclimatic variables, along with presence-only records of three bumblebee species, were incorporated into the species distribution model. The results indicated that nearly 96% of the area (43 out of 45 cities in northern Pakistan) showed habitat suitability for all three species in the current scenario. Among these 43 cities, five exhibited a 100% overlap in suitable areas for the three species. However, this overlap area is expected to decrease in the future, particularly by the middle of the 21st century, highlighting these regions as prime candidates for conservation. In terms of bioclimatic factors influencing spatial distribution, the study found that temperature-related variables played a more significant role than precipitation-related ones in current and future scenarios. Specifically, bio3 (isothermality) contributed 48% to B. haemorrhoidalis and 43% to B. rufofasciatus, while bio2 (mean diurnal range) was the most influential factor for B. subtypicus. Temperature-related variables accounted for more than 80%, 69.4%, and 78.3% of the spatial variation in B. haemorrhoidalis, B. rufofasciatus, and B. subtypicus, respectively. This study demonstrates the critical influence of temperature on the spatial distribution of bumblebee species in northern Pakistan, underscoring the need for climate-focused conservation strategies to protect these important wild pollinators.

Bees remain heat tolerant after acute exposure to desiccation and starvation

Organisms may simultaneously face thermal, desiccation and nutritional stress under climate change. Understanding the effects arising from the interactions among these stressors is relevant for predicting organisms' responses to climate change and for developing effective conservation strategies. Using both dynamic and static protocols, we assessed for the first time how sublethal desiccation exposure (at 16.7%, 50.0% and 83.3% of LD50) impacts the heat tolerance of foragers from two social bee species found on the Greek island of Lesbos: the managed European honey bee, Apis mellifera, and the wild, ground-nesting sweat bee Lasioglossum malachurum. In addition, we explored how a short-term starvation period (24 h), followed by a moderate sublethal desiccation exposure (50% of LD50), influences honey bee heat tolerance. We found that neither the critical thermal maximum (CTmax) nor the time to heat stupor was significantly impacted by sublethal desiccation exposure in either species. Similarly, starvation followed by moderate sublethal desiccation did not affect the average CTmax estimate, but it did increase its variance. Our results suggest that sublethal exposure to these environmental stressors may not always lead to significant changes in bees' heat tolerance or increase vulnerability to rapid temperature changes during extreme weather events, such as heat waves. However, the increase in CTmax variance suggests greater variability in individual responses to temperature stress under climate change, which may impact colony-level performance. The ability to withstand desiccation may be impacted by unmeasured hypoxic conditions and the overall effect of these stressors on solitary species remains to be assessed.

Flumethrin exposure perturbs gut microbiota structure and intestinal metabolism in honeybees (Apis mellifera)

Flumethrin mitigates Varroa's harm to honeybee colonies; however, its residues in colonies threaten the fitness of honeybee hosts and gut microbiota. Our previous research has shown that flumethrin induces significant physiological effects on honeybee larvae; but the effects of flumethrin on the gut microbiota and metabolism of adult honeybees are still unknown. In this study, 1-day-old honeybees were exposed to 0, 0.01, 0.1, and 1 mg/L flumethrin for 14 days and the impacts of flumethrin on the intestinal system were evaluated. The results showed that exposure to 1 mg/L flumethrin significantly reduced honeybee survival and the activities of antioxidative enzymes (superoxide dismutase and catalase) and detoxification enzymes (glutathione S-transferase) in honeybee heads. Moreover, exposure to 0.01, 0.1, and 1 mg/L flumethrin significantly decreased the diversity of the honeybee gut microbiota. Results from untargeted metabolomics showed that long-term exposure to 0.01, 0.1, and 1 mg/L flumethrin caused changes in the metabolic pathways of honeybee gut microbes. Furthermore, increased metabolism of phenylalanine, tyrosine, and tryptophan derivatives was observed in honeybee gut microbes. These findings underscore the importance of careful consideration in using pesticides in apiculture and provide a basis for safeguarding honeybees from pollutants, considering the effects on gut microbes.

New York State Climate Impacts Assessment Chapter 03: Agriculture

Agriculture is a vital industry in New York State, which ranks among the top-producing states for dairy, fruits, and several other commodities. As agriculture depends on the weather and specific climatic conditions, this sector faces extraordinary challenges as New York's climate changes. This chapter explores the many impacts of a changing climate on agriculture, the ways these impacts interact with other challenges that New York farmers and farmworkers face, and opportunities for the agriculture industry to adapt and build resilience.

Cuticular Hydrocarbon Profiles of Himalayan Bumble Bees (Hymenoptera: Bombus Latreille) are Species-Specific and Show Elevational Variation

Bumble bees are important pollinators in natural environments and agricultural farmlands, and they are in particular adapted to harsh environments like high mountain habitats. In these environments, animals are exposed to low temperature and face the risk of desiccation. The Eastern Himalayas are one of the recognized biodiversity hotspots worldwide. The area covers subtropical rainforest with warm temperature and high precipitation as well as high mountain ranges with peaks reaching up to 7,000 m, shaping a diverse floral and faunal community at the different elevational zones. To identify possible adaptation strategies, we investigated the cuticular hydrocarbon profiles of four bumble bee species occurring at different elevational ranges in Arunachal Pradesh, the northeastern most state in India. At 17 locations along an elevational gradient, we collected workers of two species from lower elevations (B. albopleuralis and B. breviceps; ~ 100 m - 3,000 m asl) and two species from higher elevations (B. prshewalskyi and B. mirus; ~ 2,800 m - 4,500 m asl). The CHC profiles of all four species showed a significant degree of variation in the composition of hydrocarbons, indicating species specificity. We also found clear correlation with elevation. The weighted mean chain length of the hydrocarbons significantly differed between the low and high elevation species, and the proportion of saturated hydrocarbons in CHC profiles significantly increased with the elevational range of the bumble bee species. Our results indicate that bumble bees living at high elevations reduce the risk of water loss by adapting their CHC composition on their cuticle, a phenomenon that has also been found in other insects like ants and fruit flies.

The Interplay Between Visual Traits and Forest in Bumblebee Communities Across Sweden

Understanding how ecological communities assemble in relation to natural and human-induced environmental changes is critical, particularly for communities of pollinators that deliver essential ecosystem services. Despite widespread attention to interactions between functional traits and community responses to environmental changes, the importance of sensory traits has received little attention. To address this, we asked whether visual traits of bumblebee communities varied at large geographical scales along a habitat gradient of increased tree cover. Because trees generate challenging light conditions for flying insects, in particular a reduced light intensity, we hypothesised that differences in tree cover would correlate with shifts in the visual and taxonomical composition of bumblebee communities. We quantified 11 visual traits across 36 specimens from 20 species of bumblebees using micro-CT and optical modelling of compound eyes and ocelli, and investigated how these traits scale with body size. Using an inventory of bumblebee communities across Sweden and our visual trait dataset, we then explored how visual traits (both absolute and relative to body size) differed in relation to tree cover. We found positive shifts of the community weighted means of visual traits along the increasingly forested habitat gradient (facet diameter, inter-ommatidial angle, eye parameter of the compound eye and alignment of the three ocelli) that were consistent regardless of body size, while other traits decreased when more forest was present in the landscape (facet number). These functional patterns were associated with differences in the abundance of six common species that likely explains the community-wide shift of visual traits along the habitat gradient. Our study demonstrates the interaction between vision, habitat and community assembly in bumblebees, while highlighting a promising research topic at the interface between sensory biology and landscape ecology.

Rapid shifts in grassland communities driven by climate change

Many terrestrial plant communities, especially forests, have been shown to lag in response to rapid climate change. Grassland communities may respond more quickly to novel climates, as they consist mostly of short-lived species, which are directly exposed to macroclimate change. Here we report the rapid response of grassland communities to climate change in the California Floristic Province. We estimated 349 vascular plant species' climatic niches from 829,337 occurrence records, compiled 15 long-term community composition datasets from 12 observational studies and 3 global change experiments, and analysed community compositional shifts in the climate niche space. We show that communities experienced significant shifts towards species associated with warmer and drier locations at rates of 0.0216 ± 0.00592 °C yr-1 (mean ± s.e.) and -3.04 ± 0.742 mm yr-1, and these changes occurred at a pace similar to that of climate warming and drying. These directional shifts were consistent across observations and experiments. Our findings contrast with the lagged responses observed in communities dominated by long-lived plants and suggest greater biodiversity changes than expected in the near future.

Dying of thirst: Osmoregulation by a hawkmoth pollinator in response to variability in ambient humidity and nectar availability

Climate-induced shifts in flowering phenology can disrupt pollinator-floral resource synchrony, especially in desert ecosystems where rainfall dictates both. However, baseline metrics to gauge pollinator health in the wild amidst rapid climate change are lacking. Our laboratory-based study establishes a baseline for pollinator physiological state by exploring how osmotic conditions influence survivorship in a desert hawkmoth pollinator, Manduca sexta. We sampled hemolymph osmolality from over 1000 lab-grown moths at 20 %, 50 %, and 80 % ambient humidity levels. Starved moths maintained healthy osmolality of 350-400 mmol/kg for 1-3 days after eclosion regardless of ambient humidity, but it sharply rose to 550 mmol/kg after 4-5 days in low and moderate humidity, and after 5 days in high humidity. Starved moths in low humidity conditions perished within 5 days, while those in high humidity survived twice as long. Moths fed synthetic Datura wrightii nectar, synthetic Agave palmeri nectar, or water, maintained osmolality within a healthy range of 350-400mmol/kg. The same was true for moths fed authentic floral nectars from Datura and Agave plants, although moths consumed more synthetic than authentic nectars, possibly due to non-sugar constituents. Simulating a 4-day mismatch between pollinator emergence and nectar availability, a single nectar meal osmotically rescued moths under dry ambient conditions. Our findings highlight hemolymph osmolality as a rapid and accurate biomarker distinguishing dehydrated from hydrated states in insect pollinators.

Decline in diversity of tropical soil fauna under experimental warming

Climate change is exacerbating a global decline in biodiversity. Numerous observational studies link rising temperatures to declining biological abundance, richness and diversity in terrestrial ecosystems, yet few studies have considered the highly diverse and functionally significant communities of tropical forest soil and leaf litter fauna. Here, we report major declines in the order-level richness and diversity of soil and leaf litter fauna following three years of experimental whole-profile soil warming in a tropical forest. These declines were greatest during the dry season, suggesting that warming effects could be exacerbated by drought. Contrary to findings from higher latitudes, total faunal abundance increased under warming, and these effects were paralleled by major shifts in community composition. These responses were driven by increased dominance of a relatively small number of thermophilic taxa, and of oribatid mites in particular. Our study provides direct experimental evidence that warming causes diversity declines and compositional shifts for tropical forest soil and leaf litter fauna, a result with potential consequences for soil functions and biogeochemical cycles, and that highlights the vulnerability of tropical biodiversity to climate change.

Analysis of contaminant residues in honey bee hive matrices

Pollinators provide ecological services essential to maintaining our food supply and propagating natural habitats. Populations are in decline due to environmental stressors including pesticides, pathogens, and habitat loss. To better understand the impacts of pesticide exposures on colony health, a field survey in Ohio, USA was conducted to monitor the potential contamination of honey bee colonies by pesticides. Apiaries (n = 10) were situated across an agricultural gradient and samples were collected over a 4-week period encompassing corn planting. Dead bees from entrance traps (DBT), pollen, and in-hive (IH) matrices including bee bread, honey, larvae, and nurse bees were analyzed for a whole suite of pesticides. Out of 210 pesticides targeted, 68 residues were quantified across 306 samples. Neonicotinoids, miticides, and fungicides were the dominant pesticide classes identified throughout all the matrix types. Neonicotinoids were detected at higher concentrations and at higher frequencies compared to fungicides, specifically in field pollen samples. DBT also contained high concentrations of these two contaminant classes, although detection frequencies for neonicotinoids were typically lower. Overall, herbicides and non‑neonicotinoid insecticides were found with low frequency and at low concentrations. For most pesticide classes, trends for the mean concentrations were DBT > IH nurse bees > field pollen > IH larvae > IH honey. Pesticides were detected in 100 % of samples with concentrations ranging from 0.01 ppb (diphenylamine) to 2790 ppb (clothianidin). All samples were contaminated with at least two pesticide residues, while 19 samples presented over ten detects and maximum detections of 20 in DBT. Pesticide residues were positively correlated with agricultural gradients across sites and sampling periods. These findings reveal that foraging leads to the exposure of the entire colony to a wide range of pesticides. Moreover, residues determined in DBT serve as an effective proxy for monitoring hive matrices with significantly less disturbance to active hives.

Negative and sex-specific effects of drought on flower production, resources and pollinator visitation, but not on floral scent in monoecious Cucurbita pepo

The globally changing climatic condition is increasing the incidences of drought in several parts of the world. This is predicted and already shown to not only impact plant growth and flower development, but also plant-pollinator interactions and the pollination success of entomophilous plants. However, there is a large gap in our understanding of how drought affects the different flowers and pollen transfer among flowers in sexually polymorphic species. Here, we evaluated in monoecious Styrian oil pumpkin, and separately for female and male flowers, the responses of drought stress on flower production, petal size, nectar, floral scent and visitation by bumblebee pollinators. Drought stress adversely affected all floral traits studied, except floral scent. Although both flower sexes were adversely affected by drought stress, the effects were more severe on female flowers, with most of the female flowers even aborted before opening. The drought had negative effects on floral visitation by the pollinators, which generally preferred female flowers. Overall, our study highlights that the two flower sexes of a monoecious plant species are differently affected by drought stress and calls for further investigations to better understand the cues used by the pollinators to discriminate against male flowers and against flowers of drought-stressed plants.

How does climate change impact social bees and bee sociality?

Climatic factors are known to shape the expression of social behaviours. Likewise, variation in social behaviour can dictate climate responses. Understanding interactions between climate and sociality is crucial for forecasting vulnerability and resilience to climate change across animal taxa. These interactions are particularly relevant for taxa like bees that exhibit a broad diversity of social states. An emerging body of literature aims to quantify bee responses to environmental change with respect to variation in key functional traits, including sociality. Additionally, decades of research on environmental drivers of social evolution may prove fruitful for predicting shifts in the costs and benefits of social strategies under climate change. In this review, we explore these findings to ask two interconnected questions: (a) how does sociality mediate vulnerability to climate change, and (b) how might climate change impact social organisation in bees? We highlight traits that intersect with bee sociality that may confer resilience to climate change (e.g. extended activity periods, diet breadth, behavioural thermoregulation) and we generate predictions about the impacts of climate change on the expression and distribution of social phenotypes in bees. The social evolutionary consequences of climate change will be complex and heterogeneous, depending on such factors as local climate and plasticity of social traits. Many contexts will see an increase in the frequency of eusocial nesting as warming temperatures accelerate development and expand the temporal window for rearing a worker brood. More broadly, climate-mediated shifts in the abiotic and biotic selective environments will alter the costs and benefits of social living in different contexts, with cascading impacts at the population, community and ecosystem levels.

Important Crop Pollinators Respond Less Negatively to Anthropogenic Land Use Than Other Animals

Animal-mediated pollination is a key ecosystem service required to some extent by almost three-quarters of the leading human food crops in global food production. Anthropogenic pressures such as habitat loss and land-use intensification are causing shifts in ecological community composition, potentially resulting in declines in pollination services and impacting crop production. Previous research has often overlooked interspecific differences in pollination contribution, yet such differences mean that biodiversity declines will not necessarily negatively impact pollination. Here, we use a novel species-level ecosystem service contribution matrix along with mixed-effects models to explore how groups of terrestrial species who contribute differently to crop pollination respond globally to land-use type, land-use intensity, and availability of natural habitats in the surrounding landscape. We find that the species whose contribution to crop pollination is higher generally respond less negatively (and in some cases positively) to human disturbance of land, compared to species that contribute less or not at all to pollination. This result may be due to these high-contribution species being less sensitive to anthropogenic land conversions, which has led humans to being more reliant on them for crop pollination. However, it also suggests that there is potential for crop pollination to be resilient in the face of anthropogenic land conversions. With such a high proportion of food crops requiring animal-mediated pollination to some extent, understanding how anthropogenic landscapes impact ecological communities and the consequences for pollination is critical for ensuring food security.

Wind energy and insects: reviewing the state of knowledge and identifying potential interactions

In 2023 the wind industry hit a milestone of one terawatt of installed capacity globally. That amount is expected to double within the next decade as billions of dollars are invested in new wind projects annually. Wildlife mortality is a primary concern regarding the proliferation of wind power, and many studies have investigated bird and bat interactions. Little is known about the interactions between wind turbines and insects, despite these animals composing far more biomass than vertebrates. Turbine placement, coloration, shape, heat output, and lighting may attract insects to turbines. Insects attract insectivorous animals, which may be killed by the turbines. Compiling current knowledge about these interactions and identifying gaps in knowledge is critical as wind power grows rapidly. We reviewed the state of the literature investigating insects and wind energy facilities, and evaluated hypotheses regarding insect attraction to turbines. We found evidence of insect attraction due to turbine location, paint color, shape, and temperature output. We provide empirical data on insect abundance and richness near turbines and introduce a risk assessment tool for comparing wind development with suitable climate for insects of concern. This understudied topic merits further investigation as insects decline globally. Compiling information will provide a resource for mitigation and management strategies, and will inform conservation agencies on what insects may be most vulnerable to the expansion of wind technologies.

Examining the Effects of Environment, Geography, and Elevation on Patterns of DNA Methylation Across Populations of Two Widespread Bumble Bee Species

Understanding the myriad avenues through which spatial and environmental factors shape evolution is a major focus in biological research. From a molecular perspective, much work has been focused on genomic sequence variation; however, recently there has been increased interest in how epigenetic variation may be shaped by different variables across the landscape. DNA methylation has been of particular interest given that it is dynamic and can alter gene expression, potentially offering a path for a rapid response to environmental change. We utilized whole genome enzymatic methyl sequencing to evaluate the distribution of CpG methylation across the genome and to analyze patterns of spatial and environmental association in the methylomes of two broadly distributed montane bumble bees (Bombus vancouverensis Cresson and Bombus vosnesenskii Radoszkowski) across elevational gradients in the western US. Methylation patterns in both species are similar at the genomic scale with ∼1% of CpGs being methylated and most methylation being found in exons. At the landscape scale, neither species exhibited strong spatial or population structuring in patterns of methylation, although some weak relationships between methylation and distance or environmental variables were detected. Differential methylation analysis suggests a stronger environment association in B. vancouverensis given the larger number of differentially methylated CpG's compared to B. vosnesenskii. We also observed only a handful of genes with both differentially methylated CpGs and previously detected environmentally associated outlier SNPs. Overall results reveal a weak but present pattern in variation in methylation over the landscape in both species.

Climate change effects on the diversity and distribution of soybean true bugs pests

BACKGROUND

Climate change and pests are two major factors in the reduction of global soybean yields. The diversity and geographic distribution of soybean true bug pests vary across soybean production areas worldwide, and climate change impacts are different across species and regions. Therefore, we integrated spatial and temporal predictions at the global scale to predict the impact of global warming on the distribution of 84 soybean true bug pests by the maximum entropy niche model (MaxEnt) under present (1970-2000) and future (2041-2060) scenarios. We produced an ensemble projection of the potential distribution of pests and crop production areas to estimate how and where climate warming will augment the threat of soybean true bug pests to soybean production areas.

RESULTS

Our results indicated that Southeast North America, Central South America, Europe and East Asia were the regions with the higher richness of soybean true bug and the most vulnerable areas to invasion threats. Climate change would promote the expansion of the distribution range and facilitate pest movement pole wards, affecting more soybean cultivated areas located in mid-latitudes. Moreover, species with different distribution patterns responded differently to climate change in that large-ranged species tended to increase in occupancy over time, whereas small-ranged species tended to decrease.

CONCLUSION

This result indicates that some pests that have not yet become notable may have the chance to develop into serious pests in the future due to the expansion of their geographical range. Our findings highlight that soybean cultivated regions at mid-latitudes would face general infestations from soybean true bug pests under global warming. These results will further facilitate the formulation of adaptation planning to minimize local environmental impacts in the future. © 2024 Society of Chemical Industry.

Conservation genomics analysis reveals recent population decline and possible causes in bumblebee Bombus opulentus

Bumblebees are a genus of pollinators (Bombus) that play important roles in natural ecosystem and agricultural production. Several bumblebee species have been recorded as under population decline, and the proportion of species experiencing population decline within subgenus Thoracobombus is higher than average. Bombus opulentus is 1 species in Thoracobombus, but little is known about its recent population dynamics. Here, we employed conservation genomics methods to investigate the population dynamics of B. opulentus during the recent past and identify the likely environmental factors that may cause population decline. Firstly, we placed the scaffold-level of B. opulentus reference genome sequence onto chromosome-level using Hi-C technique. Then, based on this reference genome and whole-genome resequencing data for 51 B. opulentus samples, we reconstructed the population structure and effective population size (Ne) trajectories of B. opulentus and identified genes that were under positive selection. Our results revealed that the collected B. opulentus samples could be divided into 2 populations, and 1 of them experienced a recent population decline; the declining population also exhibited lower genetic diversity and higher inbreeding levels. Genes related to high-temperature tolerance, immune response, and detoxication showed signals of positive selection in the declining population, suggesting that climate warming and pathogen/pesticide exposures may contribute to the decline of this B. opulentus population. Taken together, our study provided insights into the demography of B. opulentus populations and highlighted that populations of the same bumblebee species could have contrasting Ne trajectories and population decline could be caused by a combination of various stressors.

Flower Visitation through the Lens: Exploring the Foraging Behaviour of Bombus terrestris with a Computer Vision-Based Application

To understand the processes behind pollinator declines and for the conservation of pollination services, we need to understand fundamental drivers influencing pollinator behaviour. Here, we aimed to elucidate how wild bumblebees interact with three plant species and investigated their foraging behaviour with varying flower densities. We video-recorded Bombus terrestris in 60 × 60 cm quadrats of Lotus creticus, Persicaria capitata, and Trifolium pratense in urban areas of Terceira (Azores, Portugal). For the automated bumblebee detection and counting, we created deep learning-based computer vision models with custom datasets. We achieved high model accuracy of 0.88 for Lotus and Persicaria and 0.95 for Trifolium, indicating accurate bumblebee detection. In our study, flower cover was the only factor that influenced the attractiveness of flower patches, and plant species did not have an effect. We detected a significant positive effect of flower cover on the attractiveness of flower patches for flower-visiting bumblebees. The time spent per unit of inflorescence surface area was longer on the Trifolium than those on the Lotus and Persicaria. However, our result did not indicate significant differences in the time bumblebees spent on inflorescences among the three plant species. Here, we also justify computer vision-based analysis as a reliable tool for studying pollinator behavioural ecology.

Global changes and their environmental stressors have a significant impact on soil biodiversity-A meta-analysis

Identifying the main threats to soil biodiversity is crucial as soils harbor ∼60% of global biodiversity. Many previous meta-analyses investigating the impact of different global changes (GCs) on biodiversity have omitted soil fauna or are limited by the GCs studied. We conducted a broad-scale meta-analysis focused on soil fauna communities, analyzing 3,161 effect sizes from 624 publications studying climate change, land-use intensification, pollution, nutrient enrichment, invasive species and habitat fragmentation. Land-use intensification resulted in large reductions in soil fauna communities, especially for the larger-bodied groups. Unexpectedly, pollution caused the largest negative impact on soil biodiversity - particularly worrying due to continually increasing levels of pollution and poor mechanistic understanding of impacts relative to other GCs. Not all GCs and stressors were detrimental; organic-based nutrient enrichment often resulted in positive responses. Including soil biodiversity in large-scale analyses is vital to fully understand the impact of GCs across the different realms.

Consumption of pollen contaminated with field-realistic concentrations of fungicide causes sublethal effects in Bombus impatiens (Hymenoptera: Apidae) microcolonies

Bumble bees are declining across the globe. The causes of this decline have been attributed to a variety of stressors, including pesticides. Fungicides are a type of pesticide that has been understudied in the context of bumble bee health. As a result, fungicides are often applied to flowering plants without consideration of pollinator exposure. Recent work demonstrates that fungicides have sublethal effects in bumble bees, but little is known about how much fungicide it takes to cause these sublethal effects. To address this gap in the literature, we fed microcolonies of the common eastern bumble bee (Bombus impatiens CressonHymenoptera: ApidaeHymenoptera: ApidaeHymenoptera: ApidaeHymenoptera: Apidae) pollen contaminated with a range of fungicide concentrations. We chose these concentrations based on the range of fungicide concentrations in pollen and nectar that were reported in the literature. Results revealed that later-stage pupae and newly emerged males are potentially sensitive to fungicide exposure, showing smaller size and reduced fat reserves at intermediate levels of contamination. Compared to the control, intermediated levels of fungicide-contaminated pollen led to increased pupal mortality and delayed male emergence. Contrary to expectations, higher fungicide levels did not exhibit a linear relationship with negative impacts, suggesting nuanced effects. Because body size and emergence timing are important aspects of bumble bee reproductive behavior, results have implications for mating success, potentially disrupting colony development.

The heat is on: reduced detection of floral scents after heatwaves in bumblebees

Global climate change disrupts key ecological processes and biotic interactions. The recent increase in heatwave frequency and severity prompts the evaluation of physiological processes that ensure the maintenance of vital ecosystem services such as pollination. We used experimental heatwaves to determine how high temperatures affect the bumblebees' ability to detect floral scents. Heatwaves induced strong reductions in antennal responses to floral scents in both tested bumblebee species (Bombus terrestris and Bombus pascuorum). These reductions were generally stronger in workers than in males. Bumblebees showed no consistent pattern of recovery 24 h after heat events. Our results suggest that the projected increased frequency and severity of heatwaves may jeopardize bumblebee-mediated pollination services by disrupting the chemical communication between plants and pollinators. The reduced chemosensitivity can decrease the bumblebees' abilities to locate food sources and lead to declines in colonies and populations.

Climate change, temperature extremes, and impacts on hyperparasitoids

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

Size-dependent responses of colony-founding bumblebee (Bombus impatiens) queens to exposure to pesticide residues in soil during hibernation

Bumblebees and other key pollinators are experiencing global declines, a phenomenon driven by multiple environmental stressors, including pesticide exposure. While bumblebee queens spend most of their life hibernating underground, no study to date has examined how exposure to pesticide-contaminated soils might affect bumblebee queens during this solitary phase of their lifecycle. We exposed Bombus impatiens queens (n = 303) to soil treated with field-realistic concentrations of two diamide insecticides (chlorantraniliprole and cyantraniliprole) and two fungicides (boscalid and difenoconazole), alone or combined, during a 30-week hibernation period. We found that exposure to boscalid residues in soil doubled the likelihood of queens surviving through the colony initiation period (after successful hibernation) and laying eggs. Our data also revealed complex interactions between pesticide exposure and queen body mass on aspects of colony founding. Among others, exposure to cyantraniliprole led to lethal and sublethal post-hibernation effects that were dependent on queen size, with larger queens showing higher mortality rates, delayed emergence of their first brood, and producing smaller workers. Our results show that effects of pesticide exposure depend on intrinsic traits of bumblebee queen physiology and challenge our understanding of how bees respond to pesticides under environmentally realistic exposure scenarios.

The Impact of High-Temperature Stress on the Growth and Development of Tuta absoluta (Meyrick)

Insect life processes and reproductive behaviors are significantly affected by extremely high temperatures. This study focused on Tuta absoluta, which poses a severe threat to tomato cultivars. The effects of intense heat stress on the growth, development, oviposition, and longevity of T. absoluta were investigated. This investigation encompassed various developmental stages, including eggs, pupae, and adults. This study revealed that egg hatching and pupa emergence rates were significantly reduced at a temperature of 44 °C maintained for 6 h. The longevity of adults that emerged after the egg and pupal stages were exposed to 44 °C for 6 h was significantly reduced compared to the control. Notably, there was no significant variation in adult fecundity after egg-stage exposure to high temperatures. However, all treatments exhibited significantly reduced fecundity compared to the control after exposure to high temperatures during the pupal stage. Adult survival rates after exposure to 40 °C and 44 °C for 3 h were 74.29% and 22.40%, respectively, dramatically less than that of the control, which was 100%. However, no significant differences were noted in terms of longevity and egg production. These results offer a better understanding of the complex interactions between extreme temperatures and the life history traits of T. absoluta, thereby offering valuable insights for implementing management strategies to alleviate its impact on tomato crops in response to climate change.

Novel indices reveal that pollinator exposure to pesticides varies across biological compartments and crop surroundings

Declines in insect pollinators have been linked to a range of causative factors such as disease, loss of habitats, the quality and availability of food, and exposure to pesticides. Here, we analysed an extensive dataset generated from pesticide screening of foraging insects, pollen-nectar stores/beebread, pollen and ingested nectar across three species of bees collected at 128 European sites set in two types of crop. In this paper, we aimed to (i) derive a new index to summarise key aspects of complex pesticide exposure data and (ii) understand the links between pesticide exposures depicted by the different matrices, bee species and apple orchards versus oilseed rape crops. We found that summary indices were highly correlated with the number of pesticides detected in the related matrix but not with which pesticides were present. Matrices collected from apple orchards generally contained a higher number of pesticides (7.6 pesticides per site) than matrices from sites collected from oilseed rape crops (3.5 pesticides), with fungicides being highly represented in apple crops. A greater number of pesticides were found in pollen-nectar stores/beebread and pollen matrices compared with nectar and bee body matrices. Our results show that for a complete assessment of pollinator pesticide exposure, it is necessary to consider several different exposure routes and multiple species of bees across different agricultural systems.

Ornithomya biloba, Pseudolynchia garzettae and Pseudolynchia canariensis (Diptera: Hippoboscidae): three new United Kingdom colonists and potential disease vectors

In the northern hemisphere, many species' ranges are shifting northwards with climate change. Here I present evidence, from the first large-scale citizen science study of the Hippoboscidae in the United Kingdom, for the colonisation of the United Kingdom by three species of Diptera in the family Hippoboscidae, which are obligate ectoparasites of birds. The Swallow Louse Fly, Ornithomya biloba; the Nightjar Louse Fly, Pseudolynchia garzettae and the Pigeon Louse Fly, Pseudolynchia canariensis were previously considered to be vagrants from more southerly latitudes but the presence of a pair taken possibly in the act of copulation, gravid females and the increase in numbers of the various species provides good evidence of local breeding activity. I discuss the potential for further northwards range shift and whether the presence of three new species of parasite may have implications for the spread of avian disease within the region. I also include a concise key to the genus Pseudolynchia and images of P. canariensis, P. garzettae and O. biloba to aid further identification of these species in the region.

Extreme heat exposure of host plants indirectly reduces solitary bee fecundity and survival

Extreme heat poses a major threat to plants and pollinators, yet the indirect consequences of heat stress are not well understood, particularly for native solitary bees. To determine how brief exposure of extreme heat to flowering plants affects bee behaviour, fecundity, development and survival we conducted a no-choice field cage experiment in which Osmia lignaria were provided blueberry (Vaccinium corymbosum), phacelia (Phacelia tanacetifolia) and white clover (Trifolium repens) that had been previously exposed to either extreme heat (37.5°C) or normal temperatures (25°C) for 4 h during early bloom. Despite a similar number of open flowers and floral visitation frequency between the two treatments, female bees provided with heat-stressed plants laid approximately 70% fewer eggs than females provided with non-stressed plants. Their progeny received similar quantities of pollen provisions between the two treatments, yet larvae consuming pollen from heat-stressed plants had significantly lower survival as larvae and adults. We also observed trends for delayed emergence and reduced adult longevity when larvae consumed heat-stressed pollen. This study is the first to document how short, field-realistic bursts of extreme heat exposure to flowering host plants can indirectly affect bee pollinators and their offspring, with important implications for crop pollination and native bee populations.

Temperature influences desiccation resistance of bumble bees

Ongoing climate change has increased temperatures and the frequency of droughts in many parts of the world, potentially intensifying the desiccation risk for insects. Because resisting desiccation becomes more difficult at higher temperatures and lower humidity, avoiding water loss is a key challenge facing terrestrial insects. However, few studies have examined the interactive effects of temperature and environmental humidity on desiccation resistance in insects. Such studies on bees (Hymenoptera: Apoidea: Anthophila) are especially rare, despite their ecological and economic importance. Here, we crossed temperature (20, 25, and 30 °C) with humidity (<5, 50, >95 % RH) manipulations and measured time to mortality, water loss rates, and the water content at mortality of bumble bees (Bombus impatiens). We found that both higher temperature and lower humidity increased water loss rates, while warmer temperatures reduced survival time and lower humidity decreased water content at mortality. Additionally, we observed large intraspecific variation in water balance traits between colonies, and larger individuals survived longer and could tolerate more water loss before mortality. This study raises important questions about the mechanisms underpinning water loss in bumble bees and suggests that frequent access to nectar may be especially important for bumble bees' water balance and survival in a warming and drying climate.

KC. Heat exposure limits pentose phosphate pathway activity in bumblebees

Bumblebee populations across the globe are experiencing substantial declines due to climate change, with major consequences for pollination services in both natural and agricultural settings. Using an economically important species, Bombus impatiens, we explored the physiological mechanisms that may cause susceptibility to extreme heat events. We tested the hypothesis that heat exposure limits the activity of the pentose phosphate pathway (PPP)-a parallel pathway to glycolysis that can use nectar sugar to generate antioxidant potential and combat oxidative stress. Using isotopically labelled glucose, we tracked PPP activity in B. impatiens at rest, during exercise and during a post-exercise recovery period under two different temperature regimes (22°C and 32°C). We found that the PPP is routinely used by B. impatiens at moderate temperatures, but that its activity is markedly reduced when ATP demands are high, such as during periods of exercise and heat exposure. We also exposed B. impatiens to either 22°C or 32°C for 5 hours and assessed levels of oxidative damage (lipid peroxidation, protein carbonyls) and antioxidant potential [reduced (GSH) and oxidized (GSSG) glutathione concentrations]. Interestingly, bees exhibited little oxidative damage after the thermal exposure, but we found a lower GSH:GSSG ratio in 32°C-exposed bees, reflecting lower antioxidant potential. Overall, our study demonstrates that acute heat stress severely limits PPP activity and may constrain antioxidant potential in B. impatiens. The repeated attenuation of this pathway in a warming climate may have more severe physiological consequences for this species, with potential implications for pollination services across North America.

Bumble Bee Watch community science program increases scientific understanding of an important pollinator group across Canada and the USA

In a time of increasing threats to bumble bees (Hymenoptera: Apidae: Bombus), it is important to understand their ecology and distribution. As experts are limited in resources to conduct field surveys, there is potential for community scientists to help. The Bumble Bee Watch (BBW) community science program involves volunteers taking photos of bumble bees in Canada and the USA and submitting them, along with geographic and optional plant information, to a website or through an app. Taxon experts then verify the bee species identification. The Bumble Bees of North America database (BBNA) stores data (no photographs) collected and identified by more traditional scientific methods over the same range. Here we compared BBW data to BBNA data over all years and just 2010-2020 to understand the scientific contribution of community scientists to the state of the knowledge about native bumble bees. We found that BBW had similar geographic and species coverage as BBNA. It had records from all 63 provinces, states, and territories where bumble bees occur (including four more than BBNA in 2010-2020), and represented 41 of the 48 species in BBNA (with ten more species than BBNA in 2010-2020). While BBW contributed only 8.50% of records overall, it contributed 25.06% of all records over 2010-2020. BBW confirmed the persistence of species and identified new locations of species, both inside and outside of the previously known extent of occurrences. BBW also contributed a wealth of ecological information, such as unique plant genera and species data for almost all the bee species. Thus, while BBW had fewer bee records than the BBNA database overall, it helped to fill in data gaps and provided novel information, complementing the traditional methods. This community science program is valuable in helping to inform conservation management for bumble bee species.

Predicted range expansion of Prostephanus truncatus (Coleoptera: Bostrichidae) under projected climate change scenarios

The larger grain borer (Prostephanus truncatus [Horn] [Coleoptera: Bostrichidae]) is a wood-boring insect native to Central America and adapted to stored maize and cassava. It was accidentally introduced to Tanzania and became a pest across central Africa. Unlike many grain pests, P. truncatus populations can establish and move within forests. Consequently, novel infestations can occur without human influence. The objectives of our study were to (i) develop an updated current suitability projection for P. truncatus, (ii) assess its potential future distribution under different climate change scenarios, and (iii) identify climate variables that best inform the model. We used WALLACE and MaxEnt to predict potential global distribution by incorporating bioclimatic variables and occurrence records. Future models were projected for 2050 and 2070 with Representative Concentration Pathways (RCPs) 2.6 (low change) and 8.5 (high change). Distribution was most limited by high precipitation and cold temperatures. Globally, highly suitable areas (> 75%) primarily occurred along coastal and equatorial regions with novel areas in northern South America, India, southeastern Asia, Indonesia, and the Philippines, totaling 7% under current conditions. Highly suitable areas at RCPs 2.6 and 8.5 are estimated to increase to 12% and 15%, respectively, by 2050 and increase to 19% in 2070 under RCP 8.5. Centroids of highly suitable areas show distribution centers moving more inshore and away from the equator. Notably, the result is a range expansion, not a shift. Results can be used to decrease biosecurity risks through more spatially explicit and timely surveillance programs for targeting the exclusion of this pest.

Effects of common co-occurring pesticides (a neonicotinoid and fungicide) on honey bee colony health in a semi-field study

Multiple stressors are linked to declines of insects and important pollinators, such as bees. Recently, interactive effects of multiple agrochemicals on bees have been highlighted, including fungicides, which increase toxicity of neonicotinoid insecticides. Here, we use a semi-field study across two seasons in controlled foraging tunnels to test the effects of a field application of a commercial fungicide product with two active ingredients (pyraclostrobin and metconazole) applied at label rates. We also examine its interactive effects with the neonicotinoid insecticide clothianidin, at a conservative field-realistic dose of 2.23 ppb, on 48 honey bee colonies. We found combined effects of pesticide exposure, including additive 2.93-fold increases in mortality, and an additional effect of increased infestation levels of the ectoparasitic mite, Varroa destructor. Pesticide treatments also reduced colony activity, reduced colony weight, and increased sugar consumption of whole colonies. These findings indicate that typical sublethal exposure levels to common, co-occurring agrochemicals in the field significantly affect the health of whole honey bee colonies, highlighting an unintended consequence of increasing pesticide applications.