Bombus Research Articles

Resistance to Varroa destructor is a trait mainly transmitted by the queen and not via worker learning

How beekeepers can propagate the Varroa-resistant traits they have in their colonies depends on how varroa resistance, i.e. the key hygienic behavioural traits, is passed onto the next generation. This study investigates if the key hygienic traits are passed between workers via learning as is known to happen in bumble bees, or are the resistant traits encoded into the queens and thus her offspring. To test this, we re-queened known mite-resistant colonies with mite-naïve (susceptible) queens in both Hawaii and the UK. We also placed resistant queens in susceptible colonies in the UK. After 5 months in Hawaii and 12 months in the UK, mite levels in adults and brood were measured. In Hawaii, mite removal and cell recapping levels were also assessed. In both locations, the mite levels in colonies headed by suspectable (mite-naïve) queens or their daughters significantly exceeded that found in colonies headed by resistant queens or their daughters. The initial presence of resistant or suspectable workers did not affect the result. Therefore, to propagate mite-resistant traits, beekeepers only need to re-queen a colony with a locally mated queen from an established resistant population, as some UK and Hawaiian beekeepers are already doing.

Caste-specific development of the dopaminergic system in bumble bees (Bombus ignitus)

The dopaminergic system is involved in caste-specific behaviors in eusocial bumble bees. However, little is known about how the caste differences in dopaminergic system are formed during pupal stages in the brains of bumble bees. Thus, we investigated the levels of dopamine-related substances and expression of genes encoding enzymes involved in dopamine synthesis and metabolism, dopamine receptors, and a dopamine transporter in the brain of female Bombus ignitus. The levels of dopamine and dopamine-related substances in the brain were significantly higher in gynes than in workers from the late pupal stage to emergence, but the dynamics were similar between the castes. The relative expression levels of genes encoding enzymes involved in dopamine synthesis (BigTh and BigDdc) and dopamine metabolism (BigNat) increased significantly from pupal stage to emergence, but there were no differences in the relative expression levels of these genes between castes. A similar pattern was seen in the relative expression levels of four dopamine receptor genes (BigDop1, BigDop2, BigDop3, and BigDopEcR) and a dopamine transporter gene (BigDat). Compared with the honey bee Apis mellifera, the caste-specific dopaminergic system in the bumble bee is less differentiated, which might reflect the degree of behavioral specialization in these two species.

Does coevolution in refugia drive mimicry in bumble bees? Insights from a South Asian mimicry group.

Müllerian mimicry was proposed to be an example of a coevolved mutualism promoted by population isolation in glacial refugia. This, however, has not been well supported in butterfly models. Here, we use genomic data to test this theory while examining the population genetics behind mimetic diversification in a pair of co-mimetic bumble bees, Bombus breviceps Smith and Bombus trifasciatus Smith. In both lineages, populations were structured by geography but not as much by color pattern, suggesting sharing of color alleles across regions of restricted gene flow and formation of mimicry complexes in the absence of genetic differentiation. Demographic analyses showed mismatches between historical effective population size changes and glacial cycles, and niche modeling revealed only mild habitat retraction during glaciation. Moreover, mimetic subpopulations of the same color form in the two lineages only in some cases exhibit similar population history and genetic divergence. Therefore, the current study supports a more complex history in this comimicry than a simple refugium-coevolution model.

Fecal sampling protocol to assess bumble bee health in conservation research

Fecal sampling protocol to assess bumble bee health in conservation research

Comparison of nectar and pollen resources in various Tilia species. A case study from southern Poland

Management of food resources is considered fundamental for supporting insect pollinators, whose abundance shows a downward trend on the global scale. Here, the nectar and pollen production (per flower, per 1 m2 of tree crown), the composition of nectar carbohydrates and the levels of pollen proteins was evaluated in eight Tilia species (Malvaceae) growing in SE Poland. In the warm-summer continental climate, Tilia species can improve nectar and pollen resources mainly in June/July. Although the flowering period of each species is short (8.0–14.7 days), appropriate selection of species can extend the availability of food for more than a month. However, the considerable variations in the flowering onset (11.2–20.1 days) may cause significant inter-seasonal shifts in food accessibility.The nectar with its highly changeable sugar concentration (29.5–77.4%) was composed of sucrose, glucose, and fructose; protein content in pollen was 7.2–16.8%. The mean sugar yield was in the range of 0.95–19.1 g per 1 m2 (T. amuriensis – T. platyphyllos, respectively), whereas the mean pollen yield was 1.37–4.1 g per 1 m2 of tree crown (T. amuriensis – T. × euchlora, respectively). Significant year-to-year fluctuations of sugar and pollen yield in linden trees have to be taken into account in conservation schemes, and the introduction of other flowering plants with more stable sugar and pollen production should be considered in an area with a high density of linden trees. Linden flowers mainly support honey bees; nevertheless, wild pollinators (bumble bees, solitary bees, and dipterans) can also benefit from linden floral resources.

Cadmium soil contamination alters plant-pollinator interactions

Soil heavy metal contamination is often an unintended byproduct of historic land-use. This contamination can negatively impact resident plants and their interactions with other organisms. Plant fitness in contaminated landscapes depends not only on plant growth, but also on the maintenance of interactions with pollinators. Cadmium (Cd) is a heavy metal that is commonly found in agricultural, urban, and industrial ecosystems as a legacy of historic land-use. It is a prioritized pollutant in soils because of its wide distribution and strong biotoxicity. To understand how Cd influences plant growth and pollinator interactions, we grew sunflowers in media with three different Cd concentrations to represent the range of Cd contamination faced by sunflowers growing on land recovering from past land-use. We measured Cd contamination effects on sunflower morphology and pollinator foraging behavior, specifically the number of visits and visit duration. We then measured seed number and weight to determine if contamination directly or indirectly, as mediated by pollinators, altered plant fitness. Plant height was negatively correlated with Cd concentration, but contamination alone (in the absence of pollinators) did not affect sunflower reproduction. Bumble bees visited sunflowers grown in Exceeding Threshold Cd concentrations less often and for shorter time compared to visits to Below Threshold Cd sunflowers, but honey bees and sweat bees showed similar foraging behavior across Cd contamination treatment levels. Sunflower seed set was positively correlated with the total number of pollinator visits, and sunflowers grown in Exceeding Threshold Cd soil had marginally lower seed set compared to those grown in Below Threshold Cd soil. Our results suggest that at Exceeding Threshold Cd contamination levels plant-pollinator interactions are negatively affected with consequences for plant fitness.

From pollen to putrid: Comparative metagenomics reveals how microbiomes support dietary specialization in vulture bees.

For most animals, the microbiome is key for nutrition and pathogen defence, and is often shaped by diet. Corbiculate bees, including honey bees, bumble bees, and stingless bees, share a core microbiome that has been shaped, at least in part, by the challenges associated with pollen digestion. However, three species of stingless bees deviate from the general rule of bees obtaining their protein exclusively from pollen (obligate pollinivores) and instead consume carrion as their sole protein source (obligate necrophages) or consume both pollen and carrion (facultative necrophages). These three life histories can provide missing insights into microbiome evolution associated with extreme dietary transitions. Here, we investigate, via shotgun metagenomics, the functionality of the microbiome across three bee diet types: obligate pollinivory, obligate necrophagy, and facultative necrophagy. We find distinct differences in microbiome composition and gene functional profiles between the diet types. Obligate necrophages and pollinivores have more specialized microbes, whereas facultative necrophages have a diversity of environmental microbes associated with several dietary niches. Our study suggests that necrophagous bee microbiomes may have evolved to overcome cellular stress and microbial competition associated with carrion. We hypothesize that the microbiome evolved social phenotypes, such as biofilms, that protect the bees from opportunistic pathogens present on carcasses, allowing them to overcome novel nutritional challenges. Whether specific microbes enabled diet shifts or diet shifts occurred first and microbial evolution followed requires further research to disentangle. Nonetheless, we find that necrophagous microbiomes, vertebrate and invertebrate alike, have functional commonalities regardless of their taxonomy.

Comparison of seasonal viral prevalence supports honey bees as potential spring pathogen reservoirs for bumble bees

AbstractBee declines pose a serious risk to agricultural sustainability, wild plant diversity, and the commercial bee industry, generating local and global concerns about bee health. Parasites, including micro‐parasites and macro‐parasites, negatively impact bee population dynamics. Management of parasites requires an understanding of the cyclic trends in prevalence and the factors impacting these patterns. In this study, we advance understanding of parasite epidemiology and transmission among members of the bee community toward the goal of improving predictability of parasite prevalence seasonally. Honey bees and bumble bees were collected throughout an active season and across multiple overwintering periods. These bees were molecularly tested for two common bee viruses—deformed wing virus (DWV) and black queen cell virus (BQCV)—and morphologically screened for Vairimorpha spp., nematodes, and parasitic flies to determine whether these parasites exhibit unique seasonal trends, if overwintering behavior impacts parasite survival, and how these patterns differ between honey bees and bumble bees. The results suggest consistent seasonal trends between honey bees and bumble bees; however, these trends are parasite‐specific. Honey bees consistently exhibited a higher magnitude of viral prevalence compared with bumble bees. Both honey bees and bumble bees reduced viral prevalence over the winter; however, only in bumble bees did this drop to negligible prevalence each spring. These data suggest that honey bees may have a larger impact on parasite transmission, as they pose to reinfect bees which otherwise would have very low prevalence each spring and sustain high levels of infection in communities year‐round.

Bumble bee responses to climate and landscapes: Investigating habitat associations and species assemblages across geographic regions in the United States of America.

Bumble bees are integral pollinators of native and cultivated plant communities, but species are undergoing significant changes in range and abundance on a global scale. Climate change and land cover alteration are key drivers in pollinator declines; however, limited research has evaluated the cumulative effects of these factors on bumble bee assemblages. This study tests bumble bee assemblage (calculated as richness and abundance) responses to climate and land use by modeling species-specific habitat requirements, and assemblage-level responses across geographic regions. We integrated species richness, abundance, and distribution data for 18 bumble bee species with site-specific bioclimatic, landscape composition, and landscape configuration data to evaluate the effects of multiple environmental stressors on bumble bee assemblages throughout 433 agricultural fields in Florida, Indiana, Kansas, Kentucky, Maryland, South Carolina, Utah, Virginia, and West Virginia from 2018 to 2020. Distinct east versus west groupings emerged when evaluating species-specific habitat associations, prompting a detailed evaluation of bumble bee assemblages by geographic region. Maximum temperature of warmest month and precipitation of driest month had a positive impact on bumble bee assemblages in the Corn Belt/Appalachian/northeast, southeast, and northern plains regions, but a negative impact on the mountain region. Further, forest land cover surrounding agricultural fields was highlighted as supporting more rich and abundant bumble bee assemblages. Overall, climate and land use combine to drive bumble bee assemblages, but how those processes operate is idiosyncratic and spatially contingent across regions. From these findings, we suggested regionally specific management practices to best support rich and abundant bumble bee assemblages in agroecosystems. Results from this study contribute to a better understanding of climate and landscape factors affecting bumble bees and their habitats throughout the United States.

Evaluating Pollination and Weed Control Strategies under Mesotunnel Systems for Organic Muskmelon Production in Iowa

Bacterial wilt of cucurbits, caused by Erwinia tracheiphila, is spread by spotted (Diabrotica undeimpunctata howardi) and striped (Acalymma vittatum) cucumber beetles and results in major losses for US cucurbit (Cucurbitaceae spp.) growers. Organic growers of muskmelon (Cucumis melo) lack reliable control measures against bacterial wilt. During previous field trials in Iowa, USA, a system called mesotunnels, which are 3.5-ft-tall barriers covered with a nylon mesh insect netting, resulted in a higher marketable yield of organic ‘Athena’ muskmelon than low tunnels or noncovered plots. However, satisfactory pollination and weed control are challenging in mesotunnels because the netting covers the crop for most or all of the growing season, and economic feasibility of these systems has not been determined. Consequently, two field trials conducted in Iowa from 2020 to 2022 evaluated strategies to ensure pollination under mesotunnels in commercial-scale plots, assess effectiveness of teff (Eragrostis tef) as a living mulch for weed control in mesotunnel systems, and compare the profitability of the treatment options for organic ‘Athena’ muskmelon. The treatments used during the pollination trial were as follows: full season, in which mesotunnels remained sealed all season and bumble bees (Bombus impatiens) were added at the start of bloom for pollination; open ends, wherein both ends of the tunnels were opened at the start of bloom then reclosed 2 weeks later; and on-off-on, in which nets were removed at the start of bloom and then reinstalled 2 weeks later. The full-season treatment had significantly higher marketable yield than the other treatments in two of three trial years. Plants with the full season and open ends treatments had a bacterial wilt incidence <2.5% across all three years and similar numbers of cucumber beetles, whereas plants with the on-off-on treatment had an average bacterial wilt incidence of 11.0% and significantly more cucumber beetles. The open ends treatment had fewer bee visits to ‘Athena’ muskmelon flowers than the other treatments. In the 2-year (2021–22) weed management trial, treatments applied to the furrow between plastic-mulched rows were as follows: landscape fabric; teff seeded at 4 lb/acre and mowed 3 weeks after seeding; teff seeded at 4 lb/acre and not mowed; a control with bare ground where weeds were mowed 3 weeks after transplanting; and a bare ground control with no mowing. The landscape fabric and mowed teff treatments had statistically similar marketable yield, and mowing appeared to minimize yield losses compared with nonmowed treatments. The landscape fabric had no weeds, followed by mowed teff, mowed bare ground, and nonmowed teff. Nonmowed bare ground had the highest weed biomass. The partial budget and cost-efficiency ratio analysis indicated that the full-season treatment was the most cost-efficient pollination option for mesotunnel systems. An economic analysis of the weed management strategies showed that using teff as a living mulch in the furrows between organic ‘Athena’ muskmelon rows, coupled with timely mowing to suppress its growth, can generate revenue comparable to that of landscape fabric. Our findings suggest that organic ‘Athena’ muskmelon growers in Iowa may gain the greatest yield and soil quality benefits when mesotunnels are kept closed for the entire season, bumble bees are used for pollination, and teff (mowed 3 weeks after seeding) is used to control weeds in the furrows. Further trials integrating these pollination and weed management strategies would help validate a comprehensive approach to organic ‘Athena’ muskmelon production under mesotunnels.

Deep learning for identifying bee species from images of wings and pinned specimens.

One of the most challenging aspects of bee ecology and conservation is species-level identification, which is costly, time consuming, and requires taxonomic expertise. Recent advances in the application of deep learning and computer vision have shown promise for identifying large bumble bee (Bombus) species. However, most bees, such as sweat bees in the genus Lasioglossum, are much smaller and can be difficult, even for trained taxonomists, to identify. For this reason, the great majority of bees are poorly represented in the crowdsourced image datasets often used to train computer vision models. But even larger bees, such as bumble bees from the B. vagans complex, can be difficult to separate morphologically. Using images of specimens from our research collections, we assessed how deep learning classification models perform on these more challenging taxa, qualitatively comparing models trained on images of whole pinned specimens or on images of bee forewings. The pinned specimen and wing image datasets represent 20 and 18 species from 6 and 4 genera, respectively, and were used to train the EfficientNetV2L convolutional neural network. Mean test precision was 94.9% and 98.1% for pinned and wing images respectively. Results show that computer vision holds great promise for classifying smaller, more difficult to identify bees that are poorly represented in crowdsourced datasets. Images from research and museum collections will be valuable for expanding classification models to include additional species, which will be essential for large scale conservation monitoring efforts.

Pollinator planting establishment and bee visitation are influenced by seeding rate and post‐seeding management

Perennial wildflower plantings are commonly used to support pollinators and other beneficial insects, but their establishment can be costly, and few studies have directly compared the effectiveness of different management strategies for wildflower establishment. To determine the relative importance of pre‐seeding weed control, seed density, and post‐seeding management on seed mix establishment, we developed a multifactorial field experiment in a grass‐dominated weed community. Pre‐seeding management treatments (mowing, herbicide, or soybean cover crops) did not affect the stem density of sown plants, or the percent of ground covered by sown plants. However, the percent of ground covered by weeds was significantly influenced by pre‐seeding treatments, with infrequent mowing resulting in significantly less weedy ground cover than the herbicide or soybean pre‐seeding treatments. Plots with a higher seeding rate had a significantly greater density of sown wildflower species and a higher percent cover of these species after 3 years. Plots that received no post‐seeding management had higher stem density, a greater percent ground cover of sown forbs, and higher species richness compared to those that were intensively managed (mow or mow + herbicide). The total number of bee visits (honey bees, bumble bees, and other wild bees) increased with higher forb species richness, higher ground cover of sown forbs, and higher sown species richness. Doubling the density of seeds resulted in a 24.3% increase in the number of wild bees observed. When establishing wildflower habitat for pollinators, investment in ground preparation and seeding density has the greatest impact on sown species establishment.

Determining the plant-pollinator network in a culturally significant food and medicine garden in the Great Lakes region.

Understanding the interactions between plants and pollinators within a system can provide information about pollination requirements and the degree to which species contribute to floral reproductive success. Past research has focused largely on interactions within monocultured agricultural systems and only somewhat on wild pollination networks. This study focuses on the culturally significant Three Sisters Garden, which has been grown and tended by many Indigenous peoples for generations in the Great Lakes Region. Here, the plant-pollinator network of the traditional Three Sisters Garden with the inclusion of some additional culturally significant plants was mapped. Important visitors in this system included the common eastern bumble bee, Bombus impatiens Cresson (Hymenoptera: Apidae), and the hoary squash bee, Xenoglossa pruinosa (Say) (Hymenoptera: Apidae), as determined by their abundances and pollinator service index (PSI) values. Understanding the key pollinators in the Three Sisters Garden links biological diversity to cultural diversity through the pollination of culturally significant plants. Further, this information could be of use in supporting Indigenous food sovereignty by providing knowledge about which wild pollinators could be supported to increase fruit and seed set within the Three Sisters Garden. Our findings can also lead to more effective conservation of important wild pollinator species.

Genetic modification of the bee parasite Crithidia bombi for improved visualization and protein localization

Crithidia bombi is a trypanosomatid parasite that infects several species of bumble bees (Bombus spp.), by adhering to their intestinal tract. Crithidia bombi infection impairs learning and reduces survival of workers and the fitness of overwintering queens. Although there is extensive research on the ecology of this host-pathogen system, we understand far less about the mechanisms that mediate internal infection dynamics. Crithidia bombi infects hosts by attaching to the hindgut via the flagellum, and one previous study found that a nectar secondary compound removed the flagellum, preventing attachment. However, approaches that allow more detailed observation of parasite attachment and growth would allow us to better understand factors mediating this host-pathogen relationship. We established techniques for genetic manipulation and visualization of cultured C. bombi. Using constructs established for Crithidia fasciculata, we successfully generated C. bombi cells expressing ectopic fluorescent transgenes using two different selectable markers. To our knowledge, this is the first genetic modification of this species. We also introduced constructs that label the mitochondrion and nucleus of the parasite, showing that subcellular targeting signals can function across parasite species to highlight specific organelles. Finally, we visualized fluorescently tagged parasites in vitro in both their swimming and attached forms, and in vivo in bumble bee (Bombus impatiens) hosts. Expanding our cell and molecular toolkit for C. bombi will help us better understand how factors such as host diet, immune system, and physiology mediate outcomes of infection by these common parasites.

Evaluation of the most popular annual flowers sold in the United States and Europe indicates low visitation rates by pollinators and large variation among cultivars.

To better understand how frequently pollinators visit the most popular annuals and the variation among cultivars, we evaluated 3-6 cultivars, each of petunia, impatiens, begonia, geranium, pansy, and New Guinea impatiens. These 6 annuals account for 46.6% of all garden center annual flower sales in the United States. Flower visits by honey bees, bumble bees, syrphids, other Diptera and other Hymenoptera, combined, varied 3 to 10-fold among cultivars within each of the 6 popular annuals. Begonia and impatiens were visited more frequently by pollinators than pansy, petunia, NG impatiens, and geranium. The 4 most visited cultivars, begonia 'Cocktail Brandy', begonia 'Ambassador Rose Blush', impatiens 'Accent Coral', and impatiens 'Super Elfin XP White' attracted as many pollinators as a benchmark annual, marigold 'Alumia Vanilla Cream', considered as moderately attractive to pollinators. Some conclusions from this research may be helpful for homeowners, landscapers, growers, and breeders. First, the most popular annual flowers are not a good choice for the purpose of attracting and supporting pollinators. However, the large variation among cultivars provides an opportunity to select cultivars that are more attractive to pollinators, particularly for begonia and impatiens. If the most pollinator-visited cultivars of begonia and impatiens are labeled and promoted as such, it would be beneficial to pollinators in urban and suburban landscapes in the USA and Europe, where they comprise 10%-20% of all annual flowers purchased from garden centers.

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.

Bumble bee diet breadth increases with local abundance and phenophase duration, not intraspecific variation in body size

Patterns of abundance across space and time, and intraspecific variation in body size, are two species attributes known to influence diet breadth and the structure of interaction networks. Yet, the relative influence of these attributes on diet breadth is often assumed to be equal among taxonomic groups, and the relationship between intraspecific variation in body size on interaction patterns is frequently neglected. We observed bee–flower interactions in multiple locations across Montana, USA, for two growing seasons and measured spatial and temporal patterns of abundance, along with interspecific and intraspecific variation in body size for prevalent species. We predicted that the association between spatial and temporal patterns of abundance and intraspecific variation in body size, and diet breadth, would be stronger for bumble bee compared to non-bumble bee species, because species with flexible diets and long activity periods can interact with more food items. Bumble bees had higher local abundance, occurred in many local communities, more intraspecific variation in body size, and longer phenophases compared to non-bumble bee species, but only local abundance and phenophase duration had a stronger positive association with the diet breadth of bumble bee compared to non-bumble bee species. Communities with a higher proportion of bumble bees also had higher intraspecific variation in body size at the network-level, and network-level intraspecific variation in body size was positively correlated with diet generalization. Our findings highlight that the association between species attributes and diet breadth changes depending on the taxonomic group, with implications for the structure of interaction networks.

Leveraging virtual datasets to investigate the interplay of pollinators, protected areas, and SDG 15

Biodiversity loss amplifies the need for taxonomic understanding at global, regional, and local scales. The United Nations Environmental Programme Sustainable Development Goals are explicit in their demand for greater accountability with respect to ecosystem management, and Sustainable Development Goal 15, Life on Land, specifically calls for a halt to biodiversity loss. Pollinators (bees and butterflies) are two functional groups with public attention for protection, yet little long-term data availability. National Parks, including those in the United States, act as optimal sites to study biodiversity loss, but historic data tends to vary in availability. This study addresses systematic taxonomic and digitalization biases present within historic (museum), modern (citizen science), and non-digitized (private collection) datasets for Yellowstone and Grand Teton National Parks from 1900 to 2021. We find that, although database record availability is representative of butterfly and bumble bee groups known for the area, categories such as data rescue, digitalization/availability, and management/archiving vary across database types. These findings on virtual datasets offer opportunities for conservationists to understand the efficacy of digitized collections in addressing questions of species loss over time, including the strengths and pitfalls of digitized data repositories. Additionally, virtual datasets can be utilized to monitor biodiversity under Sustainable Development Goal 15 targets while also promoting broader access to resources such as museum collections for educational purposes.

A rapid return to normal: temporal gene expression patterns following cold exposure in the bumble bee Bombus impatiens.

Bumble bees are common in cooler climates and many species likely experience periodic exposure to very cold temperatures, but little is known about the temporal dynamics of cold response mechanisms following chill exposure, especially how persistent effects of cold exposure may facilitate tolerance of future events. To investigate molecular processes involved in the temporal response by bumble bees to acute cold exposure, we compared mRNA transcript abundance in Bombus impatiens workers exposed to 0°C for 75 min (inducing chill coma) and control bees maintained at a constant ambient temperature (28°C). We sequenced the 3' end of mRNA transcripts (TagSeq) to quantify gene expression in thoracic tissue of bees at several time points (0, 10, 30, 120 and 720 min) following cold exposure. Significant differences from control bees were only detectable within 30 min after the treatment, with most occurring at the 10min recovery time point. Genes associated with gluconeogenesis and glycolysis were most notably upregulated, while genes related to lipid and purine metabolism were downregulated. The observed patterns of expression indicate a rapid recovery after chill coma, suggesting an acute differential transcriptional response during recovery from chill coma and return to baseline expression levels within an hour, with no long-term gene expression markers of this cold exposure. Our work highlights the functions and pathways important for acute cold recovery, provides an estimated time frame for recovery from cold exposure in bumble bees, and suggests that cold hardening may be less important for these heterothermic insects.

ECR Spotlight – Kelton Verble and Ellen Keaveny

ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Kelton Verble and Ellen Keaveny are authors on ‘A rapid return to normal: temporal gene expression patterns following cold exposure in the bumble bee Bombus impatiens’, published in JEB. Kelton is a PhD candidate in the lab of Dr Jeffrey Lozier at The University of Alabama, USA, investigating the transcriptomics and epigenomics underlying thermal tolerance in bumble bees. Ellen is a PhD candidate in the lab of Michael Dillon at the University of Wyoming, USA, investigating how temperature affects bumble bees at cellular, organismal, population and community levels.