More efficient environmental risk assessment and stronger protection are achievable.

Nutritional ecology is a key determinant of bee health, yet species-specific preferences and how bees respond nutritionally to real-world pesticide exposure remain unclear. We collected pollen stores from three managed bee species in 128 sites across two widespread agro-ecosystems (i.e., oilseed rape fields and apple orchards) in eight European countries. We measured protein content, lipid content, protein-to-lipid ratio as well as pesticide residues in pollen stores. We provide the first evidence of species-specific macronutritional patterns in the pollen stores of three managed bee species. The buff-tailed bumble bee stored pollen with significantly lower lipid content (mean: 44.1 mu g/mg) than the European honey bee (mean: 57.2 mu g/mg) and the red mason bee (mean: 54 mu g/mg). This reduced lipid content translated into a higher protein-to-lipid (P:L) ratio in the buff-tailed bumble bee (mean: 8.53) when compared to the European honey bee (mean: 5.85) and the red mason bee (mean: 5.60). Pesticide risk, measured as toxicity-weighted concentrations in pollen stores, did not influence P:L ratios in any species. However, increasing pesticide risk was associated with reduced protein content and lipid content in buff-tailed bumble bee stores, potentially leading to suboptimal colony development, whereas it was associated with increased protein content in red mason bee stores. Our findings suggest that bees maintain consistent macronutritional profiles in their pollen stores under pesticide exposure, at least in terms of P:L ratios, suggesting limited capacity to adapt their macronutritional dietary choices to mitigate agrochemical stress. These findings highlight a critical need to balance floral enhancements with a reduction in pesticide use to safeguard pollinators in agricultural landscapes.

Trace elements are persistent contaminants that enter bee diets through pollen, nectar, soil-derived particles and atmospheric deposition, yet field-based exposure data for pollinator taxa remain limited. We examined 18 trace elements (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Se, U, V, Zn) in pollen stored by managed western honey bees (Apis mellifera), buff-tailed bumble bees (Bombus terrestris), and red mason bees (Osmia bicornis) from 128 apple orchards and oilseed rape fields across eight European countries. We assessed species-, crop- and landscape-related drivers of element accumulation in stored pollen and honey bee workers, and used these data to estimate dietary exposure and risk. Stored pollen showed crop- and species-specific differences in trace element levels. Red mason bee pollen contained several-fold higher concentrations than honey bee and bumble bee pollen, suggesting that honey bees may not be a suitable model for pollen-based exposure studies. Stored pollen from apple orchards contained higher Cu than that from oilseed rape sites, likely linked to Cu-based fungicide use. Landscape characteristics, including crop and urban cover, influenced element concentrations in stored pollen and honey bee workers. Acute risks were assessed for As, Cd, Cu, and Hg, and chronic risks for As and Cd. For elements with available toxicity endpoints, estimated dietary risk was negligible or low; for elements lacking such endpoints, risk could not be quantified despite exposure estimates. Higher exposure of solitary bees, together with scarce toxicity data, indicates that future studies should focus on establishing species-specific toxicity endpoints.

Background Wild pollinator populations in the European Union lack defined, quantitative Specific Protection Goals (SPGs) for pesticide risk assessment. Without an agreed threshold, lower-tier toxicity data cannot be evaluated for acceptability, nor can higher-tier study results be assessed against a protection goal, leaving the tiered ERA process at an impasse. The existing honey bee surrogate compounds the problem: this was selected for laboratory convenience rather than functional representativeness, and their managed, colonial life history cannot reliably predict outcomes for the diverse life-history strategies of wild pollinators. Results This paper presents a pragmatic, staged framework combining trait-based species selection with demographic toxicity assessment. It focuses on Stage 1 (non-spatial) of a the three-stage process, where life-stage-structured population models are implementable now (2026–2027), uses existing data and tools, and generates quantitative, population-level SPG thresholds within the current [1] tiered assessment framework. The framework combines two methodological advances: trait-based species selection identifies functionally vulnerable species by grouping taxa according to exposure- and sensitivity-related traits and population resilience; and demographic toxicity assessment translates individual-level pesticide effects into population-level outcomes through life-stage-structured projection matrices. Parameter space exploration demonstrates that Stage 1 yields defined, quantitative thresholds: a maximum acceptable population decline and a maximum acceptable exceedance risk probability. Conclusions Stage 1 resolves the immediate operational constraint by providing provisional, population-level thresholds for regulatory use. A roadmap for adaptive implementation and progressive refinement is provided: Stage 2 (operational 2028–2029) incorporates landscape-scale spatial dynamics, and Stage 3 (operational 2030+) implements full agent-based modelling using the ALMaSS system. The approach is demonstrated for bees (bumble bees and solitary bees), but the trait-based framework is designed to be flexible enough to generalise across hoverflies, butterflies, moths, and other pollinating taxa.

Wild insect pollinators contribute significantly to agricultural productivity, biodiversity, and ecosystem functioning. Wild pollinators are increasingly affected by multiple interacting stressors. Proactively identifying emerging risks and feasible mitigation strategies will be critical to ensuring the long-term stability of wild pollinators biodiversity and pollination services. We conducted the first continental scale horizon scan focused on wild pollinators in Europe. A structured Delphi-based approach was used to identify emerging issues that may have significant implications for wild pollinators over the coming decade. Ten priority issues were identified, including both potential risks and opportunities. For the first time in a pollinator-focused horizon scan, legislation was identified as a key opportunity, with the European Union Nature Restoration Regulation recognised for its potential to influence pollinator conservation through mandatory restoration and monitoring targets. In contrast, political developments such as the rise of populist parties and post-truth discourse may impede policy implementation. Several issues relating to pesticide use were also identified, including developments in RNA interference technologies and precision application methods, which may reduce non-target impacts if risks are appropriately assessed. These findings provide a foundation for further research and policy evaluation in support of pollinator conservation under changing environmental and political conditions.

The ecological impact of Bombus terrestris (Linnaeus, 1758) (Hymenoptera: Apidae) following its introduction to regions outside its native range has raised significant concerns, particularly regarding the decline of native pollinators. Male B. terrestris secrete pheromones that are used in reproductive communication, and which have the potential to be used as trap attractants to control invasive populations. However, while gynes (virgin reproductive females) are known to be attracted to these pheromones, nothing is known about behavioral responses of male B. terrestris to them. Here, we investigated whether male B. terrestris exhibit attraction to pheromone extracts from conspecific males under controlled laboratory conditions. A Y-tube olfactometer was used to present B. terrestris males with a choice between a pheromone extract and a control treatment. Males were shown to respond to a positive control of lavender oil; however, they exhibited no attraction to the pheromone extracts. Several factors, such as pheromone concentration, age of individuals, or apparatus design, may have influenced these results. These findings contribute to our knowledge of bumblebee chemical communication and may inform future experimental design to assess pheromone attraction in bumblebees.

Insect pollinators are currently declining, in part due to the loss of habitats and foraging resources. However, one potential source of refuge is lawns in urban areas and the floral resources within them. Lawns represent a substantial proportion of urban green space and, if managed with pollinators in mind, could become a major component of a matrix of foraging resources. This study used Ministry of Justice prison and court sites as a case study for the management of urban lawn space. Sites contained four patches, one control patch mown as normal every two weeks and then three patches mown either every four, six or 12 weeks. Weekly pollinator and flowering plant surveys were completed at each site over 12 weeks from June – August 2023. We found that patches with less frequent mowing (every six and 12 weeks) had a significantly higher abundance of pollinators, >170% higher than the typically used mowing frequency of every two weeks. Lawns left unmown for 12 weeks also had higher floral species richness and flower cover than lawns mown every two weeks. Consequently, we recommend that lawns within urban and suburban building complexes are mown at an interval of at least six, but ideally 12, weeks to improve floral resources and pollinator abundance.

Climate can vary spatially and temporally and is becoming increasingly unpredictable due to climate change. It can have a large impact on host-parasite interactions and investigating this effect is vital both for understanding current parasite distribution and epidemiology, and predicting how this will change in the future. Here, we conducted a meta-analysis to determine whether temperature and precipitation have an overall effect on parasite prevalence and infection intensity in terrestrial animals. This is a phylogenetically controlled quantitative synthesis to assess parasite prevalence and infection intensity in terrestrial animals across contrasting temperatures and precipitation. We found large variation in the effect of temperature on parasite prevalence, precipitation on parasite prevalence, and temperature on infection intensity. This provides robust quantitative evidence against the controversial "warmer sicker world" hypothesis. There was no effect of climate on parasitism, irrespective of whether the parasite was an endoparasite or ectoparasite, or across different parasite lifecycles. Although some host and parasite taxa were understudied, we found no consistent taxonomic patterns. Importantly, we revealed large gaps in the literature, including the relationship between humidity, prevalence, and infection intensity. Ectoparasites and reptile hosts were also very underrepresented, and deserve further study. Focusing future research on these gaps will help to confirm whether certain types of host-parasite interactions are more or less sensitive to changes in climate, with implications for conservation.

The composition of viral communities (i.e. viromes) can be dynamic and complex. Co-evolution may lead to virome host-specificity. However, eco-evolutionary factors may influence virome dynamics in wild host communities, potentially leading to disease emergence. Social bees are relevant models to address the drivers of virome composition: these important pollinators form multi-species assemblages, with high niche overlap and strong seasonality in their biotic interactions. We applied a microbial community approach to disentangle the role of host phylogeny and host ecology in shaping bee viromes, combining plant-pollinator networks with meta-transcriptomics, and small interfering RNAs as proxies for viral replication in pollinators and pollen. We identified over a hundred insect and plant viral sequences from ca. 4500 insect pollinator samples across three time points in one year. While host genetic distance drives the distribution of bee viruses, we find that plant-pollinator interactions and phenology drive plant virus communities collected by bees. This reveals the opportunities for virus spread in the bee assemblage. However, we show that transmission to multiple hosts is only realized for a fraction of insect viruses, with even fewer found to be actively replicating in multiple species, including the particularly virulent multi-host acute bee paralysis virus.

Parasitoid wasps are a large group of species-rich superfamilies within the order Hymenoptera which form an essential part of terrestrial ecosystems. Many species hold additional value as natural enemies of agricultural pests. Considering their ecological and economic importance, it is perhaps surprising that a significant proportion of these insects are understudied. Here we focus on one genus of parasitoid wasp, Syntretus, due to its parasitism of short-haired bumblebee (Bombus subterraneus) queens from Sweden, investigated as part of a reintroduction programme in the United Kingdom (UK). We used a genome-skimming approach to recover mitochondrial and nuclear DNA from single legs of Syntretus museum specimens, to elucidate the metagenomic content of archival samples and assess their suitability for use in phylogenetic analysis. Utilising 6.7 kb of genomic DNA, we recovered two clades within Syntretus, a possible consequence of host choice. Our analyses also recovered commensal polydnavirus sequences, which is the first time this endogenous virus has been identified in this parasitoid genus. These commensal virions are likely used by egg-laying female Syntretus to circumnavigate host immune responses so that larvae can develop. Our polydnavirus Bayesian phylogeny suggests that the viral genomes may have different evolutionary histories to their Syntretus hosts, which we infer from the lack of support for co-speciation in this symbiosis. Finally, we elucidate a novel host-parasitoid relationship by identifying that S. politus parasitises B. subterraneus in Sweden. Combined, our results demonstrate the value of museum collections in undertaking detailed host-parasitoid studies, which can, in turn, inform conservation strategies.

Pesticide use and habitat loss are major anthropogenic drivers of bee decline, raising global concerns about impaired crop pollination. However, the relative importance of these stressors and their combined impact on bee assemblages comprising species with different traits, such as body size or nesting strategy, remains unknown. Here we addressed these key knowledge gaps in a global quantitative synthesis analysing bee assemblage data from 681 crop fields across three continents. We found that both local pesticide hazards and decreasing proportions of semi-natural habitats in surrounding landscapes negatively affected wild bee abundance and species richness in crop fields, while pesticides additionally reduced functional and phylogenetic diversity. Semi-natural habitat availability did not buffer against these negative pesticide effects, nor did we identify any specific traits rending bees more vulnerable to one of the two drivers. Our findings highlight the pressing need to reduce non-target effects of pesticide use and emphasize that conservation and restoration of semi-natural habitats successfully promote wild bees, but are insufficient strategies to mitigate pesticide-driven losses of wild bee pollinators from crop fields.

Disease and habitat loss are significant causes of pollinator declines, and evidence indicates the two are linked. In Britain, lowland heath is an important bee habitat, but over 80% has been lost since the 1800s. This deprives wild bees of a rich food resource, but also the health benefits of an antimicrobial metabolite from Calluna vulgaris nectar, callunene, which reduces infection by the gut parasite Crithidia bombi in individual bumblebees. Here, we test whether these individual impacts can control epidemics in social colonies. We inoculated workers in early-stage Bombus terrestris colonies with Cr. bombi and randomly assigned colonies to the following treatments: (i) heather extract, (ii) callunene, and (iii) a sugar-water control. Colony infection rates were measured weekly. Colonies that were exposed to heather metabolites or callunene had a lower prevalence of Cr. bombi, especially the flagellated, infectious form, when compared to controls. Consequently, we conclude that these antimicrobial metabolites can control epidemics in social bumblebees. This suggests that lowland heaths may act not just as an important food source but as an essential natural pharmacy for pollinators.

Metal pollution poses a growing threat to wildlife, including bees, which play a crucial role in pollination. While the toxic effects of metals on bees are well documented, their ability to avoid contaminated food sources, and whether this behaviour is shaped by social context, remains unclear. Using the buff-tailed bumble bee and two metals, copper (i.e. essential metal) and cadmium (i.e. non-essential metal), we first assessed workers' avoidance of metal-laced 50% sucrose solutions when given the choice of an uncontaminated alternative. We introduced an energetic trade-off situation by reducing sucrose concentration to 20% in the untreated solution. Finally, to test the influence of brood care, workers were kept either with or without larval siblings. When both treated and untreated solutions contained 50% sucrose, workers consistently avoided the metal-contaminated solution, regardless of brood presence. However, when sucrose concentration was reduced in the uncontaminated solution, workers preferred the contaminated option, but only in the absence of brood. In the presence of brood, workers favoured the metal-free but sucrose-poor solution, suggesting adaptive provisioning behaviour to protect larvae. This study provides the first evidence that bumble bee workers not only actively avoid metal-contaminated solutions but also adjust foraging strategies based on social context.

Abstract Bees are key pollinators, and thus declines in their populations around the world may lead to negative consequences for both the environment and agricultural systems. While these declines are caused by multiple factors, the use of pesticides in agricultural systems has been identified as a key potential driver. Most bee species have an annual life cycle, with the potential for pesticide exposure throughout their life span. However, most studies have looked at a single exposure point within a season. Bumblebees, like most annual species, have an overwintering stage—which in their case is completed by bumblebee queens. Exposure to pesticides can be experienced by queens both before and after physiologically stressful periods such as hibernation and during nest foundation. This multi‐staged exposure may have increased impacts on bumblebee queens' colony foundation and reproductive output and therefore colony success. However, studies of such repeated exposures are lacking. Here, we look at the effects of an unstudied, yet biologically likely exposure regime. We exposed bumblebee queens to the insecticide sulfoxaflor at 65.5 ppb for 4 days both before and after hibernation, using a fullycrossed design, in order to assess the impact of such repeated exposure on survival and reproductive fitness. We observed queens through two important life stages, hibernation and colony foundation, following field realistic exposures to sulfoxaflor. We measured the effects on hibernation success, the likelihood of colony foundation and brood production. We found that neither exposure to sulfoxaflor pre‐ or post‐hibernation, nor their combination, impacted hibernation survival or colony foundation. Practical Implication: Our study is the first to highlight the repeated pesticide exposure bumblebee queens experience over different stages of their life cycle. Our results suggest that single or repeated exposure to dietary sulfoxaflor alone, albeit at a conservative field‐realistic profile, is unlikely to impact queen health at key points in their life cycle. Future studies should explicitly incorporate repeated exposure across life cycle stages when assessing the impacts of anthropogenic stressors on bee health.

One factor that can affect infection susceptibility is host age, the effects of which vary in a range of ways. For example, susceptibility may increase with age, due to senescence or decrease with age as a result of maturation of the immune system. If certain ages are more susceptible to infection, populations with contrasting demographics, such as same-age cohorts versus a mixture of ages, will exhibit differing disease prevalence. We use the bumblebee, Bombus terrestris , and its interaction with the gut trypanosome Crithidia sp. as a model system to investigate age-related susceptibility in a social insect. Crithidia sp. are widespread and prevalent parasites of bumblebees that are spread between colonies via faeces on flowers when foraging, and within colonies via contact with infected bees and contaminated surfaces and resources. In the field, Bombus spp. live for approximately three weeks. Here, we inoculated bumblebees at 0, 7, 14 and 21 days of age and measured their infection after one week. We also measured the level of gene expression of two antimicrobial peptides important in the defence against Crithidia bombi in bumblebees. We found that younger bumblebees are more susceptible to infection by Crithidia sp. than their older siblings. Specifically, individuals inoculated on their first day of emergence had infection intensities seven days later that were four-fold higher than bees inoculated at 21 days of age. In contrast, the gene expression of two AMPs known to protect against the trypanosome, abaecin and defensin, did not significantly vary with age. These results suggest that age does affect susceptibility to Crithidia sp. infection in B. terrestris. The higher susceptibility of callows may have implications for the susceptibility of colonies at different stages of their lifecycle, due to the contrasting age demography of workers in the colony.

Pollinators are vital for food security and the maintenance of terrestrial ecosystems. Bumblebees are important pollinators across northern temperate, arctic, and alpine ecosystems, yet are in decline across the globe. Vairimorpha bombi is a parasite belonging to the fungal class Microsporidia that has been implicated in the rapid decline of bumblebees in North America, where it may be an emerging infectious disease. To investigate the evolutionary basis of pathogenicity of V. bombi, we sequenced and assembled its genome using Oxford Nanopore and Illumina technologies and performed phylogenetic and genomic evolutionary analyses. The genome assembly for V. bombi is 4.73 Mb, from which we predicted 1,870 protein-coding genes and 179 tRNA genes. The genome assembly has low repetitive content and low GC content. V. bombi's genome assembly is the smallest of the Vairimorpha and closely related Nosema genera, but larger than those found in the Encephalitozoon and Ordospora sister clades. Orthology and phylogenetic analysis revealed 18 core conserved single-copy microsporidian genes including the histone acetyltransferase (HAT) GCN5. Surprisingly, V. bombi was unique to the microsporidia in not encoding the second predicted HAT ESA1. The V. bombi genome assembly annotation included 265 unique genes (i.e. not predicted in other microsporidia genome assemblies), 20% of which encode a secretion signal, which is a significant enrichment. Intriguingly, of the 36 microsporidian genomes we analyzed, 26 also had a significant enrichment of secreted signals encoded by unique genes, ranging from 6 to 71% of those predicted genes. These results suggest that microsporidia are under selection to generate and purge diverse and unique genes encoding secreted proteins, potentially contributing to or facilitating infection of their diverse hosts. Furthermore, V. bombi has 5/7 conserved spore wall proteins (SWPs) with its closest relative V. ceranae (that primarily infects honeybees), while also uniquely encoding four additional SWPs. This gene class is thought to be essential for infection, providing both environmental protection and recognition and uptake into the host cell. Together, our results show that SWPs and unique genes encoding a secretion signal are rapidly evolving in the microsporidia, suggesting that they underpin key pathobiological traits including host specificity and pathogenicity.

Increasing evidence shows that wild bees, including bumble bees, are in decline due to a range of stressors, including pesticides. Our knowledge of pesticide impacts has consequently grown to enable the design of increasingly realistic risk assessment methods. However, one area where knowledge gaps may still hinder our ability to assess the full range of bee-pesticide interactions is the field of exposure. Exposure has historically been linked to either direct contact with pesticides or the ingestion of contaminated pollen and nectar by bees. However, bumble bees, and other wild bees, may also be exposed to pesticides while using contaminated soil as an overwintering substrate. Yet knowledge of how soil-mediated exposure affects bumble bee health is lacking. Here we take one of the first steps towards addressing this knowledge gap by designing a method for testing the effects of soil-mediated pesticide exposure on bumble bee queen hibernation success. We measured hibernation survival, body weight change and abdominal fat content and found that none of these responses were affected by a field realistic soil exposure to the novel insecticide cyantraniliprole. Our study may help in developing a standardised method to test the effects of the soil-mediated pesticide exposure route in bumble bee queens.

Infectious and parasitic agents (IPAs) and their associated diseases are major environmental stressors that jeopardize bee health, both alone and in interaction with other stressors. Their impact on pollinator communities can be assessed by studying multiple sentinel bee species. Here, we analysed the field exposure of three sentinel managed bee species (Apis mellifera, Bombus terrestris and Osmia bicornis) to 11 IPAs (six RNA viruses, two bacteria, three microsporidia). The sentinel bees were deployed at 128 sites in eight European countries adjacent to either oilseed rape fields or apple orchards during crop bloom. Adult bees of each species were sampled before their placement and after crop bloom. The IPAs were detected and quantified using a harmonised, high-throughput and semi-automatized qPCR workflow. We describe differences among bee species in IPA profiles (richness, diversity, detection frequencies, loads and their change upon field exposure, and exposure risk), with no clear patterns related to the country or focal crop. Our results suggest that the most frequent IPAs in adult bees are more appropriate for assessing the bees’ IPA exposure risk. We also report positive correlations of IPA loads supporting the potential IPA transmission among sentinels, suggesting careful consideration should be taken when introducing managed pollinators in ecologically sensitive environments.