Towards unbiased interpretations of interactive effects in ecotoxicological studies.

Ecotoxicological research has increasingly focused on the interactive effects of chemical mixtures on biological models, emphasising additive, synergistic, or antagonistic interactions. However, these combination studies often test chemicals at unique concentrations (e.g. x:y), limiting our understanding of the effects across the full spectrum of possible combinations. Evidence from human toxicology suggests that interactive effects among chemicals can vary significantly with total concentration (e.g. x:y vs. 2x:2y), their ratio (e.g. x:2y vs. 2x:y), and the magnitude of the tested effect (e.g. LC10vs. LC50). Our non-exhaustive review of studies on binary mixtures in bee ecotoxicology reveals that such parameters are frequently neglected. Of the 60 studies we examined, only two utilised multiple total concentrations and ratios, thus exploring a broad range of possible combinations. In contrast, 26 studies tested only a single concentration of each chemical, resulting in incomplete interpretations of the potential interactive effects. Other studies utilised various concentrations and/or ratios but failed to capture a broad spectrum of possible combinations. We also discuss potential discrepancies in interactive effects based on different metrics and exposure designs. We advocate for future ecotoxicological studies to investigate a wider spectrum of chemical combinations, including various concentrations and ratios, and to address different levels of effects.

A comparative genomic analysis of Fructobacillus evanidus sp. nov. from bumble bees.

The increase in studies on bee microbiomes is prompted by concerns over global pollinator declines. Bumble bees host core and non-core microbiota which may contribute to increased lifetime fitness. The presence of Fructobacillus in the gut microbiomes of bumble bee workers, or the replacement of core symbionts with Fructobacillus bacteria, has been considered a marker of dysbiosis. A phylogenomic analysis and functional genomic characterization of the genomes of 21 Fructobacillus isolates from bumble bees demonstrated that they represented four species, i.e. Fructobacillus cardui, Fructobacillus fructosus, Fructobacillus tropaeoli, and the novel species Fructobacillus evanidus sp. nov. Our results confirmed and substantiated the presence of two phylogenetically and functionally distinct Fructobacillus species clades that differ in genome size, percentage G + C content, the number of coding DNA sequences and metabolic characteristics. Clade 1 and clade 2 species differed in amino acid and, to a lesser extent, in carbohydrate metabolism, with F. evanidus and F. tropaeoli genomes featuring a higher number of complete metabolic pathways. While Fructobacillus genomes encoded genes that allow adhesion, biofilm formation, antibacterial activity and detoxification, other bacteria isolated from the bumble bee gut appeared better equipped to co-exist with the bumble bee host. The isolation and identification of multiple Fructobacillus species from several bumble bee gut samples in the present study also argued against a specific partnership between Fructobacillus species and their bumble bee hosts.

A new exposure protocol adapted for wild bees reveals species-specific impacts of the sulfoximine insecticide sulfoxaflor.

Wild bees are crucial pollinators of flowering plants and concerns are rising about their decline associated with pesticide use. Interspecific variation in wild bee response to pesticide exposure is expected to be related to variation in their morphology, physiology, and ecology, though there are still important knowledge gaps in its understanding. Pesticide risk assessments have largely focussed on the Western honey bee sensitivity considering it protective enough for wild bees. Recently, guidelines for Bombus terrestris and Osmia bicornis testing have been developed but are not yet implemented at a global scale in pesticide risk assessments. Here, we developed and tested a new simplified method of pesticide exposure on wild bee species collected from the field in Belgium. Enough specimens of nine species survived in a laboratory setting and were exposed to oral and topical acute doses of a sulfoximine insecticide. Our results confirm significant variability among wild bee species. We show that Osmia cornuta is more sensitive to sulfoxaflor than B. terrestris, whereas Bombus hypnorum is less sensitive. We propose hypotheses on the mechanisms explaining interspecific variations in sensitivity to pesticides. Future pesticide risk assessments of wild bees will require further refinement of protocols for their controlled housing and exposure.

The InBIO Barcoding Initiative Database: DNA barcodes of Iberian Bees.

Background: Bees are important actors in terrestrial ecosystems and are recognised for their prominent role as pollinators. In the Iberian Peninsula, approximately 1,100 bee species are known, with nearly 100 of these species being endemic to the Peninsula. A reference collection of DNA barcodes, based on morphologically identified bee specimens, representing 514 Iberian species, was constructed. The "InBIO Barcoding Initiative Database: DNA Barcodes of Iberian bees" dataset contains records of 1,059 sequenced specimens. The species of this dataset correspond to about 47% of Iberian bee species diversity and 21% of endemic species diversity. For peninsular Portugal only, the corresponding coverage is 71% and 50%. Specimens were collected between 2014 and 2022 and are deposited in the research collection of Thomas Wood (Naturalis Biodiversity Center, The Netherlands), in the FLOWer Lab collection at the University of Coimbra (Portugal), in the Andreia Penado collection at the Natural History and Science Museum of the University of Porto (MHNC-UP) (Portugal) and in the InBIO Barcoding Initiative (IBI) reference collection (Vairão, Portugal). New information: Of the 514 species sequenced, 75 species from five different families are new additions to the Barcode of Life Data System (BOLD) and 112 new BINs were added. Whilst the majority of species were assigned to a single BIN (94.9%), 27 nominal species were assigned to multiple BINs. Although the placement into multiple BINs may simply reflect genetic diversity and variation, it likely also represents currently unrecognised species-level diversity across diverse taxa, such as Amegillaalbigena Lepeletier, 1841, Andrenarussula Lepeletier, 1841, Lasioglossumleucozonium (Schrank, 1781), Nomadafemoralis Morawitz, 1869 and Sphecodesalternatus Smith, 1853. Further species pairs of Colletes, Hylaeus and Nomada were placed into the same BINs, emphasising the need for integrative taxonomy within Iberia and across the Mediterranean Basin more broadly. These data substantially contribute to our understanding of bee genetic diversity and DNA barcodes in Iberia and provide an important baseline for ongoing taxonomic revisions in the West Palaearctic biogeographical region.

Projected decline in European bumblebee populations in the twenty-first century.

Habitat degradation and climate change are globally acting as pivotal drivers of wildlife collapse, with mounting evidence that this erosion of biodiversity will accelerate in the following decades1-3. Here, we quantify the past, present and future ecological suitability of Europe for bumblebees, a threatened group of pollinators ranked among the highest contributors to crop production value in the northern hemisphere4-8. We demonstrate coherent declines of bumblebee populations since 1900 over most of Europe and identify future large-scale range contractions and species extirpations under all future climate and land use change scenarios. Around 38-76% of studied European bumblebee species currently classified as 'Least Concern' are projected to undergo losses of at least 30% of ecologically suitable territory by 2061-2080 compared to 2000-2014. All scenarios highlight that parts of Scandinavia will become potential refugia for European bumblebees; it is however uncertain whether these areas will remain clear of additional anthropogenic stressors not accounted for in present models. Our results underline the critical role of global change mitigation policies as effective levers to protect bumblebees from manmade transformation of the biosphere.

Diverse pollen nutrition can improve the development of solitary bees but does not mitigate negative pesticide impacts.

Floral resource loss and pesticide exposure are major threats to bees in intensively managed agroecosystems, but interactions among these drivers remain poorly understood. Altered composition and lowered diversity of pollen nutrition may reinforce negative pesticide impacts on bees. Here we investigated the development and survival of the solitary bee Osmia bicornis provisioned with three different pollen types, as well as a mixture of these types representing a higher pollen diversity. We exposed bees of each nutritional treatment to five pesticides at different concentrations in the laboratory. Two field-realistic concentrations of three nicotinic acetylcholine receptor (nAChR) modulating insecticides (thiacloprid, sulfoxaflor and flupyradifurone), as well as of two fungicides (azoxystrobin and tebuconazole) were examined. We further measured the expression of two detoxification genes (CYP9BU1, CYP9BU2) under exposure to thiacloprid across different nutrition treatments as a potential mechanistic pathway driving pesticide-nutrition interactions. We found that more diverse pollen nutrition reduced development time, enhanced pollen efficacy (cocoon weight divided by consumed pollen weight) and pollen consumption, and increased weight of O. bicornis after larval development (cocoon weight). Contrary to fungicides, high field-realistic concentrations of all three insecticides negatively affected O. bicornis by extending development times. Moreover, sulfoxaflor and flupyradifurone also reduced pollen efficacy and cocoon weight, and sulfoxaflor reduced pollen consumption and increased mortality. The expression of detoxification genes differed across pollen nutrition types, but was not enhanced after exposure to thiacloprid. Our findings highlight that lowered diversity of pollen nutrition and high field-realistic exposure to nAChR modulating insecticides negatively affected the development of O. bicornis, but we found no mitigation of negative pesticide impacts through increased pollen diversity. These results have important implications for risk assessment for bee pollinators, indicating that negative effects of nAChR modulating insecticides to developing solitary bees are currently underestimated.

A case study of the diet-microbiota-parasite interplay in bumble bees.

AIMS: Diets and parasites influence the gut bacterial symbionts of bumble bees, but potential interactive effects remain overlooked. The main objective of this study was to assess the isolated and interactive effects of sunflower pollen, its phenolamides, and the widespread trypanosomatid Crithidia sp. on the gut bacterial symbionts of Bombus terrestris males. METHODS AND RESULTS: Bumble bee males emerged in microcolonies fed on either (i) willow pollen (control), (ii) sunflower pollen, or (iii) willow pollen spiked with phenolamide extracts from sunflower pollen. These microcolonies were infected by Crithidia sp. or were pathogen-free. Using 16S rRNA amplicon sequencing (V3-V4 region), we observed a significant alteration of the beta diversity but not of the alpha diversity in the gut microbial communities of males fed on sunflower pollen compared to males fed on control pollen. Similarly, infection by the gut parasite Crithidia sp. altered the beta diversity but not the alpha diversity in the gut microbial communities of males, irrespective of the diet. By contrast, we did not observe any significant alteration of the beta or alpha diversity in the gut microbial communities of males fed on phenolamide-enriched pollen compared to males fed on control pollen. Changes in the beta diversity indicate significant dissimilarities of the bacterial taxa between the treatment groups, while the lack of difference in alpha diversity demonstrates no significant changes within each treatment group. CONCLUSIONS: Bumble bees harbour consistent gut microbiota worldwide, but our results suggest that the gut bacterial communities of bumble bees are somewhat shaped by their diets and gut parasites as well as by the interaction of these two factors. This study confirms that bumble bees are suitable biological surrogates to assess the effect of diet and parasite infections on gut microbial communities.

The wild solitary bees Andrena vaga, Anthophora plumipes, Colletes cunicularius, and Osmia cornuta microbiota are host specific and dominated by endosymbionts and environmental microorganisms.

We characterized the microbial communities of the crop, midgut, hindgut, and ovaries of the wild solitary bees Andrena vaga, Anthophora plumipes, Colletes cunicularius, and Osmia cornuta through 16S rRNA gene and ITS2 amplicon sequencing and a large-scale isolation campaign. The bacterial communities of these bees were dominated by endosymbionts of the genera Wolbachia and Spiroplasma. Bacterial and yeast genera representing the remaining predominant taxa were linked to an environmental origin. While only a single sampling site was examined for Andrena vaga, Anthophora plumipes, and Colletes cunicularius, and two sampling sites for Osmia cornuta, the microbiota appeared to be host specific: bacterial, but not fungal, communities generally differed between the analyzed bee species, gut compartments and ovaries. This may suggest a selective process determined by floral and host traits. Many of the gut symbionts identified in the present study are characterized by metabolic versatility. Whether they exert similar functionalities within the bee gut and thus functional redundancy remains to be elucidated.

Trace metals with heavy consequences on bees: A comprehensive review.

The pervasiveness of human imprint on Earth is alarming and most animal species, including bees (Hymenoptera: Apoidea: Anthophila), must cope with several stressors. Recently, exposure to trace metals and metalloids (TMM) has drawn attention and has been suggested as a threat for bee populations. In this review, we aimed at bringing together all the studies (n = 59), both in laboratories and in natura, that assessed the effects of TMM on bees. After a brief comment on semantics, we listed the potential routes of exposure to soluble and insoluble (i.e. nanoparticle) TMM, and the threat posed by metallophyte plants. Then, we reviewed the studies that addressed whether bees could detect and avoid TMM in their environment, as well as the ways bee detoxify these xenobiotics. Afterwards, we listed the impacts TMM have on bees at the community, individual, physiological, histological and microbial levels. We discussed around the interspecific variations among bees, as well as around the simultaneous exposure to TMM. Finally, we highlighted that bees are likely exposed to TMM in combination or with other stressors, such as pesticides and parasites. Overall, we showed that most studies focussed on the domesticated western honey bee and mainly addressed lethal effects. Because TMM are widespread in the environment and have been shown to result in detrimental consequences, evaluating their lethal and sublethal effects on bees, including non-Apis species, warrants further investigations.

Fertilizer and herbicide alter nectar and pollen quality with consequences for pollinator floral choices.

Background: Pollinating insects provide economically and ecologically valuable services, but are threatened by a variety of anthropogenic changes. The availability and quality of floral resources may be affected by anthropogenic land use. For example, flower-visiting insects in agroecosystems rely on weeds on field edges for foraging resources, but these weeds are often exposed to agrochemicals that may compromise the quality of their floral resources. Methods: We conducted complementary field and greenhouse experiments to evaluate the: (1) effect of low concentrations of agrochemical exposure on nectar and pollen quality and (2) relationship between floral resource quality and insect visitation. We applied the same agrochemcial treatments (low concentrations of fertilizer, low concentrations of herbicide, a combination of both, and a control of just water) to seven plant species in the field and greenhouse. We collected data on floral visitation by insects in the field experiment for two field seasons and collected pollen and nectar from focal plants in the greenhouse to avoid interfering with insect visitation in the field. Results: We found pollen amino acid concentrations were lower in plants exposed to low concentrations of herbicide, and pollen fatty acid concentrations were lower in plants exposed to low concentrations of fertilizer, while nectar amino acids were higher in plants exposed to low concentrations of either fertilizer or herbicide. Exposure to low fertilizer concentrations also increased the quantity of pollen and nectar produced per flower. The responses of plants exposed to the experimental treatments in the greenhouse helped explain insect visitation in the field study. The insect visitation rate correlated with nectar amino acids, pollen amino acids, and pollen fatty acids. An interaction between pollen protein and floral display suggested pollen amino acid concentrations drove insect preference among plant species when floral display sizes were large. We show that floral resource quality is sensitive to agrochemical exposure and that flower-visiting insects are sensitive to variation in floral resource quality.

Evaluation of Tandem Mass Spectrometry Experiments in the Negative Ionization Mode for Phenolamide Regioisomer Characterization.

Phenolamides are abundant specialized metabolites found in nature and consist of hydroxycinnamic acids mono- or polyconjugated with polyamines. Their participation in flower development is well-documented, and their presence in pollen raises the question of their role in pollen/pollinator interactions. The structural characterization of phenolamides is complicated by the presence of positional isomers and stereoisomers. Liquid chromatography coupled to tandem mass spectrometry in the positive ionization mode is becoming very popular in phenolamide structural characterization. However, collision-induced transamidation processes that cause the swapping of side chains have been detected, making it difficult to distinguish regioisomers with this technique. In the present report, we explore the dissociation processes undergone by the [M - H]- ions of spermidine-based phenolamides as model compounds. We describe two original competitive dissociation routes, namely, the phenolate and imidate pathways, to account for the observed fragmentation reactions undergone by collisional activated standard phenolamide anions. Whereas the phenolate pathway is regioselective at the central position for spermidine, the imidate pathway, requiring a deprotonated amide, only occurs at the extremities. Tandem mass spectrometry experiments on negatively charged phenolamide ions may then outperform their positive ionization mode counterparts for the distinction between phenolamide regioisomers and globally for the identification of phenolamides in natural extracts.

Convivina is a specialised core gut symbiont of the invasive hornet Vespa velutina.

We provide a culturomics analysis of the cultivable bacterial communities of the crop, midgut and hindgut compartments, as well as the ovaries, of the invasive insect Vespa velutina, along with a cultivation-independent analysis of samples of the same nest through 16S rRNA amplicon sequencing. The Vespa velutina bacterial symbiont community was dominated by the genera Convivina, Fructobacillus, Lactiplantibacillus, Lactococcus, Sphingomonas and Spiroplasma. Lactococcus lactis and Lactiplantibacillus plantarum represented generalist core lactic acid bacteria (LAB) symbionts, while Convivina species and Fructobacillus fructosus represented highly specialised core LAB symbionts with strongly reduced genome sizes. Sphingomonas and Spiroplasma were the only non-LAB core symbionts but were not isolated. Convivina bacteria were particularly enriched in the hornet crop and included Convivina intestini, a species adapted towards amino acid metabolism, and Convivina praedatoris sp. nov. which was adapted towards carbohydrate metabolism.

Challenges related to the application of analytical methods to control insect meals in the context of European legislation.

Since their approval for use in aquaculture in 2017, processed insect proteins have been extensively studied for their nutritional quality in animal feed. This new type of meal is highly promising but requires, as for other products used in animal feed, strict sanitary control in accordance with European legislation. Within this legal framework, light microscopy and PCR remain the official methods but have some analytical limitations that other methods could overcome. This paper aims to provide an overview of the European legislation concerning use of processed insect proteins, but also to highlight the advantages and disadvantages of the official methods for their analysis. It also points out other analytical methods, which have already proved their worth for the analysis of processed animal proteins, which could be used as complementary methods.

Microbiota and pathogens in an invasive bee: Megachile sculpturalis from native and invaded regions.

The present study aimed to characterise the bacterial, fungal and parasite gut community of the invasive bee Megachile sculpturalis sampled from native (Japan) and invaded (USA and France) regions via 16S rRNA and ITS2 amplicon sequencing and PCR detection of bee microparasites. The bacterial and fungal gut microbiota communities in bees from invaded regions were highly similar and differed strongly from those obtained in Japan. Core amplicon sequence variants (ASVs) within each population represented environmental micro-organisms commonly present in bee-associated niches that likely provide beneficial functions to their host. Although the overall bacterial and fungal communities of the invasive M. sculpturalis in France and the co-foraging native bees Anthidium florentinum and Halictus scabiosae, were significantly different, five out of eight core ASVs were shared suggesting common environmental sources and potential transmission. None of the 46 M. sculpturalis bees analysed harboured known bee pathogens, while microparasite infections were common in A. florentinum, and rare in H. scabiosae. A common shift in the gut microbiota of M. sculpturalis in invaded regions as a response to changed environmental conditions, or a founder effect coupled to population re-establishment in the invaded regions may explain the observed microbial community profiles and the absence of parasites. While the role of pathogen pressure in shaping biological invasions is still debated, the absence of natural enemies may contribute to the invasion success of M. sculpturalis.

Pollen as Bee Medicine: Is Prevention Better than Cure?

To face environmental stressors such as infection, animals may display behavioural plasticity to improve their physiological status through ingestion of specific food. In bees, the significance of medicating pollen may be limited by their ability to exploit it. Until now, studies have focused on the medicinal effects of pollen and nectar after forced-feeding experiments, overlooking spontaneous intake. Here, we explored the medicinal effects of different pollen on Bombus terrestris workers infected by the gut parasite Crithidia bombi. First, we used a forced-feeding experimental design allowing for the distinction between prophylactic and therapeutic effects of pollen, considering host tolerance and resistance. Then, we assessed whether bumble bees favoured medicating resources when infected to demonstrate potential self-medicative behaviour. We found that infected bumble bees had a lower fitness but higher resistance when forced to consume sunflower or heather pollen, and that infection dynamics was more gradual in therapeutic treatments. When given the choice between resources, infected workers did not target medicating pollen, nor did they consume more medicating pollen than uninfected ones. These results emphasize that the access to medicating resources could impede parasite dynamics, but that the cost-benefit trade-off could be detrimental when fitness is highly reduced.

A phylogenomic and comparative genomic analysis of Commensalibacter, a versatile insect symbiont.

BACKGROUND: To understand mechanisms of adaptation and plasticity of pollinators and other insects a better understanding of diversity and function of their key symbionts is required. Commensalibacter is a genus of acetic acid bacterial symbionts in the gut of honey bees and other insect species, yet little information is available on the diversity and function of Commensalibacter bacteria. In the present study, whole-genome sequences of 12 Commensalibacter isolates from bumble bees, butterflies, Asian hornets and rowan berries were determined, and publicly available genome assemblies of 14 Commensalibacter strains were used in a phylogenomic and comparative genomic analysis. RESULTS: The phylogenomic analysis revealed that the 26 Commensalibacter isolates represented four species, i.e. Commensalibacter intestini and three novel species for which we propose the names Commensalibacter melissae sp. nov., Commensalibacter communis sp. nov. and Commensalibacter papalotli sp. nov. Comparative genomic analysis revealed that the four Commensalibacter species had similar genetic pathways for central metabolism characterized by a complete tricarboxylic acid cycle and pentose phosphate pathway, but their genomes differed in size, G + C content, amino acid metabolism and carbohydrate-utilizing enzymes. The reduced genome size, the large number of species-specific gene clusters, and the small number of gene clusters shared between C. melissae and other Commensalibacter species suggested a unique evolutionary process in C. melissae, the Western honey bee symbiont. CONCLUSION: The genus Commensalibacter is a widely distributed insect symbiont that consists of multiple species, each contributing in a species specific manner to the physiology of the holobiont host.

The InBIO Barcoding Initiative Database: contribution to the knowledge on DNA barcodes of cuckoo wasps, with the description of new species from the Iberian Peninsula (Hymenoptera, Chrysididae).

Background: DNA barcoding technologies have provided a powerful tool for the fields of ecology and systematics. Here, we present a part of the InBIO Barcoding Initiative Database: contribution to the knowledge on DNA barcodes of cuckoo wasps (Hymenoptera, Chrysididae) dataset representing 144 specimens and 103 species, covering approximately 44% of the Iberian and 21% of the European fauna. The InBIO Barcoding Initiative (IBI - DNA Barcoding Portuguese terrestrial invertebrate biodiversity) aims to fill the barcoding gap for the terrestrial invertebrate taxa. All DNA extractions are deposited in the IBI collection at CIBIO, Research Center in Biodiversity and Genetic Resources and specimens are deposited in the University of Mons collection (Belgium) and in the Natur-Museum in Lucerne (Switzerland). New information: This dataset increases the knowledge on the DNA barcodes and distribution of 102 species of cuckoo wasps. A total of 52 species, from 11 different genera, were new additions to the Barcode of Life Data System (BOLD), with DNA barcodes for another 44 species added from under-represented taxa in BOLD. All specimens have their DNA barcodes publicly accessible through the BOLD online database. Nine cuckoo wasp species are newly recorded for Portugal. Additionally, two new species for science are described: Chrysiscrossi Rosa, sp. nov. from southern Portugal and Hedychridiumcalcarium Rosa, sp. nov. from eastern Spain. Several taxonomic changes are proposed and Hedychrumrutilans Dahlbom, 1845 is found to consist of two different taxa that can be found in sympatry, Hedychrumrutilans s. str. and Hedychrumviridaureum Tournier, 1877 stat. nov. Stilbumwestermanni Dahlbom, 1845 stat. nov. is confirmed as distinct from Stilbumcalens (Fabricius, 1781), with the latter species not confirmed as present in Iberia; barcoded Stilbum material from Australia is distinct and represents Stilbumamethystium (Fabricius, 1775) sp. resurr.; Portuguese material identified as Hedychridiumchloropygum Buysson, 1888 actually belongs to Hedychridiumcaputaureum Trautmann & Trautmann, 1919, the first confirmed record of this species from Iberia. Philoctetesparvulus (Dahlbom, 1845) is confirmed to be a synonym of Philoctetespunctulatus (Dahlbom, 1845). Chrysislusitanica Bischoff, 1910 is confirmed as a valid species. Chrysishebraeica Linsenmaier, 1959 stat. nov. is raised to species status.

The new annotated checklist of the wild bees of Europe (Hymenoptera: Anthophila).

At a time when nature conservation has become essential to ensure the long-term sustainability of our environment, it is widely acknowledged that conservation actions must be implemented within a solid taxonomic framework. In preparation for the upcoming update of the IUCN Red List, we here update the European checklist of the wild bees (sensu the IUCN geographical framework). The original checklist, published in 2014, was revised for the first time in 2017. In the present revision, we add one genus, four subgenera and 67 species recently described, 40 species newly recorded since the latest revision (including two species that are not native to Europe), 26 species overlooked in the previous European checklists and 63 published synonymies. We provide original records for eight species previously unknown to the continent and, as original taxonomic acts, we provide three new synonyms, we consider two names as nomina nuda, ten names as nomina dubia, three as species inquirenda, synonymize three species and exclude 40 species from the previous checklist. Around a hundred other taxonomic changes and clarifications are also included and discussed. The present work revises the total number of genera for IUCN Europe to 77 and the total number of species to 2,138. In addition to specifying the taxonomic changes necessary to update the forthcoming Red List of European bees, we discuss the sampling and taxonomic biases that characterise research on the European bee fauna and highlight the growing importance of range expansions and species invasions.

Nutritional stress exacerbates impact of a novel insecticide on solitary bees' behaviour, reproduction and survival.

Pesticide exposure and food stress are major threats to bees, but their potential synergistic impacts under field-realistic conditions remain poorly understood and are not considered in current pesticide risk assessments. We conducted a semi-field experiment to examine the single and interactive effects of the novel insecticide flupyradifurone (FPF) and nutritional stress on fitness proxies in the solitary bee Osmia bicornis. Individually marked bees were released into flight cages with monocultures of buckwheat, wild mustard or purple tansy, which were assigned to an insecticide treatment (FPF or control) in a crossed design. Nutritional stress, which was high in bees foraging on buckwheat, intermediate on wild mustard and low on purple tansy, modulated the impact of insecticide exposure. Within the first day after application of FPF, mortality of bees feeding on buckwheat was 29 times higher compared with control treatments, while mortality of FPF exposed and control bees was similar in the other two plant species. Moreover, we found negative synergistic impacts of FPF and nutritional stress on offspring production, flight activity, flight duration and flower visitation frequency. These results reveal that environmental policies and risk assessment schemes that ignore interactions among anthropogenic stressors will fail to adequately protect bees and the pollination services they provide.

A large-scale dataset reveals taxonomic and functional specificities of wild bee communities in urban habitats of Western Europe.

Wild bees are declining, mainly due to the expansion of urban habitats that have led to land-use changes. Effects of urbanization on wild bee communities are still unclear, as shown by contrasting reports on their species and functional diversities in urban habitats. To address this current controversy, we built a large dataset, merging 16 surveys carried out in 3 countries of Western Europe during the past decades, and tested whether urbanization influences local wild bee taxonomic and functional community composition. These surveys encompassed a range of urbanization levels, that were quantified using two complementary metrics: the proportion of impervious surfaces and the human population density. Urban expansion, when measured as a proportion of impervious surfaces, but not as human population density, was significantly and negatively correlated with wild bee community species richness. Taxonomic dissimilarity of the bee community was independent of both urbanization metrics. However, occurrence rates of functional traits revealed significant differences between lightly and highly urbanized communities, for both urbanization metrics. With higher human population density, probabilities of occurrence of above-ground nesters, generalist and small species increased. With higher soil sealing, probabilities of occurrence of above-ground nesters, generalists and social bees increased as well. Overall, these results, based on a large European dataset, suggest that urbanization can have negative impacts on wild bee diversity. They further identify some traits favored in urban environments, showing that several wild bee species can thrive in cities.