Wild Bees Research Articles

Legacy industrial pollutants in the South American black bumblebee Bombus pauloensis inhabiting peri-urban and rural fields from theArgentineanpampas.

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are persistent organic pollutants (POPs), banned worldwide due to their effects on biota. In South America, studies on POPs in wild bees, like Bombus pauloensis, a continentally widespread bumblebee, are lacking, and information on its health is limited. This study assessed, by GC-ECD, PCBs and PBDEs levels in B. pauloensis, flowers and soils from fields located at different distances from urban activities: PU and LF, two peri-urban fields near the local industrial park, with LF also next to an overloaded solid waste landfill, and RU, a rural field. For all matrices, the peri-urban fields registered significant higher pollutant levels compared to RU, especially in workers, where LF showed the highest ∑PCBs and ∑PBDEs levels (21.09 ± 2.57 and 10.29 ± 0.37ng/g, respectively). In males, PU and LF showed the highest nominal ∑PCBs (PU; 24.97 ± 1.03ng/g) and ∑PBDE (LF; 10.39 ± 0.77ng/g) concentrations, which confirms the influence of the landfill. Across matrices, lighter PCB congeners dominated, possibly explained by the past use of PCB mixtures and atmospheric transport, and a biomagnification pattern was observed. PCB concentrations were similar to those proven to cause sublethal effects in bees, and males showed significantly higher POP levels than workers. Thus, drivers and population effects were discussed. This may be one of the first studies of industrial POPs in wild bees in South America, emphasizing the need to look beyond insecticides and unique castes in environmental exposure studies.

Evaluation of herbicide formulations and spreading agents on survival of the bumblebee Bombus impatiens following spray and contact exposure.

Surfactants are often included as co-formulants in the application of herbicides to aid in spreading and adherence to plant surfaces, but toxicity to native bees has not been extensively tested. In a set of progressive experiments, we evaluated effects of products containing glyphosate and spreading agents, as well as spreading agents alone, on bumblebees (Bombus impatiens Cresson) using parametric survival analysis. We test spreaders from multiple chemical classes including Silwet L-77© (trisiloxane), Alligare 90© (polyoxyethylene), and Southern Ag SA-50© (C10-16 alcohols). We report low lethality of high-glyphosate herbicide formulations (Rodeo©), but bee mortality increased ~20% with addition of a silicone-based spreading agent (Silwet L-77©). Spreaders alone strongly affected bee survival: effects were concentration-specific and did not differ depending on exposure method (spray application vs. application to surfaces contacted by bees). The widely used trisiloxane-based spreader Silwet L-77© was especially hazardous, and exposure to high concentrations of Silwet L-77© caused rapid and near-total mortality in B. impatiens. Analysis of whole-bee cuticle extracts after exposure revealed clear differences in the cuticular hydrocarbon profiles associated with exposure to spreading agents: the alkane n-hexacosane was present in all extracts but was detected in greater relative abundance from bees exposed to Silwet L-77© and Alligare 90©. To support wild bee conservation efforts, we recommend substituting alcohol-based spreaders for siloxane-based spreaders when possible. In addition, certain cuticular hydrocarbons may be useful as biomarkers of previous exposure to certain surfactants, which can aid investigations evaluating causes of bumblebee decline across landscapes.

Plants for Wild Bees—Field Records in Bulgaria

One of the eight shortfalls in European wild bee data is the knowledge of the flowering plants they favor. This knowledge is of particular importance for bee gardens and wildflower strips initiatives aiming to provide forage for the wild bees. The aim of this study is to provide a list of plants that are used for food by certain taxa of wild bees in Bulgaria and to evaluate their potential for cultivation in bee gardens and wildflower strips. In relation to this, we discuss the food plant specialization of the wild bees. We summarize our observations on the pollination of certain plants and faunistic records considering the food plants in several grassland habitats on the territory of Bulgaria at altitudes between 0 and 1500 m above sea level, during the last 30 years. More than 54 taxa of wild bees are listed. They belong to the families Apidae, Andrenidae, Colletidae, Halictidae, and Megachilidae. Some of these bees are identified to the species level, and others to the genus or family level. Among the recorded wild bees are observed eight oligolectic species (22.2%). The listed bees are flower visitors of 60 plant taxa belonging to 20 families, which offer nectar and/or pollen. The wild bees’ food plants are predominantly from the families Fabaceae (15 species), Lamiaceae (14 species), Asteraceae (9 species), etc. The perennials are 67%, while annuals are 9%, annual or biennial 6%, biennials 5%, etc. We discuss the seed germination specifics of these plants. More studies are needed in this field. The conservation of wild bees may be supported by wildflower restoration activities, but the process depends on many factors, including seed germination difficulties. Therefore, the natural grassland habitats must be preserved and protected.

A Comparison of Pollination Efficiency Between Wild Bumble Bees and Introduced Honey Bees on Polygonatum cyrtonema

To clarify the pollination contributions of introduced honey bees and native wild bees, we compared their pollination efficiency on a perennial herb, Polygonatum cyrtonema Hua. The flower’s traits and bees’ body traits were measured to quantify the mechanical fit between the bee species and flower. Pollen removal and deposition per visit, visit frequency, and visit duration per flower were investigated. The results show that both native bumble bees (worker bees of Bombus trifasciatus Smith) and introduced honey bees (Apis mellifera L.) are effective pollinators, but bumble bees play a more important role in pollination, due to their higher visit frequency and slightly higher pollen transfer efficiency. The bumble bees removed and deposited significantly more pollen grains per visit than the honey bees (both p < 0.001). The faster visiting speed and shorter visit duration of the bumble bees, combined with their larger body size and longer proboscises, may have contributed to their higher pollen transfer efficiency. The pollination success of P. cyrtonema depends on its pollinators. This study is the first to report on the pollination efficiency of floral visitors on P. cyrtonema. Our findings highlight the importance of conserving native bumble bee populations to ensure the reproductive success of P. cyrtonema. Future studies should focus on their management to minimize potential disruptions to native pollination contribution.

Standardized protocol for collecting bee samples for parasite and pathogen data

Internal parasites and pathogens have not been a focus of wild bee systematic data collection efforts to-date but are important to document because they have been strongly linked to bee declines. Here, we provide a standardized protocol for collecting fresh bee tissue samples for generating parasite and pathogen data. The protocol emphasizes appropriate handling and storage conditions and data standards. It can be embedded within bee health monitoring projects or used by individual data collection efforts that aim to generate parasite and pathogen data now and in the future. This protocol is part of a series developed in association with the U.S. National Native Bee Monitoring Network to standardize bee monitoring practices.

Estimating occupancy of focal bee species

Current bee monitoring efforts have a limited capacity for understanding factors affecting wild bee population changes, including the effects of management. To improve the effectiveness of wild bee monitoring, we first discuss principles of biological monitoring and provide a framework to design monitoring projects to estimate species occupancy, where occupancy is defined as the probability that a Sampling Unit or site is occupied by the focal species. Monitoring practitioners should first define the desired goal or question of monitoring and secondly select the appropriate state variable for monitoring (e.g., species richness, occupancy, abundance). These represent two critical, yet often overlooked, steps in the development of wild bee monitoring projects. As with all forms of demographic monitoring, practitioners who are interested in estimating species occupancy will need to develop a sampling scheme tailored to meet their monitoring objectives. Defining key sampling terms will provide the architecture of their scheme, including the Area of Interest, Sampling Unit, Season, and Replicate Survey. We also highlight data standards, including core data fields that must be collected during Surveys for bee occupancy data and additional, recommended data fields. We illustrate how these monitoring concepts are being applied to the design of a real-world monitoring project for the federally endangered rusty patched bumble bee (Bombus affinis Cresson). This framework was developed in association with the U.S. National Native Bee Monitoring Network.

Management factors strongly affect flower-visiting insects in intensive apple orchards

Management factors strongly affect flower-visiting insects in intensive apple orchards

Answering key bumble bee conservation questions by studying discovered wild nests: A Bombus affinis case study

Abstract The nesting ecology of wild bumble bees is not well resolved, but information learned from discovered nests can be of great conservation value. Data collected at nests on foraging patterns, caste‐specific behaviour and health (e.g., pathogens) are invaluable for understanding bumble bee behaviour and ecology, but difficult to decipher solely from foraging observations away from the nest. Post‐senescence nest excavation allows the estimation of colony size, caste numbers, documents pest incidence and provides opportunities to examine nest material for stressors (e.g., pesticides) and to use nest material for training purposes (e.g., conservation dogs). Wild nests are often found opportunistically, and there is an absence of standardised guidance on data collection. We provide an action plan to ensure the data collection is comparable across studies. This framework includes key conservation questions and methodological guidelines for both for in situ and post‐season nest data collection and is ordered by increasing complexity of data collection methods. To illustrate our framework, we provide an example with recently discovered Bombus affinis (rusty patched bumble bee) nests. Through observations at B. affinis nests, we discovered novel patterns of activity, changing activity levels over time, the timing of male and gyne production, variable timing in nest senescence, and associations of nests with past rodent activity. Although individual nest discoveries may be of limited value in forwarding conservation strategies, the aggregate collections of many similar datasets can be of critical importance for species of conservation concern.

New distribution records of wild bees (Hymenoptera, Apoidea) in South Tyrol (Italy): expanding the wild bee database.

Throughout South Tyrol, in northern Italy, there is a data deficiency relating to wild bee species pool. Here, we present significant findings from the collection of 3,313 wild bees gathered over two separate studies conducted in consecutive years. Our research focused on the impact of landscape heterogeneity, temperature and land-use change on wild bee communities and their pollination services in an agricultural and mountainous landscape. This article provides a detailed account of the 150 identified wild bee species collected using coloured pan traps. We report habitat type, occurrence data, threat status, sociality, nesting strategy and diet breadth. In Italian regions where information on wild bee distribution is lacking or outdated, sharing data is crucial for developing conservation policies. The compiled species list strengthens regional and national wild bee database by providing new distribution data for extinction-threatened species, such as Dufoureadentiventris (Nylander, 1848), Dufoureainermis (Nylander, 1848), Lasioglossumbrevicorne (Schenck, 1870), Lasioglossumlaevigatum (Kirby, 1802), Lasioglossummonstrificum (Morawitz, 1891), Nomadamutica Morawitz, 1872 and Nomadavillosa Thomson, 1870. Additionally, we present recent findings of species that are valuable for understanding range expansions, recording species previously unreported in South Tyrol and updating historical data for the region.

Investigation and Study on the Biology and Morphology of Apis florea and Apis dorsata in Southern China

Honey bees are crucial pollinators that play a vital role in maintaining ecological balance. The colonies of managed honey bees in China increased rapidly in the past 20 years. Whether the rapid increase in managed bee populations would affect the survival of wild honey bees deserves attention. There are four species of the genus Apis in Guangxi, China, including Apis florea, Apis dorsata, Apis mellifera ligustica, and Apis cerana. This study conducted an investigation on the biological characteristics of the four species and measured 40 morphological characteristics. The results showed that for the four species, their swarming periods, mating periods, the emergence of drones, and the nectar and pollen source plants highly overlap. This leads to potential competition for the optimum mating space, nectar, and pollen. The comparison of morphological traits between samples collected in 2012 and 2023 showed that the aspect ratios of the forewings of both Apis florea and Apis dorsata have significantly increased. This change may be attributed to the rapid increase in managed honey bees’ populations, which has encroached upon the living spaces of A. florea and A. dorsata. The results of coefficient of variations showed that Apis florea and Apis dorsata exhibit high genetic diversity. Our results indicated that the increased colonies’ number of managed honey bees has an effect on Apis florea and Apis dorsata, but they are not facing great threats to their survival. Continuous monitoring of the the diversity of Apis florea and Apis dorsata must be maintained. Preserving wild honey bees is of great significance for the ecological balance.

Poor air quality raises mortality in honey bees, a concern for all pollinators

Human well-being relies on the presence and role of pollinators, as they contribute to the vitality of ecosystems, support the reproduction of wild plants, increase crop yields, and strengthen overall food security. While wild bee populations are dwindling due to climate and environmental change, there has been a notable 45% rise globally in the number of managed honey bee (Apis mellifera) colonies over the past five decades. Given their economic significance and their relative ease of tracking, honey bees have the potential to serve as bioindicators of global pollinator health. Consequently, honey bees have emerged as a keystone species requiring protection and conservation efforts. Here, we investigate the intricate relationship between air quality, environmental factors, and honey bee mortality across Canada and the United States. Using statistical and machine learning modeling, our findings underscore the honey bee’s role as a bioindicator. We found that air quality is an important predictor of honey bee mortality. The risk of honey bee mortality increased with poor air quality (ozone and Air Quality Health Index) but was substantially reduced in regions with greater vegetation availability (Normalized Difference Vegetation Index). Therefore, our study offers a beacon of hope: improving management practices by increasing greenery can significantly mitigate the impact of deteriorating air quality on honey bees, providing a vital solution to safeguard our essential pollinators.

Honeybees interfere with wild bees in apple pollination in China

Abstract Honeybees (Apis mellifera) are increasingly used in commercial crop production, while wild bees are also important pollinators. Few studies have investigated the relative importance of honeybees and wild bees for apple pollination and whether the contribution of wild bees is affected by increasing numbers of honeybees. Here, we conducted experiments in 52 commercially important Fuji apple orchards across three apple production areas in China, to investigate how wild bees, honeybees and their interaction influences apple quantity (fruit set, weight) and quality (seed number). Both honeybees and wild bees contributed to apples production, resulting in an overall 996%, 26% and 64% increase of apple fruit set, fruit weight and seed number, respectively. We found a hump‐shaped relationship between bee density and fruit set and fruit weight with the maximum fruit set at intermediate bee density, but honeybees reached the maximum only with one and a half times higher numbers than wild bees. Furthermore, when honeybee activity density was low, an increase in wild bee activity density and species richness led to enhanced pollination contribution. Conversely, when honeybee activity density was high, increased wild bee activity density and species richness were associated with reduced pollination contribution. Additionally, the highest fruit set was observed at high densities of wild bees and intermediate densities of honeybees. These results indicate that high honeybee activity density may interfere with the pollination services provided by wild bees in apple orchards. Synthesis and applications. Both honeybees and wild bees contribute to apple pollination and production, but wild bees evidenced much higher pollination efficiency than honeybees. Importantly, introducing high density of honeybee colonies appeared to enhance competition with wild bees, decreasing their contribution to pollination. As highest fruit set was found with high wild bee densities, but only intermediate levels of honeybee densities, it is important to carefully assess the number of honeybee colonies before possible introduction of hives for apple production, in particular when wild bee diversity and density are high. Conserving wild bee diversity is of priority to harness pollination services in apple production, given their high diversity and pollination efficiency.

Influence of urban land cover and habitat quality on wild bees

Influence of urban land cover and habitat quality on wild bees

Data on the diet and nutrition of urban and rural bumblebees

Land-use changes, driven by agricultural intensification and urbanization, are major contributors to biodiversity loss, altering habitats and reducing available resources. These changes impact species’ foraging strategies, particularly in human-modified ecosystems. While dietary shifts due to land-use changes have been well-studied in vertebrates, similar research in invertebrates, such as wild bees, remains limited. The present data paper provides a comprehensive dataset on the pollen collected from urban and rural populations of two bumblebee species (Bombus lapidarius and B. pascuorum) in Switzerland, examining pollen composition, nutrient content, and diet breadth. Additionally, by analyzing pollen from both body and leg-baskets, the dataset also offers a comprehensive overview of plant-bumblebee interactions. The data help understand plant-bumblebee interactions, pollination services, nutritional supply to larvae, and the impact of land-use changes on these processes. Furthermore, the dataset can be integrated with existing plant trait data to explore the effects of non-native species and other ecological factors on bumblebee foraging and nutrition in anthropogenically modified landscapes.

Biodiversity-Friendly Management in Olive Groves Supports Pollinator Conservation in a Mediterranean Terraced Landscape.

While olive trees are primarily wind-pollinated, biodiversity-friendly management of the groves can contribute to the conservation of pollinating insects in olive agroecosystems. Previous research demonstrated that semi-natural habitats, such as herbaceous linear elements and woody areas, support the community of pollinators in agroecosystems. Less is known about the contribution of low-input olive groves with a permanent ground cover on terraced landscapes. This study investigated the relationship between pollinator communities and semi-natural habitats, including spontaneous vegetation, in a traditional terraced Mediterranean olive grove agroecosystem. The research employed pan traps to monitor wild bees and observation walks to assess the butterfly community across three different habitat types in spring, summer, and autumn during two growing seasons. Floral resources in the habitats were assessed during each sampling time. Analysis showed that herbaceous habitats support a higher abundance of wild bees than woody areas, while olive groves do not differ significantly from either habitat type, despite exhibiting the highest floral abundance. This suggests that habitat structure, rather than floral availability alone, plays a role in maintaining the wild bee community. For butterflies, results demonstrate that the overall abundance does not differ between habitats, while the species composition does. The study emphasizes the importance of preserving diverse habitats, and in particular low-input olive groves, within agricultural landscapes to support a wide range of pollinator species.

Integrating taxonomic, genetic and ecological data to explore the species richness of wild bees (Hymenoptera, Apoidea, Anthophila) of the Culuccia Peninsula (NE Sardinia, Italy)

Wild bees are essential pollinators of both native and cultivated plants, but their populations are declining worldwide. Conservation efforts are hindered by insufficient data, especially in the Mediterranean basin, which hosts some of the most diverse pollinator communities in the world. Particularly in Sardinia, the second largest island in the Mediterranean, information on the bee fauna is still limited. The aim of this work was to provide the first checklist of ApoideaAnthophila from an unexplored peninsula in north-eastern Sardinia (Italy), by combining traditional (morphologically-based) taxonomy and DNA barcoding. In addition, records of flower visits are provided and shown in a visitor network to enrich the scarce data on the associations between wild bees and plants in the Mediterranean Region. Bees were sampled from April to October 2022–2023 with two Malaise traps and nets. DNA was extracted to amplify sequences of the mitochondrial gene Cyotochrome oxydase I, which were then compared with those in BOLD using the identification tool and by constructing neighbor-joining phylogenetic trees. Seventy-six different species belonging to 29 genera and six families were collected and identified. A total of 212 COI sequences were obtained for 61 different species, many of which had not yet been sequenced from Italian populations. Five of the collected taxa are Sardo-Corsican endemics, whereas six species are newly recorded from Sardinia. Finally, we highlight potential taxonomic issues and new flower visit records, emphasizing the need for further research to better understand the taxonomy and ecology of this diverse group of insects toward their conservation.

Bumble bee gut microbial community structure differs between species and commercial suppliers, but metabolic potential remains largely consistent.

Bumble bees are key pollinators for natural and agricultural plant communities. Their health and performance are supported by a core gut microbiota composed of a few bacterial taxa. However, the taxonomic composition and community structure of bumble bee gut microbiotas can vary with bee species, environment, and origin (i.e., whether colonies come from the wild or a commercial rearing facility), and it is unclear whether metabolic capabilities therefore vary as well. Here we used metagenomic sequencing to examine gut microbiota community composition, structure, and metabolic potential across bumble bees from two different commercial Bombus impatiens suppliers, wild B. impatiens, and three other wild bumble bee species sampled from sites within the native range of all four species. We found that the community structure of gut microbiotas varied between bumble bee species, between populations from different origins within species, and between commercial suppliers. Notably, we found that Apibacter is consistently present in some wild bumble bee species-suggesting it may be a previously unrecognized core phylotype of bumble bees-and that commercial B. impatiens colonies can lack core phylotypes consistently found in wild populations. However, despite variation in community structure, the high-level metabolic potential of gut microbiotas was largely consistent across all hosts, including for metabolic capabilities related to host performance, though metabolic activity remains to be investigated.IMPORTANCEOur study is the first to compare genome-level taxonomic structure and metabolic potential of whole bumble bee gut microbiotas between commercial suppliers and between commercial and wild populations. In addition, we profiled the full gut microbiotas of three wild bumble bee species for the first time. Overall, our results provide new insight into bumble bee gut microbiota community structure and function and will help researchers evaluate how well studies conducted in one bumble bee population will translate to other populations and species. Research on taxonomic and metabolic variation in bumble bee gut microbiotas across species and origins is of increasing relevance as we continue to discover new ways that social bee gut microbiotas influence host health, and as some bumble bee species decline in range and abundance.

Wild Bee Assemblages and Pollination Networks of Managed Emergent Wetlands in Central New York, USA.

To effectively protect wild bee pollinators and the services they provide, it is critical to gather data on their distributions, life histories, and interactions with plants among a diversity of habitat types. Wetlands are underrepresented in bee surveys, despite having a great diversity of flowering plants and known importance to hundreds of species of wildlife. In this 2-year survey of a restored wetland complex in Central New York, over 9000 bees were collected, representing ≥ 109 species in 25 genera. We recorded 337 unique plant-pollinator associations, including those previously undocumented for the wetland obligate masked bee, Hylaeus nelumbonis (Robertson). Floral resources and bee genera were most diverse in August, and network analyses indicated September networks were the most connected, nested, and least modular. Floral resources also shifted towards being more native over the course of the season. Results show that emergent wetlands support diverse guilds of pollinators in the latter half of the growing season, and that wetland management can produce diverse conditions conducive to wild bee habitat.

A case for occupancy as a state variable for wild bee monitoring

A case for occupancy as a state variable for wild bee monitoring

The ground-nesting bee Anthophora plumipes as a model species for assessing effects of soil-mediated pesticide exposure

Though many wild bee species nest in the ground, little is known of their potential exposure to pesticide residues in soil, or the effects of such exposure. Here, we introduce Anthophora plumipes as a potential model ground-nesting solitary bee species for controlled exposure to pesticides through soil. Bees from a naturally occurring population were allowed to nest in loam blocks containing varying concentrations of the neonicotinoid imidacloprid. Measured residues of imidacloprid in brood provisions and in bee bodies remained at < 0.01% of the concentration in surrounding soil, suggesting limited migration of contaminants from soil to brood. Furthermore, imidacloprid contamination had no marked effect on the number, survival, body size or rate of parasitism of offspring at the tested concentrations (≤ 10 mg/kg). This species native to Eurasia and North Africa may be a suitable model for further research on the ecotoxicology of ground-nesting solitary bee species.