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opencc-by-4.0May 2020View details →

Agri-environment schemes enhance pollinator richness and abundance but bumblebee reproduction depends on field size

Insect-pollinated plant and pollinator data supporting the results reported in the article Geppert et al. (2020).

opencc-zeroDec 2019View details →

Mass-migrating bumblebees: an overlooked phenomenon with potential far-reaching implications for bumblebee conservation

1. Bumblebees are one of the most commonly studied pollinators, but they are declining in large parts of their distribution. Whether bumblebees can cope with anthropogenic disturbances such as climate change and habitat loss depends largely on their dispersal capacity. While bumblebee queen dispersal is estimated to be only a few kilometres, bird migration sites have documented mass-migration events with peak migration of 70 bumblebee queens per minute, indicating that bumblebees can migrate over larger distances than previously thought. 2. The open-access database trektellen.org contains ten daily counts of >1000 migrating queens past single points in the Netherlands, and one in the UK (total bumblebee records 65,430; range 1-11,142 individuals), mostly in early spring. Such mass-migration events are poorly documented in the scientific literature, and usually when describing migrations of other insects such as syrphids and social wasps. 3. Most common European bumblebee species were documented to migrate. Bumblebees were observed flying at sea, coming from sea, and flying towards the sea, showing that they can cross large water bodies. The wind direction might have helped to concentrate migration at landscape bottlenecks. On one day, bumblebee mass-migration was documented on two sites located 200 kilometres apart. Together with the concentrated and directional flight this suggests that they can migrate for several hundreds of kilometres. 4. Because most mass-migration events occur in spring, large scale shortage in suitable nesting sites may be the trigger for mass-migration (e.g. due to high queen survival or low vole numbers). Future studies should test whether this is the case, or whether bumblebees show annual seasonal migration. 5. Synthesis and applications. Much remains unclear about bumblebee migration, but it may have large consequences for the conservation of bumblebees and the ecosystem services they provide. For example, bumblebees in highly disturbed areas like agricultural landscapes may be continuously supplemented by queens from far-away productive natural areas. This suggests that large-scale conservation initiatives are required to maintain viable populations of common and endangered species. Structured observations and modern-day technology, like isotope analyses or radar monitoring, may shed light on the drivers and consequences of the overlooked phenomenon of bumblebee migration.

opencc-zeroDec 2018View details →

Data from: Phenology of farmland floral resources reveals seasonal gaps in nectar availability for bumblebees

Floral resources are known to be important in regulating wild pollinator populations and are therefore an important component of agri‐environment and restoration schemes which aim to support pollinators and their associated services. However, the phenology of floral resources is often overlooked in these schemes – a factor which may be limiting their success. Our study characterises and quantifies the phenology of nectar resources at the whole‐farm scale on replicate farms in Southwestern UK throughout the flowering season. We quantify the corresponding nectar demands of a subset of common wild pollinators (bumblebees) to compare nectar supply and pollinator demand throughout the year, thereby identifying periods of supply‐demand deficit. We record strong seasonal fluctuations in farmland nectar supplies, with two main peaks of nectar production (May and July) and a considerable 'June Gap' in‐between. March and August/September are also periods of low nectar availability. Comparing the phenology of nectar supply with the phenology of bumblebee nectar demand reveals 'hunger gaps' during March and much of August/September when supply is unlikely to meet demand. Permanent pasture and woodland produced the greatest share of farmland nectar because of their large area, however linear features such as hedgerows and field margins provided the greatest nectar per unit area. 50% of total nectar was supplied by just three species (Allium ursinum, Cirsium arvense and Trifolium repens), but some less productive species (e.g. Hedera helix and Taraxacum agg.) were important in ensuring phenological continuity of nectar supply. Synthesis and applications. By comparing the phenology of farmland nectar supply with the phenology of pollinator demand, we demonstrate that the timing of nectar supply may be as important as total nectar production in limiting farmland pollinator populations. Considering phenology in the design of agri‐environment or restoration schemes is therefore likely to improve their suitability for pollinators. Plant species which flower during periods of resource deficit (early spring and late summer) should be prioritised in schemes which aim to conserve or restore pollinator populations. Maintaining a range of semi‐natural habitats with complementary flowering phenologies (e.g. woodland, hedgerows and field‐margins) will ensure a more continuous supply of nectar on farmland, thereby supporting pollinators for their entire flight season.

opencc-zeroNov 2019View details →

Data from: Sulfoxaflor exposure reduces egg laying in bumblebees (Bombus terrestris)

<ol> <li>Sulfoximine-based insecticides, such as sulfoxaflor, are of increasing global importance and have been registered for use in 81 countries, offering a potential alternative to neonicotinoid insecticides.</li> <li> Previous studies have demonstrated that sulfoxaflor exposure can have a negative impact on the reproductive output of bumblebee colonies, but the specific life-history variables that underlie these effects remain unknown.</li> <li>Here, we used a microcolony-based protocol to assess the sub-lethal effects of chronic sulfoxaflor exposure on egg laying, larval production, ovary development, sucrose consumption, and mortality in bumblebees. Following a pre-registered design, we exposed colonies to sucrose solutions containing 0, 5, 10 and 250ppb of sulfoxaflor. Exposure at 5ppb has been previously shown to negatively impact colony reproductive success.</li> <li>Our results showed that sulfoxaflor exposure at 5ppb (lowest exposure tested) reduced the number of eggs found within the microcolonies (Hedge's d = -0.37), with exposed microcolonies also less likely to produce larvae (Hedge's d = -0.36). Despite this, we found no effect of sulfoxaflor exposure on ovarian development. Sulfoxaflor-exposed bumblebees consumed less sucrose solution, potentially driving the observed reduction in egg laying.</li> <li> Policy implications. Regulatory bodies such as the European Food Safety Authority (EFSA) are under increasing pressure to consider the potential impact of insecticides on wild bees, such as bumblebees, but sublethal effects can go undetected at lower-tier testing. In identifying just such an effect for bumblebees exposed to sulfoxaflor, this study highlights that microcolony-based protocols are a useful tool that could be implemented within an ecotoxicology framework. Furthermore, the results provide evidence for potentially negative consequences of pollinator exposure to an insecticide that is currently undergoing the licensing process in several EU member states.</li> </ol>

opencc-zeroSep 2019View details →

Data from: Risk of potential pesticide use to honeybee and bumblebee survival and distribution: a country-wide analysis for The Netherlands

Aim: Bees play an important role in natural ecosystems and the world's food supply. In the past decades, bee abundance and diversity have declined globally. This has resulted in decreased pollination services for natural ecosystems and the agricultural sector at the field scale. One of the causes of the decline in bee abundance and diversity is the use of pesticides. Linking pesticide use, land use and bee presence could provide crucial insights into areas and pesticides that pose a significant threat to the abundance and diversity of bees. Obtaining actual figures of farmer pesticide use is rarely possible. Therefore, we designed a method to study the effects of potential pesticide use on the survival and distribution of honey- and bumblebees. Location: The Netherlands. Methods: A pesticide risk model was implemented incorporating a hazard quotient as the risk assessment. The number of allowed pesticide active ingredients per crop that could pose a risk to honeybees and bumblebees were linked to the Dutch crop parcel locations for 2015 and 2016. The potential pesticide risk maps were analyzed using honeybee colony survival and bumblebee presence data. Results: Non-significant negative effects of potential pesticide risk on honeybee colony survival and bumblebee presence were found. A significant negative effect of greenhouses was identified for both honeybees and bumblebees. The most important factors in the models predicting honeybee colony survival and bumblebee presence were urban land areas and natural grasslands respectively, both showing a positive effect. Main conclusions: Here, the first attempt to estimate and map pesticide risk to bees in the Netherlands in a country-wide manner is presented. The results could provide crucial high-resolution insights for bee conservation action and facilitate the increase of pollination services in natural ecosystems and the agricultural sector on a local and country-wide scale.

opencc-zeroDec 2017View details →

Data from: A pollen fatty acid enhances learning and survival in bumblebees

Learning associations between food-related stimuli and nutrients allows foragers to collect resources efficiently. In turn, the nutrients foragers consume can themselves affect learning performance, through innate preferences for pre-ingestive stimuli, as well as post-ingestive reinforcement. Bees are insect models of learning and memory, yet the vast majority of this research concerns nectar (carbohydrate) rather than pollen (protein/lipid) rewards, despite the fact that many bees collect both simultaneously. We asked how one component of pollen surface chemistry, a free fatty acid (oleic acid), affected bees' performance in a nectar-learning task. We found that ingestion of oleic acid enhanced visual learning, likely through positive post-ingestive reinforcement. This was supported by our finding that although bees did not prefer to consume the oleic acid solution, its ingestion both decreased motor activity and increased survival. These results are a step towards understanding how nutritionally complex floral rewards may affect cognitive processes that underlie pollination mutualisms.

opencc-zeroJul 2019View details →

Data from: Pattern of population structuring between Belgian and Estonian bumblebees

Several population genetic studies investigated the extent of gene flow and population connectivity in bumblebees. In general, no restriction in gene flow is considered for mainland populations of common bumblebee species. Whether this assumption holds true for all species is not known. An assessment of bumblebee genetic structure in the context of their geographic distribution is needed to prioritize conservation and management needs. Here, we conducted a genetic study on seven bumblebee species occurring in Belgium and Estonia. Using 16 microsatellite markers, we investigated genetic diversity and population structuring in each species. This is the first study investigating population structuring of both declining and stable bumblebee species on both small and large geographic scales. Our results showed no or only low population structuring between the populations of the restricted and declining bumblebee species on both scales, while significant structuring was found for populations of the common species on the larger scale. The latter result, which may be due to human or environmental changes in the landscape, implies the need for the conservation of also widespread bumblebee species. Conservation strategies to improve gene flow and connectivity of populations could avoid the isolation and future losses of populations of these important species.

opencc-zeroFeb 2020View details →

Insecticide exposure during brood or early-adult development reduces brain growth and impairs adult learning in bumblebees

For social bees, an understudied step in evaluating pesticide risk is how contaminated food entering colonies affects residing offspring development and maturation. For instance, neurotoxic insecticide compounds in food could affect central nervous system development predisposing individuals to become poorer task performers later-in-life. Studying bumblebee colonies provisioned with neonicotinoid spiked nectar substitute, we measured brain volume and learning behaviour of 3 or 12-day old adults that had experienced in-hive exposure during brood and/or early-stage adult development. Micro-computed tomography (µCT) scanning and segmentation of multiple brain neuropils showed exposure during either developmental stage caused reduced mushroom body calycal growth relative to unexposed workers. Associated with this, was a lower probability of responding to a sucrose reward and lower learning performance in an olfactory conditioning test. Whilst calycal volume of control workers positively correlated with learning score, this relationship was absent for exposed workers indicating neuropil functional impairment. Comparison of 3 and 12-day adults exposed during brood development showed a similar degree of reduced calycal volume and impaired behaviour highlighting lasting and irrecoverable effects from exposure despite no adult exposure. Our findings help explain how the onset of pesticide exposure to whole colonies can lead to lag-effects on growth and resultant dysfunction.

opencc-zeroMay 2020View details →

No evidence for neonicotinoid preferences in the bumblebee Bombus impatiens

Neonicotinoid pesticides can have a multitude of negative sub-lethal effects on bees. Understanding their impact on wild populations requires accurately estimating the dosages bees encounter under natural conditions. This is complicated by the possibility that bees might influence their own exposure: two recent studies found that bumblebees (Bombus terrestris) preferentially consumed neonicotinoid-contaminated nectar, even though these chemicals are thought to be tasteless and odourless. Here we used Bombus impatiens to explore two elements of these reported preferences, with the aim of understanding their ecological implication and underlying mechanism. First, we asked whether preferences persisted across a range of realistic nectar sugar concentrations, when measured at a series of time points up until 24 hours. Second, we tested whether bees' neonicotinoid preferences were driven by an ability to associate their post-ingestive consequences with floral stimuli such as color, location, or scent. We found no evidence that foragers preferred to consume neonicotinoid-containing solutions, despite finding effects on feeding motivation and locomotor activity in line with previous work. Bees also did not preferentially visit floral stimuli previously paired with a neonicotinoid-containing solution. These results highlight the need for further research into the mechanisms underlying bees' responses to these pesticides, critical for determining how neonicotinoid-driven foraging preferences might operate in the real world for different bee species.

opencc-zeroDec 2014View details →

Data from: Targeted agri-environment schemes significantly improve the population size of common farmland bumblebee species

Changes in agricultural practice across Europe and North America have been associated with range contractions and local extinction of bumblebees (Bombus spp.). A number of agri-environment schemes have been implemented to halt and reverse these declines, predominantly revolving around the provision of additional forage plants. Although it has been demonstrated that these schemes can attract substantial numbers of foraging bumblebees, it remains unclear to what extent they actually increase bumblebee populations. We used standardized transect walks and molecular techniques to compare the size of bumblebee populations between Higher Level Stewardship (HLS) farms implementing pollinator-friendly schemes and Entry Level Stewardship (ELS) control farms. Bumblebee abundance on the transect walks was significantly higher on HLS farms than ELS farms. Molecular analysis suggested maximum foraging ranges of 566 m for Bombus hortorum, 714 m for B. lapidarius, 363 m for B. pascuorum and 799 m for B. terrestris. Substantial differences in maximum foraging range were found within bumblebee species between farm types. Accounting for foraging range differences, B. hortorum (47 vs 13 nests/km2) and B. lapidarius (45 vs 22 nests/km2) were found to nest at significantly greater densities on HLS farms than ELS farms. There were no significant differences between farm type for B. terrestris (88 vs 38 nests/km2) and B. pascuorum (32 vs 39 nests/km2). Across all bumblebee species, HLS management had a significantly positive effect on bumblebee nest density. These results show that targeted agri-environment schemes that increase the availability of suitable forage can significantly increase the size of wild bumblebee populations.

opencc-zeroDec 2011View details →

Data from: Parental frequencies and spatial configuration shape bumblebee behavior and floral isolation in hybridizing Rhinanthus

To shed light on the role played by pollinators in the diversification of angiosperms, focus is needed on how floral isolation varies locally in the early stages of plant divergence. The few studies performed so far have often used species pairs with distinct pollination syndromes and contrasting floral displays. Here, we focus on a hybridizing pair (Rhinanthus minor and R. angustifolius) with strong similarities in flower morphology and pollinators (bumblebees). We examined how ethological isolation changes locally in relation to relative Rhinanthus frequencies, spatial configurations, and pollinator assemblages. Interestingly, floral divergence based on adaptation to different pollinators is unlikely in Rhinanthus: no relationship was found between floral isolation and the local pollinator assemblage. In contrast, species frequency and spatial arrangement strongly influenced bumblebee behavior, ethological isolation, and thus potentially hybrid formation. When both Rhinanthus were present in equal proportions, bees generally preferred the more rewarding and conspicuous species. However, when the Rhinanthus frequencies were unbalanced, the more abundant species was preferred, although this was less pronounced when the less rewarding R. minor predominated. Ethological isolation is highly sensitive to site characteristics, and can be as high as in species with contrasting floral displays and pollinator suites, even though flowers are similar.

opencc-zeroDec 2014View details →

Data from: Climate change impacts on bumblebees converge across continents

For many species, geographical ranges are expanding toward the poles in response to climate change, while remaining stable along range edges nearest the equator. Using long-term observations across Europe and North America over 110 years, we tested for climate change–related range shifts in bumblebee species across the full extents of their latitudinal and thermal limits and movements along elevation gradients. We found cross-continentally consistent trends in failures to track warming through time at species' northern range limits, range losses from southern range limits, and shifts to higher elevations among southern species. These effects are independent of changing land uses or pesticide applications and underscore the need to test for climate impacts at both leading and trailing latitudinal and thermal limits for species.

FIGURE 74 in Early-diverging bumblebees from across the roof of the world: the high-mountain subgenus Mendacibombus revised from species' gene coalescents and morphology (Hymenoptera, Apidae)

FIGURE 74. Map of richness in indigenous species of all bumblebees excluding the subgenus Mendacibombus among equalarea grid cells. Map, grid, and grey scale as in Figs 71, 72.

FIGURE 68 in Early-diverging bumblebees from across the roof of the world: the high-mountain subgenus Mendacibombus revised from species' gene coalescents and morphology (Hymenoptera, Apidae)

FIGURE 68. Best estimate of phylogeny and absolute chronogram for the species of the subgenus Mendacibombus (as recognised in Figs 11, 12), from a linked-tree BEAST analysis of COI, 16S, PEPCK and opsin genes. Values above nodes of the maximum clade-credibility tree are Bayesian posterior probabilities showing branch support. Numbers below nodes are the estimated ages of events in Ma (millions of years before the present) based on the Mendacibombus root-date estimate of 34 (25–40) Ma from Hines (2008). The grey bars represent the 95% confidence intervals for the estimates of the age of events.

FIGURES 56‒67 in Early-diverging bumblebees from across the roof of the world: the high-mountain subgenus Mendacibombus revised from species' gene coalescents and morphology (Hymenoptera, Apidae)

FIGURES 56‒67. Maps of the global distributions of species of the subgenus Mendacibombus from the material examined, with grey spots for specimen records and black spots for the samples with COI sequences (each species is unknown from regions outside the map boundaries shown); grey crosses for records of all species of Mendacibombus combined. Relief map with hill shading, Cartesian orthonormal projection, grey lines show borders to national administration according to UN maps, north at the top of the map. Image created in ArcGIS using World_Shaded_Relief basemap © 2014 Esri.

FIGURES 69‒70 in Early-diverging bumblebees from across the roof of the world: the high-mountain subgenus Mendacibombus revised from species' gene coalescents and morphology (Hymenoptera, Apidae)

FIGURES 69‒70. Photos of (69) a worker of B. superbus (MD#4123) from (left) the dorsal and (right) the left lateral aspect (scale bar 10 mm), from the sample site (70) in the Tanggula mountains, Xizang, China (16.viii.2014, 32.86142°N 91.91739°E, GPS elevation ca 5220 m). Photos by (69) NHM digital imaging unit and (70) Z.-Y. Miao.

FIGURES 11‒12 in Early-diverging bumblebees from across the roof of the world: the high-mountain subgenus Mendacibombus revised from species' gene coalescents and morphology (Hymenoptera, Apidae)

FIGURES 11‒12. Recognising species from an estimate of phylogeny for 30 unique COI haplotypes of the subgenus Mendacibombus by BEAST, using GMYC models and the PTP procedure. From the GMYC models (11), the single threshold T is shown by the vertical grey bar so that the intersecting lineages are interpreted as indicating 12 separate species (black spots at coalescent nodes; outgroups not shown). Values below the nodes of the maximum clade-credibility tree are Bayesian posterior probabilities showing branch support (groups with values <0.8 are considered unreliable) from the BEAST analysis with two billion MCMC generations and a 1% burn-in. The x-scale axis is calibrated in substitutions per nucleotide site. From the PTP procedure (12), the Bayesian PTP solution with highest support also indicates 12 species. Values above the nodes are PTP Bayesian support values that all daughter haplotypes are parts of a single species; values below the nodes are Bayesian posterior probabilities showing branch support. The scale bar is calibrated in substitutions per nucleotide site. Each unique haplotype is represented by one of the longest available sample sequences, labelled with: the sequence length in number of base pairs, a taxon name or name for an unpublished colour pattern (light/dark/yellow/white/pale), and then a code that consists of a specimen identifier (MD#) from the project database and (after the hyphen) a sample identifier from BOLD or from GenBank, followed with its geographic origin.