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Bumblebees are undergoing strong declines in Europe caused by habitat loss and fragmentation, agricultural intensification, and climate change. Long-term records are necessary to estimate population trends precisely and to propose appropriate mitigation strategies. Based on an original database of 173,788 specimens from museum collections, scientific monitoring, and opportunistic citizen data from 1810 to 2016, we compared changes in species richness and area of occupancy of Belgian bumblebee species through three time-periods (1910–1930, 1970–1989, and 1990–2016). We also assessed if the observed trends are related to species-specific ecological traits and spatial scales (local, regional and national). Overall, species richness decreased over the last century in Belgium, but some regions retained relatively species-rich communities. A strong shift in community composition occurred. Three species remained among the "top five" in terms of species occurrence (area of occupancy) between the three time-periods (B. pascuorum, B. lapidarius, and B. pratorum), but several species that were once widespread declined drastically (B. muscorum, B. humilis, B. ruderatus, and B. veteranus), while a few species increased their distribution (e.g. B. hypnorum and B. terrestris). Habitat preferences significantly explained the observed trends, with declining species preferring open habitats and increasing species preferring wooded habitats. [ABSTRACT FROM AUTHOR]

Sexual dimorphism is a pervasive form of variation within species. Understanding how and why sexual dimorphism evolves would contribute to elucidating the mechanisms underlying the diversification of traits. In flowering plants, pollinators are considered a driver of sexual dimorphism when they affect female and male plant fitness in distinct ways. Here, we found that flowers appear to manipulate the behavior of pollinators using sexually dimorphic traits in the dioecious tree Eurya japonica. In this plant, female flowers present a higher-quality reward for pollinators, whereas male flowers have a more conspicuous appearance. Plants benefit by inducing pollinators to carry pollen from male to female flowers, and their sexual dimorphism might thus facilitate pollen movement through pollinator behavior. In two-choice experiments, pollinators frequently moved from male to female flowers, whereas computer simulation suggested that sexually dimorphic traits would evolve if pollinators changed behavior depending on the traits of the flowers they had just visited. These results suggest that the floral traits affecting the visiting order of pollinators have evolved in plants. Using E. japonica, we theoretically show that the induction of sequential behavior in pollinators might be crucial to the evolution of sexual dimorphism in flowers, and our experiments support these findings. [ABSTRACT FROM AUTHOR]

The abundance of both flower-visiting insects and flowering plants in semi-natural grasslands in temperate zones has declined as a result of overbrowsing by deer. The construction of deer fences is an effective method for biodiversity conservation because these fences prevent the invasion of deer. However, few studies have elucidated the biodiversity conservation effects of deer fences in semi-natural grasslands. Here we investigated the effects of the construction of deer fences on the diversity of butterflies, bumblebees, and flowering plants on the Kirigamine Plateau, Nagano Prefecture, Japan, which is covered by semi-natural grassland. The number of species of flowering plants inside the deer fences was higher than that outside the deer fences. The numbers of individuals and species of flower-visiting butterflies and bumblebees also tended to be higher inside the deer fences than outside the deer fences. On the other hand, there tended to be no difference in the number of individuals and species of non-flower-visiting butterflies inside and outside the deer fences. The diversity of flowering plants, butterflies, and bumblebees within the fenced areas was not substantially affected by the size of the fenced-off area. Our findings suggested that the construction of deer fences can contribute to the conservation of both flower-visiting insects and flowering plants in semi-natural grassland. [ABSTRACT FROM AUTHOR]

Differential visitation of pollinators due to divergent floral traits can lead to reproductive isolation via assortative pollen flow, which may ultimately be a driving force in plant speciation, particularly in areas of overlap. We evaluate the effects of pollinator behavioral responses to variation of intraspecific floral color and nectar rewards, on reproductive isolation between two hybrid flower color morphs (fuchsia and blue) and their parental species Penstemon roseus and P. gentianoides with a mixed-pollination system. We show that pollinators (bumblebees and hummingbirds) exhibit different behavioral responses to fuchsia and blue morphs, which could result from differential attraction or deterrence. In addition to differences in color (spectral reflectance), we found that plants with fuchsia flowers produced more and larger flowers, produced more nectar and were more visited by pollinators than those with blue flowers. These differences influenced the foraging behavior and effectiveness as pollinators of both bumblebees and hummingbirds, which contributed to reproductive isolation between the two hybrid flower color morphs and parental species. This study demonstrates how differentiation of pollination traits promotes the formation of hybrid zones leading to pollinator shifts and reproductive isolation. While phenotypic traits of fuchsia and red flowers might encourage more efficient hummingbird pollination in a mixed-pollination system, the costs of bumblebee pollination on plant reproduction could be the drivers for the repeated shifts from bumblebee- to hummingbird-mediated pollination. [ABSTRACT FROM AUTHOR]

Bumblebees are important pollinating insects, but many species have suffered declines over the last century. Long-tongued bumblebees have been identified as particularly at risk, partly due to their more selective diet. Attempts to study these species in captivity have been impeded by stress-induced behaviours which cause queens to kill or abandon their brood. Here, we attempt to further develop techniques, using queen pairing and Bombus terrestris cocoons, to successfully rear two common long-tongued bumblebee species (B. pascuorum and B. hortorum) in captivity. Approximately half of queens laid eggs and 29% produced workers. Although challenges remain, there is a great deal to be gained from optimising the captive rearing of these species. [ABSTRACT FROM AUTHOR]

Bumblebees exposed to neonicotinoid pesticides collect less pollen on foraging trips. Exposed bumblebees are also slower to learn to handle flowers, which may account for reduced pollen collection. It is unclear, however, why neonicotinoid exposure slows learning to handle flowers. We investigated the effect of imidacloprid, a neonicotinoid pesticide, on bumblebee motor learning using a lab model of flower handling. Bumblebees learned to invert inside a narrow tube and lift a petal-shaped barrier to reach a reward chamber. Imidacloprid-exposed bumblebees showed a dose-dependent delay to solve the task, which resulted from reduced switching between behavioural strategies and a subsequent delay in use of the successful strategy. This effect was consistent in colonies exposed at 10 but not 2.6 ppb, suggesting a variable effect on individuals at lower doses. These results help to explain why exposed bumblebees are slow to learn to handle flowers and collect less pollen on foraging trips. [ABSTRACT FROM AUTHOR]

Pollinator decline worldwide is well-documented; globally, chemical pesticides (especially the class of pesticides known as neonicotinoids) have been implicated in hymenopteran decline, but the mechanics and drivers of population trends and dynamics of wild bees is poorly understood. Declines and shifts in community composition of bumble bees (Bombus spp.) have been documented in North America and Europe, with a suite of lethal and sub-lethal effects of pesticides on bumble bee populations documented. We employ a mathematical model parameterized with values taken from the literature that uses differential equations to track bumble bee populations through time in order to attain a better understanding of toxicant effects on a developing colony of bumble bees. We use a delay differential equation (DDE) model, which requires fewer parameter estimations than agent-based models while affording us the ability to explicitly describe the effect of larval incubation and colony history on population outcomes. We explore how both lethal and sublethal effects such as reduced foraging ability may combine to affect population outcomes, and discuss the implications for the protection and conservation of ecosystem services. [ABSTRACT FROM AUTHOR]

In species distribution modelling, records of species presence are often modelled as a realization of a spatial point process whose intensity is a function of environmental covariates. One way to fit a spatial point process model is to apply logistic regression to an artificial case–control sample consisting of the observed presence records combined with a simulated pattern of background points, usually a uniform random sample from within the study's spatial domain. In this paper we propose local background sampling as an alternative to uniform background sampling when using logistic regression to fit spatial point process models to data. Our method is similar to the local case–control sampling procedure of Fithian and Hastie (Ann Appl Stat 42:1693–1724, 2014), but differs in that background points are sampled with probability proportional to an initial intensity estimate based on a pilot point process model. We compare local background sampling with uniform background sampling in a simulation study and in an example modelling the distributions of bumble bees (genus Bombus) in Ontario, Canada. Our results show local background sampling to be more efficient than uniform background sampling in all simulated settings and across all species analysed. Supplementary materials accompanying this paper appear online. [ABSTRACT FROM AUTHOR]

Bumble bees are declining worldwide, their vital ecosystem services are diminishing and underlying mechanisms are species specific and multifaceted. This has sparked an increase in long-term assessments of historical collections that provide valuable information about population trends and shifts in distributions. However, museums specimens also contain important ecological information, including rarely measured morphological traits. Trait-based assessments of museums specimens provide additional information on underlying mechanisms of population trends, by tracking changes over time. Here, we used museum specimens of four Bombus species, spanning a timeframe of 125 years to: (i) compare body size of declining and increasing species, (ii) assess intra-specific trends over the last century, and (iii) investigate shifts in geographical distribution over time. We found that declining Bombus species were larger than increasing ones. All four species were smaller in current time than a century ago. Intra-specific size declines were more pronounced for larger-bodied species. With our sampling, declining and increasing species showed an upward shift in elevation, and declining species showed an additional geographic shift in recent times as compared to historic records. Intra-specific body size declines may represent species adaptation to unfavorable environmental conditions, and may be a useful metric to complement traditional species vulnerability assessments. We highlight the utility of incorporating trait-based assessments into future studies investigating species declines. [ABSTRACT FROM AUTHOR]

The bumblebee wax moth, Aphomia sociella, is a parasite of bumblebees. In this species, males produce sexual pheromone to attract females, while females produce an aphrodisiac pheromone that initiates male courtship. Both pheromones contain 6,10,14-trimethylpentadecan-2-one (TMPD-one) and the corresponding alcohol, 6,10,14-trimethylpentadecan-2-ol (TMPD-ol) in sex specific quantities. Male sex pheromone consists of 7 components with TMPD-one as a minor one and traces of TMPD-ol. In female aphrodisiac pheromone, TMPD-ol is the major component, while TMPD-one is present in traces. Here we report on the absolute configuration of TMPD-one in male sex pheromone and TMPD-ol in female aphrodisiac pheromone of A. sociella. The configuration was determined from GC/MS of prepared (S)-acetoxypropionyl esters of TMPD-ol. TMPD-one was first reduced to the alcohol that was then derivatized with (S)-acetoxypropionyl chloride. The GC/MS data of obtained diastereoisomers were compared with synthetic standards. The absolute configuration of TMPD-one in the male pheromone was (6R,10R). The configuration of TMPD-ol in the female pheromone was (2R,6R,10R). Electrophysiological experiments showed that TMPD-one and TMPD-ol are perceived by both sexes. The synthetic standards of naturally produced stereoisomers elicited higher responses than mixtures of all stereoisomers. [ABSTRACT FROM AUTHOR]

High-severity wildfires, which can homogenize floral communities, are becoming more common relative to historic mixed-severity fire regimes in the Northern Rockies of the U.S. High-severity wildfire could negatively affect bumble bees, which are typically diet generalists, if floral species of inadequate pollen quality dominate the landscape post-burn. High-severity wildfires often require more time to return to pre-burn vegetation composition, and thus, effects of high-severity burns may persist past initial impacts. We investigated how wildfire severity (mixed- vs. high-severity) and time-since-burn affected available floral pollen quality, corbicular pollen quality, and bumble bee nutrition using percent nitrogen as a proxy for pollen quality and bumble bee nutrition. We found that community-weighted mean floral pollen nitrogen, corbicular pollen nitrogen, and bumble bee nitrogen were greater on average by 0.82%N, 0.60%N, and 1.16%N, respectively, in mixed-severity burns. This pattern of enhanced floral pollen nitrogen in mixed-severity burns was likely driven by the floral community, as community-weighted mean floral pollen percent nitrogen explained 87.4% of deviance in floral community composition. Only bee percent nitrogen varied with time-since-burn, increasing by 0.33%N per year. If these patterns persist across systems, our findings suggest that although wildfire is an essential ecosystem process, there are negative early successional impacts of high-severity wildfires on bumble bees and potentially on other pollen-dependent organisms via reductions in available pollen quality and nutrition. This work examines a previously unexplored pathway for how disturbances can influence native bee success via altering the nutritional landscape of pollen. [ABSTRACT FROM AUTHOR]

Honeybees (Apis mellifera) and bumblebees (Bombus spp.) often undergo exploitative competition for shared floral resources, which can alter their foraging behaviour and flower choice, even causing competitive exclusion. This may be strongest in summer, when foraging conditions are most challenging for bees, compared to other times of the year. However, the seasonal dynamics of competition between these major pollinator groups are not well understood. Here, we investigate whether the strength of exploitative competition for nectar between honeybees and bumblebees varies seasonally, and whether competitive pressure is greatest in summer months. We carried out experimental bee exclusion trials from May to late September, using experimental patches of lavender, variety Grosso, in full bloom. In each trial, we compared the numbers of honeybees (HB) foraging on patches from which bumblebees had been manually excluded (bumblebee excluded, BBE) versus control (CON) patches, HB(BBE-CON). This measure of exploitative competition varied significantly with season. As expected, mean HB(BBE-CON) was significantly greater in summer trials than in spring or autumn trials. This was despite high nectar standing crop volumes in BBE patch flowers in spring and autumn trials. Mean HB(BBE-CON) was not different between spring and autumn trials. Our results show that nectar competition between honeybees and bumblebees varies seasonally and is stronger in summer than spring or autumn, adding to current understanding of the seasonality of resource demand and competition between bee species. This information may also help to inform conservation programs aiming to increase floral resources for bees by showing when these resources are most needed. [ABSTRACT FROM AUTHOR]

In an enclosed glasshouse with sucrose provisioned artificial flowers, we observed nectar-foraging bumble bees and honey bees under several resource conditions to determine potential for displacement. Different responses were displayed for varying resource treatments. Overall, bumble bees did not show reduced foraging in the presence of honey bees. When resources were reduced, bumble bees did not change their foraging behavior, whereas honey bees responded by decreasing their visitation rate. When a food resource of higher quality was introduced, bumble bee foragers shifted their foraging effort to the high-quality resources, whereas honey bees continued to forage on the lower quality resources they had been foraging on. We discuss these results by considering how the individual strategy of bumble bees compared with the colony-based strategy of honey bees may explain observed differences and highlight the potential advantages of each strategy in the natural environment. [ABSTRACT FROM AUTHOR]

The reduction of bumblebee populations has been reported in the last decades, and the microsporidian parasite Nosema bombi is considered as one of the factors contributing to such reduction. Although the decline of bee populations affects both wild plants and human food supply, the effects of Nosema spp. infections are not known because it is difficult to obtain infective spores from wild bees due to their low prevalence. Microscopical observation of fecal samples or midgut homogenates and/or PCR are generally used for N. bombi detection. However, the germination rate of microsporidian spore declines if they are kept at 4 °C for a long time or frozen. It is therefore crucial to minimize the diagnosis and isolation time of infective spores from field-collected samples. Therefore, we performed a loop-mediated isothermal amplification (LAMP) assay for the direct detection of N. bombi in bumblebee midgut homogenates. Using this method, we could detect N. bombi from individuals from which it was visible under the microscope and directly from wild individuals. [ABSTRACT FROM AUTHOR]

We compare four honeybee and one bumblebee species with similar behaviors and ecological requirements but large differences in body size. The bees show allometric brain-body size relationships and scaling exponents similar to those found in vertebrates. Compared with three Asian honeybee species, the European honeybee Apis mellifera feature larger brains than expected for their body mass. Overall, the brains show moderate regional variation across species with two pronounced differences: A. dorsata have an enlarged visual lamina, possibly an adaptation for crepuscular vision. Second, the mushroom bodies are larger and comprise more intrinsic neurons in bumblebees than in honeybees. While these findings might suggest more advanced sensory associations in bumblebees, it is currently not possible to test this notion in the absence of quantitative and comprehensive behavioral comparisons across bee species. [ABSTRACT FROM AUTHOR]

The Iberian Peninsula is known to have acted as a glacial refugium for many species during the Pleistocene in Europe. Several phylogeographical studies have been carried out within the genus Bombus which indicate a genetic differentiation of some of its species in the southern European peninsulas. Bombus lucorum (Linnaeus, 1761) is one of the three cryptic species belonging to the B. lucorum complex. In recent years, this complex has been widely studied; however, there is a lack of information about the genetic diversity of this species and its possible postglacial recolonization events. To overcome this knowledge gap, in this study several populations from the centre of the Iberian Peninsula to Belgium have been characterized using mitochondrial and nuclear markers (cox1 barcoding and 11 microsatellite loci) and the geometric morphometrics of the wings. Results from cox1 indicate a genetic differentiation of the population of Sierra de Guadarrama at the centre of the Iberian Peninsula, while microsatellite loci and geometric morphometrics analyses do not show any population structure. These results point to a past event of genetic differentiation of B. lucorum in the Iberian Peninsula although they also suggest a current gene flow with populations from mainland Europe. [ABSTRACT FROM AUTHOR]

For bumble bees and other social organisms, colonies are the functional unit of the population rather than the individual workers. Estimates of bumble bee nest density are thus critical for understanding population distribution and trends of this important pollinator group. Yet, surveys of bumble bee nests and other taxa with sessile life stages rarely account for imperfect detection. Here, we demonstrate the use of mark-recapture methods to estimate the density of bumble bee nests at multiple sites using standardized survey protocols. We detected ~ 30% of nests in a 2-h survey of each 3000 m2 plot. We determined that 4–5 visits were sufficient to estimate the total number of nests at our site with reasonable precision, equating to one-third the effort previously assumed necessary to reliably estimate nest density. Mark-recapture approaches can be used to generate unbiased estimates of density with reduced search effort, while simultaneously increasing the rate at which nests are discovered. [ABSTRACT FROM AUTHOR]

Governmental agri-environment schemes (AES) aim to improve pollinator abundance and diversity on farmland by sowing wildflower seed mixes. These often contain high proportions of Fabaceae, particularly Trifolium (clovers), which are attractive to some bumblebee species, but not to most of the ~ 240 solitary bee species in the UK. Here we identify wildflowers that are attractive to a greater range of wild bee species. Forty-five wildflower species being farmed for commercial seed production on a single farm were surveyed for native bees. Bee walks were conducted through discrete wildflower areas from April until August in 2018. The results indicate that including a range of Apiaceae, Asteraceae, and Geraniaceae in seed mixes would cater for a wide diversity of bee species. A total of 14 wildflower species across nine families attracted 37 out of the 40 bee species recorded on the farm, and accounted for 99.7% of all visitations. Only two of these 14 species are included in current AES pollinator mixes. Unexpectedly, few visits were made by bumblebees to Trifolium spp. (0.5%), despite their being considered an important food source for bumblebees, while Anthyllis vulneraria and Geranium pratense were highly attractive. For solitary bees, Crepis capillaris, Sinapsis arvensis, Convolvulus arvensis and Chaerophyllum temulum were amongst the best performing species, none of which are usually included in sown flower mixes. We suggest that the standard 'pollinator' mixes used in AES might be updated to include some of these wildflower species, and trialled as seed mixes on farmland. [ABSTRACT FROM AUTHOR]

Some bumble bee species are in decline globally. Declines have been attributed to many factors including habitat loss. Habitat is an integral component of any species and should be a central focus of conservation efforts to protect at risk species. However, the habitat of bumble bee species is not fully understood. We conducted a systematic review of the peer-reviewed literature using Web of Science to summarize articles that have described the habitat of bumble bee species. In total, 55 nesting and 10 overwintering habitat studies are described in this review. We described common patterns associated with bumble bee studies including overwintering habitat, landscape type, and ground position. We found that bumble bee nests are more frequently found underground and that studies were biased towards the United Kingdom and agricultural habitats. There are some preferences in nesting and overwintering habitat, but further research is needed to draw any substantial conclusions. Detection of nesting and overwintering site studies may be improved using citizen science initiatives and possibly through employing detection dogs or radio-telemetry. Increasing the detection of nesting and overwintering sites is an important priority to improve our understanding of bumble bee habitat. It is critical that we identify all aspects of bumble bee habitat to ensure the protection, restoration and creation of important resources to ensure their conservation. [ABSTRACT FROM AUTHOR]

As garden plants in urbanized environments provide considerable diverse floral resources to pollinators, the availability of floral resources has changed as a consequence of increasing urbanization. Although pollinators often forage at different sites in response to spatiotemporal variations in floral resources, little is known about the differences in pollinator foraging between urban and nearby natural environments. We monitored the foraging patterns of bumblebees in open and forest habitats in two areas with and without urban gardens with respect to flowering phenology and the availability of floral resources in each habitat. Floral richness in the forest habitat decreased as the season progressed, with a peak in late spring to early summer, whereas floral resources in the open habitat increased late in the season. Thus, floral resources in the open habitat could compensate for seasonal declines in forest floral resources. In the urban area, which contained green gardens, floral richness in the open habitat was much greater than that in the forest habitat. This resulted in a relatively high density of bumblebees in the open habitat in the urban area compared with those in the natural area, which lacked green gardens. Visitation frequency of bumblebees to forest flowers decreased as the floral richness of the open habitat increased. These results suggest that although urban gardens are important foraging sites for pollinators, the high attractiveness of garden flowers reduces pollinator visits to wildflowers in nearby forests. This may result in reduced pollination of native flowers. [ABSTRACT FROM AUTHOR]

We studied pollination ecology of large cardamom (Amomum subulatum) in three altitudinal gradients (1100, 1500, 2000 m) in the Sikkim Himalaya, with the hypothesis that both honey bees (Apis spp.) and bumble bees (Bombus braviceps, B. haemorrhoidalis) contribute to pollination and enhance yield. We placed honey bees colonies in cardamom stands, studied pollination within 50 m radius, 250 m away from it; and under control nets restricting pollinators. Honey bees showed highest number of floral visits (19.24 ± 4.23 per 12 m2) within 50 m than bumble bees (13.87 ± 3.12 per 12 m2). In 250 m stand, bumble bees visits (20.57 ± 5.31 per 12 m2) were higher than honey bees (9.44 ± 2.54 per 12 m2). Pollen removal by honey bees and bumble bees was 30–40% and 50–70% of the total pollen, respectively. Time spent across sites and treatments by honey bees ranged higher (12.87–36.25 s flower−1), than bumble bees (4.60–27.80 s flower−1). Visitation of bees increased with increasing number of cardamom flowers and showed positive correlation (r2 = 0.46–0.55, P < 0.001). Number of capsules per spike, capsule/seed weight, and gross agronomic yield was highest within 50 m, lower in 250 m and lowest in control confirming that honey bees pollinated stand had higher yield. The study also confirmed that both honey bees and bumble bees were pollen collectors and pollination is by-product of their foraging activity on the flowers. This study suggests new insight on contribution of honey bees to large cardamom pollination and further research is needed for pollinators-large cardamom interaction. [ABSTRACT FROM AUTHOR]

The temporal distribution of resources is an important aspect of habitat quality that can substantially impact population success. Although it is widely accepted that floral resources directly influence wild bee population sizes, we lack experimental data evaluating how resource availability affects colony growth via demographic mechanisms. To achieve this, we tracked marked individuals in bumble bee (Bombus vosnesenskii) colonies to evaluate whether worker survival and reproduction responded to experimentally elevated forage early in colony development. Specifically, we assessed the effect of early resource environment on worker and sexual offspring production, and the survival and body size of individual workers. We also assessed whether responses of colonies differed when exposed to higher or lower resource environments at a relatively smaller (~ 10 workers) or larger (~ 20 workers) size. Resource supplementation always resulted in greater total offspring and male production; however, the influence of supplementation on worker production and quality depended on colony size at the start of supplementation. Among colonies that were initially smaller, colonies that were supplemented produced fewer but larger bodied and longer lived workers compared to control counterparts. Among colonies that were initially larger, colonies that were supplemented produced more workers than corresponding controls, but without changes to worker quality. Collectively, these results provide clear experimental evidence that greater resource availability early in colony development increases overall productivity, and indicate that colonies may pursue different allocation strategies in response to the resource environment, investing in more or better workers. [ABSTRACT FROM AUTHOR]

Understanding how different pesticides influence bee health is inhibited by a limited knowledge about the interactions between different compounds to which bees are simultaneously exposed. Although research has demonstrated synergistic effects of some sterol biosynthesis inhibiting (SBI) fungicides on the toxicity of certain insecticides to bees, a high degree of variability exists in the relatively few SBI fungicide-insecticide interactions tested. Furthermore, most research has been conducted on honey bees, Apis mellifera, limiting our understanding of pesticide synergisms in native wild bees. We tested the effects of the SBI fungicides difenoconazole, myclobutanil, and fenhexamid on acute contact toxicity of the insecticides thiamethoxam (neonicotinoid) and bifenthrin (pyrethroid) to the common eastern bumble bee, Bombus impatiens. Based on range-finding trials, we selected a single dosage of each pesticide, with insecticides approximating LD20 values and fungicides approximating their maximum sublethal levels. We found that the triazole SBI fungicide difenoconazole interacted synergistically with bifenthrin, with a maximum synergy ratio of 1.48, while the triazole myclobutanil interacted synergistically with both bifenthrin and thiamethoxam, with maximum synergy ratios of 11.0 and 2.38, respectively. However, the hydroxyanilide SBI fungicide fenhexamid did not exhibit a synergistic effect on either insecticide. Our results suggest that certain SBI fungicides, and potentially those from particular SBI classes, may be particularly harmful to bumble bee health when co-exposure to insecticides occurs, despite their low toxicity when experienced in isolation. [ABSTRACT FROM AUTHOR]

3 caption was published as, Analysis of the effect of time and temperature on bumblebee active fight period for the citizen-collected data covering all of Sweden 2000-2019. B a b Predicted values of the interaction between temperature and species, and B b b year and species. [Extracted from the article]

Reproductive division of labor, a defining feature of social insects, is often regulated by a combination of behavioral and chemical means. It is hypothesized that behavioral interactions play a more important role in regulating reproduction of primitive eusocial species, while pheromones are typically used by large sized, advanced eusocial species. Here we examined if worker reproduction in the primitively eusocial species Bombus impatiens is regulated by brood pheromones. We recently demonstrated that worker egg laying in this species is inhibited by young larvae and triggered by pupae. However, the mechanism by which the brood communicates its presence and whether brood or hunger pheromones are involved remain unknown. We found that workers were behaviorally attracted to pupae over larvae or control in a choice experiment, in line with their reproductive interests. However, odors from larvae or pupae were insufficient to inhibit worker reproduction. We further show that the youngest larvae are particularly vulnerable to starvation, however, despite a slight attraction and fewer eggs laid by workers in the presence of starved compared with fed larvae, these effects were insignificant. Our study demonstrates that workers can differentiate between larvae and pupae, but not between starved and fed larvae based on olfactory information. However, these signals alone do not explain the reduction in worker egg laying previously found. Bumble bee workers may use information from multiple sources or rely solely on behavioral interactions with brood and other females to make decisions about reproduction, in line with their small colony size and simple social organization. [ABSTRACT FROM AUTHOR]

Floral enhancement schemes in agroecosystems are a common method to supplement bee dietary requirements, yet there is little information about how species used in these schemes influence bee physiology and how their nutritional value compares to the floral resources provided by the crop species. Here, we examined the pollen nutritional quality (macronutrient concentrations and protein:lipid ratio) of pumpkin (Cucurbita pepo, Cucurbitaceae), two species commonly used in enhancement schemes, Helianthus annuus (Asteraceae) and Crotalaria juncea (Fabaceae), a multifloral diet and an artificial diet. We tested effects of these diets on physiological characteristics of Bombus impatiens, a generalist pollinator. Bees performed best on real pollen diets, with consumption of C. juncea and multifloral pollen having the most pronounced effects on bee physiology. Our results underscore the importance of considering nutritional quality when selecting plant species for these schemes. [ABSTRACT FROM AUTHOR]

Bumblebees are economically important insects which perform essential pollination tasks in natural and managed ecosystems. Recent research studying Neotropical bumblebee species in Brazil showed a clear decrease in genetic diversity over time in Bombus pauloensis. A new temporal assessment of genetic diversity is needed to know whether this was a location-specific result, or a more general phenomenon. This knowledge is essential to be able to prioritize conservation and management needs. Here, the genetic variability of B. pauloensis populations in Argentina was investigated over time using museum collection specimens from 1933 to 2016, and compared with reanalyzed data from Brazilian populations. Furthermore, specific time series were made for two Argentinean locations, Candelaria and La Plata, and compared with the time series of Porto Alegre (Brazil). All collected specimens were genotyped with 16 microsatellite loci to estimate genetic diversity parameters. Our results showed no drop in either allelic richness or expected heterozygosity over all Argentinean populations. However, a clear drop in genetic diversity was observed in two out of three location-specific time series. This loss of diversity will have negative impacts on population survival, especially over longer periods of time. Furthermore, the use and release of mass-reared specimens of B. pauloensis, which may be inbred and specifically selected for certain commercial but non-adaptive traits, could further diminish the genetic pool. Thus, our result implies the urgent need for regional conservation policies of B. pauloensis in South Brazil and North Argentina. [ABSTRACT FROM AUTHOR]

Understanding animal movement is critical for conservation planning, habitat management, and ecological study. However, our understanding is often limited by methodological constraints. These limitations can be especially problematic in the study of ecologically and economically important pollinators like bumble bees, where several aspects of their biology limit the feasibility of landscape-scale studies. We review the methods available for the study of bumble bee movement ecology, discussing common limitations and tradeoffs among several frequent data sources. We provide recommendations on appropriate use for different life stages and castes, emphasizing where recent methodological advances can help reveal key components of understudied parts of the bumble bee life cycle such as queen movement and dispersal. We emphasize that there is no one correct method and encourage researchers planning studies to carefully consider the data requirements to best address questions of interest. [ABSTRACT FROM AUTHOR]

Agricultural intensification can impact the availability and quality of resources. We analyzed resource use by bumble bees (Bombus spp.), important pollinators of highbush blueberry (Vaccinium corymbosum), collected from conventional highbush blueberry farms, organic highbush blueberry farms, and nearby natural areas in the lower Fraser River valley of British Columbia, Canada. We identified corbicular pollen and measured bee fat content as an indicator of body condition. Bumble bees use non-crop resources, including pollen from plant species not found on farms. Bees from natural areas had higher pollen protein content in corbicular pollen and higher body fat content than those from conventional and organic farms. There was no difference between farm types, and we could not demonstrate a relationship between pollen protein and bee fat content. Our findings illustrate the importance of resource availability throughout agro-ecological landscapes, including not only farms but also off-farm areas. [ABSTRACT FROM AUTHOR]

The invasion of alien pollinators may disturb the local pollination network between plants and native pollinators. However, alien pollinators may be able to coexist with native pollinators if spatiotemporal partitioning of floral resources is possible at the landscape scale. We compared the seasonal patterns of floral choice and habitat use across local habitats (natural coastal grassland, semi-natural grassland and arable field) between alien Bombus terrestris and two major native species, Bombus hypocrita and Bombus deuteronymus, in a coastal area of northern Japan. Although two native species with different morphological characteristics showed specific floral use patterns, that of B. terrestris overlapped with both native species. Short-tongued B. terrestris and B. hypocrita frequently visited Rosa rugosa and Calystegia soldanella flowers that have shallow or open corollas in the coastal grassland. B. terrestris also visited legume flowers with a long-tubed shape at high frequency in both semi-natural and coastal grasslands, as did long-tongued B. deuteronymus despite the difference in morphology. B. terrestris was observed in every habitat type based on the abundance of floral resources. B. terrestris had wide foraging area and changed target flowers flexibly at the landscape scale according to the seasonal changes in floral resources. Because of the spatiotemporally diverse foraging patterns between B. terrestris and native bumblebees, competition for floral resources may not be intensive at the landscape scale owing to the diverse plant communities mixed with natural and non-natural habitats. [ABSTRACT FROM AUTHOR]

Bombus bicoloratus is an important pollinator of wild flowers in the oriental region. We confirmed a total of 451 specimens of B. bicoloratus from China based on DNA sequences from mitochondrial cytochrome oxidase subunit I (COI) barcodes. Bombus bicoloratus is distributed mainly in tropical and subtropical areas of southern China. This species exhibits a striking intraspecific colour-pattern polymorphism both in females and males. The distribution frequency of the different colour patterns is heavily skewed, with 50.9% of the workers sharing the same colour pattern that predominates in most locations. Workers from the islands of Hainan and Taiwan possess a very distinct colour pattern, and its spatial distribution is correlated with the climate factor irradiance. Bombus bicoloratus has been recorded to collect nectar and pollen from 14 plant families, indicating that this species is polylectic. This study will be helpful for recognising bumblebee species with variable colour patterns, especially B. bicoloratus, in Asia. [ABSTRACT FROM AUTHOR]

Like all animals, bees need to consume essential amino acids to maintain their body's protein synthesis. Perception and discrimination of amino acids are, however, still poorly understood in bees (and insects in general). We used chemotactile conditioning of the proboscis extension response (PER) to examine (1) whether Bombus terrestris workers are able to perceive amino acids by means of their antennae and (if so) which ones, (2) whether they are able to differentiate between different amino acids, and (3) whether they are able to differentiate between different concentrations of the same amino acid. We found that workers perceived asparagine, cysteine, hydroxyproline, glutamic acid, lysine, phenylalanine, and serine, but not alanine, leucine, proline, or valine by means of their antennae. Surprisingly, they were unable to differentiate between different (perceivable) amino acids, but they distinguished between different concentrations of lysine. Consequently, bumblebees seem to possess amino acid receptors at the tip of their antennae, which enable a general perception of those solute amino acids that have an additional functional group (besides the common amino and carboxylic groups). They may thus have the ability to assess the overall amino acid content of pollen and nectar prior to ingestion. [ABSTRACT FROM AUTHOR]

Bumblebees Bombus terrestris are good at learning to distinguish between patterned flowers. They can differentiate between flowers that differ only in their patterning of scent, surface texture, temperature, or electrostatic charge, in addition to visual patterns. As recently shown, bumblebees trained to discriminate between nonvisual scent patterns can transfer this learning to visually patterned flowers that show similar spatial patterning to the learnt scent patterns. Bumblebees can, therefore, transfer learnt patterns between different sensory modalities, without needing to relearn them. We used differential conditioning techniques to explore whether cross-modal transfer of learnt patterns also occurred between visual and temperature patterns. Bumblebees that successfully learnt to distinguish rewarding and unrewarding temperature patterns did not show any preferences for the corresponding unlearnt visual pattern. Similarly, bumblebees that learnt visual patterns did not transfer these to temperature patterns, suggesting that they are unable to transfer learning of temperature and visual patterns. We discuss how cross-modality pattern learning may be limited to modalities that have potentially strong neurological links, such as the previously demonstrated transfer between scent and visual patterns. [ABSTRACT FROM AUTHOR]

Many Bumble bee (Bombus) species are in decline and conservation efforts must be undertaken now to lessen or reverse the trend. For effective efforts to occur, the first step must be an accurate assessment of extinction risk. Yet only four of over forty Canadian Bombus species have been assessed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), despite evidence of decline for numerous species in this genus. Here, we evaluated the status of the American Bumble bee, Bombus pensylvanicus De Geer 1773 in Canada. A challenge with species assessments is obtaining adequate occurrence data temporally and spatially. Citizen science is a field where volunteers can collect data similar to that of experts over a broader coverage than researchers could often cover alone. We used data from the Bumble Bee Watch citizen science program, a database of North American Bombus records representing field survey and collection records from the late-1800s, and our own field surveys to evaluate the status of B. pensylvanicus in Canada using the International Union for the Conservation of Nature (IUCN) Red List assessment criteria. We found that B. pensylvanicus' Area of Occurrence has decreased by about 70%, its Extent of Occurrence by 37%, and its relative abundance by 89%, from 2007 to 2016 as compared to 1907–2006. These findings warrant an assessment of Critically Endangered using IUCN Red List criteria for B. pensylvanicus in Canada. Our findings will help inform management of B. pensylvanicus and exemplify the importance of citizen science programs for wildlife conservation. [ABSTRACT FROM AUTHOR]

Bumblebees (Bombus spp.) are declining in most parts of Western Europe. Many studies have highlighted the role of agricultural intensification and urbanisation in this decline, and some have also shown the influence of landscape composition on bumblebee populations. However, very few studies have explored bumblebee communities prior to the onset of these major land use changes, and those studies that do are mostly based on low-resolution spatial data. Here, we perform a comparative analysis based on detailed landscape composition and bumblebee occurrence records between the early twentieth century (1910–1930) and the contemporary period (2013–2015) in four localities representative of Belgium. We show that bumblebee assemblages changed drastically over this period, and that the decline in richness was strongest in areas with the greatest increase in urbanization and agricultural intensification. The one locality still retaining a high proportion of grasslands, orchards and woodlands with the smallest overall change in landscape composition still hosts a rich bumblebee fauna, very similar than in the past. We provide recommendations for land use management based on these findings. We also warn about the importance of other factors such as land use intensity, climatic conditions and altitude, which should be included in any future study addressing changes in bumblebee populations related to land use changes. [ABSTRACT FROM AUTHOR]

The high pollen and nectar yield of Asteraceae flowers combined with the abundance and diversity of these plants should make them an important pollen source for both specialist and generalist bees. However, studies have found Asteraceae pollen to be a poor diet for some generalist bees, possibly owing to nutrient deficiencies or the presence of secondary metabolites or digestive barriers that prevent nutrient assimilation. Mixing pollens could allow bees to exploit these unfavourable pollens, if the different pollen sources help to complement nutrient deficiencies or alleviate the effects of toxic secondary metabolites. In our study, we examined how the proportion of sunflower (Helianthus annuus, Asteraceae) pollen in the diet of captive-reared bumblebees (Bombus impatiens) affects the survival of bees in queenless microcolonies. Bees fed on sunflower pollen had significantly shorter lifespans than bees fed on broad bean (Vicia faba, Fabaceae), rapeseed (Brassica napus, Brassicaceae) or Cucurbitaceae pollen. However, survival on mixed pollen diets containing 50% sunflower pollen was as great as that on non-sunflower diets, which suggests that the other pollens were able to compensate for the low nutritive quality of the sunflower pollen. Due to agricultural intensification and a loss of wildflowers, farmland monocultures (e.g. sunflower crops) can be important floral resources for bumblebees. Our study suggests that providing alternative floral resources of high nutritive quality could help mitigate the potential harmful effects of a monofloral sunflower diet on bumblebees. [ABSTRACT FROM AUTHOR]

Context: Bumblebees are important pollinators for agricultural crops and wild plants. However, agricultural intensification and loss of semi-natural habitat may have adverse effects on colony performance. While mass-flowering crops may serve as food sources, landscapes dominated by intensive agriculture may be a poor bumblebee habitat compared to landscapes dominated by semi-natural habitat, such as forests and species-rich grasslands. Objectives: We investigated the effect of different land use classes on bumblebee colony performance at two periods of time during the flying season. We expected mass-flowering crops to have a positive influence on colony performance during flowering. After mass-flowering, presence of semi-natural habitat was hypothesized to be essential for colony development. Methods: We placed artificial colonies of Bombus terrestris in 28 apple and pear orchards during and after mass-flowering. We measured colony growth and took pollen samples from foraging workers. Causal relationships between land-use, pollen quality, amount of pollen collected and colony performance were analyzed. Results: Contrary to our expectations, we found a negative correlation between orchard cover and amount of pollen collected in spring, during mass-flowering, resulting in a lower colony performance. During mass-flowering, colony performance and pollen diversity were positively correlated with cover of open semi-natural habitat, while after mass-flowering, colony performance was positively correlated with forest cover. After mass-flowering, pollen sources were more diverse and colony growth was related to land use classes at a larger spatial scale, indicating that bumblebees foraged further. We did not find a correlation between the performances of colonies at one specific site that were placed during and after mass-flowering. Conclusions: Landscapes dominated by mass-flowering orchards represent inferior habitats for bumblebees during flowering. Heterogenous landscapes, containing a mix of various types of semi-natural habitat increase the habitat quality for bumblebees. We advise to maintain these diverse patches of semi-natural habitat, as mass-flowering crops alone are insufficient to support bumblebee colonies. [ABSTRACT FROM AUTHOR]

Context: Native pollinators provide an important ecosystem service for many pollination-dependent fruit crops, but require nesting and foraging resources in proximity to target crop plants. Landscape context and fluctuation in floral resources may influence the distribution of pollination services. Objectives: This study investigates how landscape context influences bumble bee density on cranberry marshes across a resource pulse created by the target crop bloom. Methods: We sampled bumble bees at fourteen cranberry marshes before, during, and after the cranberry bloom in central Wisconsin. We quantified floral richness and surrounding land cover and assessed their effects on bumble bee density and colony representation using OLS regression. We measured colony representation as a colony detection rate—where low colony detection means more colonies were represented by single individual foragers. Results: The amount of forest surrounding marshes explained the most variation in colony density, but not colony representation on site. Sites with high meadow interspersion in the surrounding landscape had lower colony representation (i.e., detection rate), suggesting some dilution effect. Colony density and detection did not change between the pre- and post-bloom period and resource pulse, even after statistically controlling for important landscape-scale effects. Yet, relative increase in colony density, was best explained by increased floral richness and decreased open-shrub bog. Landscapes with less clumpy forest experienced increased colony representation during the crop bloom. Conclusions: We suggest maintaining forest within cultivated landscapes to promote local bumble bee colony density, and increasing floral richness on site to attract foraging bees. [ABSTRACT FROM AUTHOR]

Context: Biodiversity monitoring programs require fast, reliable and cost-effective methods for biodiversity assessment in landscapes. Sampling pollinators across entire landscapes is challenging, as trapping needs to cover many habitat types. Objectives: We developed and tested a landscape-wide sampling design for pollinators. We assessed the predictability and stability of pollinator biodiversity estimates in agricultural landscapes, and tested how estimates were affected by sampled habitat, landscape composition and spatial scale. Methods: We sampled pollinators using pan traps at 250 locations in 10 replicated landscapes measuring 1 × 1 km and calculated bee richness predictions based on different sample sizes. Traps were placed regularly in each landscape, sampling each habitat proportionally to its area. Landscapes contained semi-natural habitats, crop fields and forests and differed in the amount of a mass-flowering crop (oilseed rape). Results: Regular sampling reflected local habitat amount. Compared with cereal fields, significantly more pollinators occurred in oilseed rape, and fewer in forests. Sampling in only one habitat type led to biased estimates of landscape-wide bee species richness, even when sample size was increased. The spatial scale of best predictions depended on the sampled habitat. Species richness was overestimated when sampling was limited to semi-natural habitats and underestimated in oilseed rape fields. Precision increased with the number of sampling points per landscape. Conclusions: To study landscape-wide pollinator biodiversity, we suggest to sample multiple sites per landscape in a broad range of resource-providing habitat types, with sample sizes proportional to habitat amount. Our approach will also be useful for biodiversity monitoring programs in general. [ABSTRACT FROM AUTHOR]

The male cephalic labial gland secretions of bumblebees are known to be species-specific semiochemicals. These secretions that are involved in bumblebee pre-mating recognition provide efficient diagnostic characters for species delimitation. The subgenus Thoracobombus is the largest group of bumblebees and is found in the Palearctic, Nearctic, and Neotropical regions. Here, the cephalic labial gland secretion (CLGS) composition of six Mexican Thoracobombus bumblebee species are analyzed: Bombus diligens, B. medius, B. mexicanus, B. pensylvanicus, B. trinominatus, and B. weisi. Our results suggest the presence of two new potential species into the formerly recognized B. weisi as well as one new potential species in the taxon presently identified as B. pensylvanicus. Moreover, the male of B. pensylvanicus, known to congregate at nest sites awaiting the emergence of virgin queens, is characterized by low concentrations of the C16 component. This observation raises the possibility that courtship behavior as well as environmental constraints could affect the role of the male bumblebees' CLGS. [ABSTRACT FROM AUTHOR]

The use of commercial bumblebees to aid crop pollination may result in overcrowding of agricultural landscapes by pollinators. Consequently, transmission of parasites between pollinators via shared flowers may be substantial. In SW Spain, we assessed the initial infection status of commercial Bombus terrestris colonies and then explored spatial and seasonal influences on changes in parasite prevalence across a landscape where bumblebee colonies are intensively used to pollinate berry crops. Colonies were placed inside strawberry greenhouse crops and in woodlands adjacent and distant to crops, in winter and in spring, as representative periods of high and low use of colonies, respectively. Worker bumblebees were collected from colonies upon arrival from a producer and 30 days after being placed in the field. The abdomen of each bumblebee was morphologically inspected for a range of internal parasites. Upon arrival, 71% of the colonies were infected by spores of Nosema. Three bumblebees from two colonies harboured Apicystis bombi spores at the end of their placement in woodlands adjacent to the crops. Nosema colony prevalence did not change significantly either among sites or between seasons. We found no evidence for the density of commercial B. terrestris impacting Nosema prevalence in those commercial colonies, but our results highlight the potential risk for parasites to be transmitted from commercial bumblebees to native pollinators. [ABSTRACT FROM AUTHOR]

The rate of living theory posits that higher metabolic rates negatively affect lifespan. This relationship would influence trade-offs among life history traits associated with energy production and allocation. These trade-offs may also apply within a species, resulting in differences among individuals in life history traits. In this study, we use the bumble bee Bombus impatiens to test for a relationship between metabolic rate and lifespan. We measured the resting metabolic rates of workers throughout their lives and noted their lifespans in the laboratory. Our results show that (1) resting metabolic rate inversely correlated with potential lifespan and (2) resting metabolic rate was not affected by age. These results suggest that within a species, individual differences in life-history trade-offs may exist as predicted by the rate of living theory. [ABSTRACT FROM AUTHOR]

Climate and land-use change are recognised as the two main drivers of the ongoing reorganisation of Earth's biodiversity, but understanding precisely their role in shaping species' distributions and communities remains challenging. In mountainous regions, we typically observe an uphill shift of species' altitudinal ranges caused by increasing temperatures, but it is difficult to predict how this process interacts with land-use change. Here, we replicated an inventory of bumblebees that took place in the 1960s in Norway. Focusing on subalpine areas, we reported changes in species richness and community temperature index (CTI), a measure of the relative proportion of warm- and cold-adapted species, at low and high altitude. Using aerial photographs and meteorological data, we tested the relationship between climate and land-cover changes and changes in species richness and CTI. We observed an overall increase in CTI consistent with a gradual species turnover driven by climate change. There was on average an increase in species richness at high altitudes, while low-altitudes communities tended to become less species-rich. Moreover, we observed a negative correlation between species richness and temperature and precipitation trends, suggesting a detrimental effect of climate change. Thanks to the replication of an historical inventory, we were able to show evidence for an effect of climate, and possibly land-cover, change on subalpine bumblebee assemblages. These results can contribute to a better understanding of the processes driving biodiversity changes in subalpine areas in a context of global climate and landscape changes. [ABSTRACT FROM AUTHOR]

The precise quantification of microRNAs (miRNAs) expression level is a critical factor in mastering its functions. We evaluate the suitability of two common genes and ten miRNAs as normalizers for miRNA quantification in the head and ovary at different reproductive status of bumblebees, Bombus lantschouensis by using four different algorithms and one consensus rank approach. For the head and ovary combination, miR-275 was the best candidate. For different tissues, miR-275 was the most stable candidate in the head, while the candidate for the ovary was miR-277. To test the best candidate accuracy, miR-315 was demonstrated to be downregulated based on miR-275 normalization in ovipositor bumblebees. The miR-275 and miR-277 combination is identified to be the most reliable and suitable reference genes for the head and ovary of bumblebees. [ABSTRACT FROM AUTHOR]

A worldwide decline of many bee species has been reported, but conversely some species seems to be in expansion. Nonetheless species truly in expansion may be overestimated, especially when they are considered as a whole, and information about intraspecific lineages is lacking. The objective of this study was to test whether the bumblebee species Bombus morio and B. pauloensis will be safe under future climate changes. Specifically, test if these bees will suffer geographic decline or expansion; test whether each phylogeographic lineage within B. pauloensis will respond differently in modeling of future geographic distribution given climate change; find stable areas holding high genetic diversity based on predicted future climatic changes; and test whether these areas are covered by existing protected areas. To reach the objectives we performed analyses using phylogeographic data already available and climate change information to model the demography of the panmictic B. morio and the phylogeographic lineages in B. pauloensis. Our results suggest that both species will suffer a reduction in suitable area and that the reduction in distribution is masked for B. pauloensis. When each clade was separately analyzed, the ones in the edge of the species distribution are the most likely to decline. We found a large future refuge in eastern state of São Paulo and state of Rio de Janeiro for B. morio and for the clades of B. pauloensis. This refuge seems to show high levels of species richness and endemism for different taxa. Thus, by protecting this area we will be preserving not only the pattern of biodiversity but also the processes that generate and maintain them for many other species. [ABSTRACT FROM AUTHOR]

Bumble bees (Bombus) play key roles as pollinators in temperate ecosystems. Some North American species have declined due to factors that include habitat loss, parasites, pesticides, and climate change. In many regions conservation is hampered by lack of quantitative data on historical abundance and distribution, making status assessments difficult. From 2012 to 2014, with help from 53 citizen scientists, we conducted surveys to determine the status of bumble bees throughout Vermont, USA. For historical comparison, we identified and digitized bumble bee specimens from 13 public and private collections. Our dataset contained 12,319 records, which we separated into historic (1915-1999; n = 1669) and modern (2000-2014; n = 10,650) periods, with our survey contributing 94% of modern data. Of 17 species, four were not detected and four showed significant declines. Rarefaction indicated that both modern and historic datasets slightly underestimated known species richness, diversity, and abundance, but confirmed a strong decline for all three parameters. Declining species broadly accorded with those reported elsewhere in eastern North America, and included those in subgenera Bombus, Fervidobombus, and Psithyrus. Four species in the subgenus Pyrobombus (B. bimaculatus, B. impatiens, B. ternarius, and B. vagans) greatly increased in relative abundance in the modern period. Landscape factors such as road density, elevation, and land use strongly predicted distribution of some species. Species diversity was correlated positively with grasslands, and negatively with deciduous and mixed forest cover, while abundance was correlated positively with evergreen forest cover, yet negatively with deciduous forest. [ABSTRACT FROM AUTHOR]

The current worldwide pollinator decline is caused by the interplay of different drivers. Several strategies have been undertaken to counteract or halt this decline, one of which is the implementation of wildflower fields. These supplementary flowers provide extra food resources and have proven their success in increasing pollinator biodiversity and abundance. Yet such landscape alterations could also alter the host-pathogen dynamics of pollinators, which could affect the populations. In this study, we investigated the influence of sown wildflower fields on the prevalence of micro-parasites and viruses in the wild bumble bee Bombus pascuorum, one of the most abundant bumble bee species in Europe and the Netherlands. We found that the effect of sown wildflower fields on micro-parasite prevalence is affected by the composition of the surrounding landscape and the size of the flower field. The prevalence of micro-parasites increases with increasing size of sown wildflower fields in landscapes with few semi-natural landscape elements. This effect was not observed in landscapes with a high amount of semi-natural landscape elements. We elaborate on two mechanisms which can support these findings: (1) "transmission hot spots" within the altered flower-networks, which could negatively impact hosts experiencing an increased exposure; (2) improved tolerance of the hosts, withstanding higher parasite populations. [ABSTRACT FROM AUTHOR]

We present novel dynamic mixture models for the monitoring of bumblebee populations on an unprecedented geographical scale, motivated by the UK citizen science scheme BeeWalk. The models allow us for the first time to estimate bumblebee phenology and within-season productivity, defined as the number of individuals in each caste per colony in the population in that year, from citizen science data. All of these parameters are estimated separately for each caste, giving a means of considerable ecological detail in examining temporal changes in the complex life cycle of a social insect in the wild. Due to the dynamic nature of the models, we are able to produce population trends for a number of UK bumblebee species using the available time-series. Via an additional simulation exercise, we show the extent to which useful information will increase if the survey continues, and expands in scale, as expected. Bumblebees are extraordinarily important components of the ecosystem, providing pollination services of vast economic impact and functioning as indicator species for changes in climate or land use. Our results demonstrate the changes in both phenology and productivity between years and provide an invaluable tool for monitoring bumblebee populations, many of which are in decline, in the UK and around the world. Supplementary materials accompanying this paper appear online. [ABSTRACT FROM AUTHOR]

Species taxonomy of bumblebees (Bombus Latreille, 1802) is well known to be problematic due to a potentially high intra-specific variability of morphological traits while different species can converge locally to the same color pattern (cryptic species). Assessing species delimitation remains challenging because it requires to arbitrarily select variable traits whose accuracy continues to be debated. Integrative taxonomic approach seems to be very useful for this group as different independent traits are assessed to propose a rational taxonomic hypothesis. Among operational criteria to assess specific status, the reproductive traits involved in the pre-mating recognition (i.e., the male cephalic labial gland secretions, CLGS) have been premium information. Since these secretions are supposed to be species-specific, these chemical traits can bring essential information where species delimitation is debated. Here, we describe and compare the CLGS of 161 male specimens of nine Alpinobombus taxa: alpinus, balteatus, helleri, hyperboreus, kirbiellus, natvigi, neoboreus, polaris, and pyrrhopygus. We aim also to test the congruence between this new information (reproductive traits) and published genetic dataset. Our results emphasized six distinct groups with diagnostic major compounds: (a) alpinus + helleri with hexadec-9-en-1-ol; (b) polaris + pyrrhopygus with two major compounds hexadec-9-en-1-ol and hexadec-9-enal; (c) balteatus with tetradecyl acetate; (d) kirbiellus with geranyl geranyl acetate; (e) hyperboreus + natvigi with octadec-11-en-1-ol; (f) neoboreus with octadec-9-en-1-ol. Based on this new information, we can confirm the species status of B. alpinus, B. balteatus, B. hyperboreus, B. kirbiellus, B. neoboreus, and B. polaris. We also confirm the synonymy of helleri (Alps) with alpinus (Sweden). However, the specific status of natvigi (Alaska) and pyrrhopygus (Sweden) is questionable and these taxa do not have specific CLGS composition. [ABSTRACT FROM AUTHOR]

The capacity to produce seed, both by selfing and outcrossing, or mixed mating strategies, is considered a mechanism for overcoming unpredictable pollinator availability. In the present study, we investigate breeding system, insect visitations and the role of insect visitors in the pollination of five species of Oenothera subsect. Oenothera. Field experiments showed that autonomous selfing occurs at bud stage, prior to the opening of the flower. Control flowers showed similar seed set to hand-pollinated flowers, whereas emasculated flowers and those subject to open pollination set fewer seed. These results are consistent with the hypothesis that the investigated Oenothera exhibit a great capacity for autonomous selfing and that selfing is selected in order to provide reproductive assurance. Although flowers were visited mostly by nocturnal lepidopterans, these insects did not precipitate pollination and are thus considered nectar thieves. Conversely, analysis of pollen loads and behavior during foraging by diurnal insect visitors revealed that honeybees and bumblebees are the probable pollinators. We conclude that production of flowers capable of autonomous selfing at bud stage, followed by anthesis and opportunities for outcrossing, probably improves the invasive potential of these Oenothera in Europe, together with a rapid increase in their populations, even when pollinators are scarce. [ABSTRACT FROM AUTHOR]