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Qualifying pollinator decline evidence--Response
Abstract
Ghazoul is accurate in pointing out that we have no population data on the majority of pollinators, that the data we do have are biased toward a small number of taxa (bumblebees, honey bees, and butterflies), and that data are far better for Europe and North America than for elsewhere. These points
... Linkages with agricultural management: Pollinator declines have been linked to multiple factors, including pesticides [153], parasites [154], climate change [155,156] and habitat loss [157], of which habitat loss is considered the most pervasive [154,158,159]. Reducing the application of pesticides in the direct vicinity of kettle holes and maintaining herbaceous buffer strips is likely to improve the suitability of kettle holes as habitats for pollinators. ...
... Linkages with agricultural management: Pollinator declines have been linked to multiple factors, including pesticides [153], parasites [154], climate change [155,156] and habitat loss [157], of which habitat loss is considered the most pervasive [154,158,159]. Reducing the application of pesticides in the direct vicinity of kettle holes and maintaining herbaceous buffer strips is likely to improve the suitability of kettle holes as habitats for pollinators. ...
Kettle holes are small water bodies of glacial origin which mostly occur in agricultural landscapes. They provide numerous ecosystem services (ES), but their supply may be negatively affected by agricultural management. We conducted a literature review to identify which ES are supplied by kettle holes and to analyze feedbacks with agricultural management. Taking Germany as a test case, we also analyzed how kettle holes are addressed in policy documents and for which ES they are regulated. This was done to identify the societal value officially associated with kettle holes. The literature review found eight ES attributed to kettle holes, of which hydrological cycle and flood control, chemical condition of freshwaters, nursery populations and habitats and biotic remediation of wastes were addressed most often. In contrast, only the provision of habitat service was addressed in German policy documents related to kettle holes. We identified types of agricultural management that negatively affected the supply of ES by kettle holes, in particular artificial drainage, high levels of pesticide and fertilizer application, and management where tillage and erosion result in elevated sediment inputs. Additionally, climate change may lead to an increased drying up of kettle holes. Based on our finding, we conclude that the intensity of agricultural management around kettle holes threatens the supply of all ES while only the service of providing habitats for biodiversity is addressed in German policy regulations. Further regulation is required to induce agricultural management change towards a conservation of all ES supplied by kettle holes.
... [1][2][3][4] This phenomenon has been particularly recorded in honey bees (Apis mellifera). [5] The global loss of honey bee colonies has detrimental consequences for plant biodiversity, bee products, and negative economic and societal effects. [6] As a result, many scientific studies have been carried out to understand the mechanisms underlying phenomena such as colony weakening or collapse and colony mortality observed in most of the countries practicing intensive agriculture. ...
... Many reports concluded that biotic and abiotic factors are suspected to be involved in this phenomenon, either alone or in combination. [2,5,[7][8][9][10] Potential causes are exposure to i) environmental and in-hive chemicals, [11,12] ii) agricultural practices, [13,14] iii) infection by micro-organisms and predation by parasites, [15][16][17] and iv) nutritional factors, [18][19][20] among others, which lead to the transition from a health status qualified as normal to a health decline that would contribute to the colony collapse. [7] The expression of this pathological state may notably be linked to a decrease in the immune capacities of the bee and/or the colony. ...
Honey bees play a critical role in the maintenance of plant biodiversity and sustainability of food webs. In the last few decades, bees have been subjected to biotic and abiotic threats causing various colony disorders. Therefore, monitoring solutions to help beekeepers to improve bee health are necessary. MALDI mass spectrometry profiling has emerged within this decade as powerful to identify in routine micro‐organisms and is currently used in real‐time clinical diagnosis. We developed MALDI BeeTyping to monitor significant hemolymph molecular changes in honey bees upon infection with a series of entomopathogenic Gram‐positive and ‐negative bacteria. A Serratia marcescens strain isolated from one naturally infected honey bee collected from the field was also considered. We individually recorded a series of hemolymph molecular mass fingerprints and built, to our knowledge, the first computational model harboring a predictive score of 97.92% and made of nine molecular signatures that discriminate and classify the honey bees’ systemic response to the bacteria. Hence, we challenged our model by classifying a training set of hemolymphs and obtained an overall recognition of 91.93%. Through this work, we aimed at introducing a novel, time and cost saving high‐throughput strategy that addresses honey bee health and on an individual scale. This article is protected by copyright. All rights reserved
... Unfortunately, bumblebees are drastically declining in Europe (Carvalheiro et al., 2013;Nieto et al., 2014), North America (Cameron et al., 2011) and Asia (Williams & Osborne, 2009), which compromises the provided ecosystem services. A variety of specific or global threats have been described such as habitat destruction, decrease of both floral resources quantity and diversity, pesticides, diseases and climate change (Inouye, 2007;Williams et al., 2008;Goulson et al., 2015;Kerr et al., 2015). The relative Correspondence: Romain Moerman, Evolutionary Biology and Ecology, Universit e Libre de Bruxelles, 50 Avenue F.D. Roosevelt, B-1050 Brussels, Belgium. ...
... The optimisation of mitigation strategies to conserve plant and pollinator diversities is one of the key challenges for ecologists in the 21st century (Mayer et al., 2011). As low diversity of wild floral resources was noted as a major cause of bee decline (Biesmeijer et al., 2006;Goulson et al., 2015), one of the main actions in many recent bee conservation strategies is promoting a high diversity of resources via agro-environmental schemes (Dicks et al., 2013) but with only low consideration for the floral resource quality (Dicks et al., 2015;Vaudo et al., 2015). Field studies have questioned this strategy by showing that pollinator diversity is not always positively influenced by the plant diversity proposed in agroenvironment schemes (Wood et al., 2015). ...
1. Bumblebees are valuable pollinators of numerous wild and cultivated plants. They can forage on variable pollen resources. As some pollen species lack particular nutrients or have global low nutritional quality, it has been suggested that bumblebees mix their pollen incomes to ensure a global balanced diet. The hypothesis that a mixed pollen diet better supports bumblebee colony development than a single pollen diet has been poorly explored.
2. We compared the impact of mono-, di- and trifloral diets on microcolony development of Bombus terrestris using three pollen resources with different nutrient contents (Cytisus scoparius, Erica sp. and Sorbus aucuparia) as well as their mixes. Nine parameters (e.g. pollen efficacy: total weight of larvae/total weight of pollen collection) were used to compare the microcolony performances. Moreover, we measured the influence of the pollen diversity and nutritional composition on relevant parameters.
3. We showed that microcolonies can potentially better develop on mixed pollen diets, but single pollen diet can also be as good as mixed pollen diet. Moreover, the sterol concentration appeared as a key factor to establish the impact of a pollen diet on the bumblebee colony development.
4. This study reveals that diverse pollen diet does not necessary equate with good colony development and supports the importance of selecting floral resources by considering their nutrient contents for bee conservation management.
... Among pollinators, bumblebees (Hymenoptera, Apidae, Bombus) are the predominant wild bee pollinators for many wildflowers and crops (Corbet et al., 1991;Osborne & Williams, 1996;Baldock et al., 2015). Their conservation has therefore received major attention in recent years (Goulson et al., 2015), even as alarming evidence about their worldwide decline has accumulated (Rasmont et al., 1993;Kosior et al., 2007;Grixti et al., 2009;Cameron et al., 2011;Carvalheiro et al., 2013;Nieto et al., 2015). This population decline involves multiple causes, but one primary factor concerns modifications of the landscape matrix (Hendrickx et al., 2007;Goulson et al., 2010;Bennett & Isaacs, 2014), including destruction, fragmentation and degradation of habitats (Rathcke & Jules, 1993;Fahrig, 2003;Harris & Johnson, 2004). ...
... These alterations of habitats through modifications of landscape use (urbanisation, agricultural practices) cause shifts or decreases in the quantity and/or quality of floral resources (i.e. pollen and nectar) available for bumblebees (Biesmeijer et al., 2006;Kleijn & Raemakers, 2008;Goulson et al., 2015). ...
Bumblebees are the predominant wild pollinators for many plant species in temperate regions. A bumblebee colony requires pollen and nectar throughout its lifetime, but degraded and fragmented habitats may have gaps in the temporal and spatial continuity of floral resources.
Heathlands are open biotopes that provide favourable habitat for bumblebees like Bombus jonellus , a declining species in Belgium. In heathlands, ericaceous species are the main plants that provide pollen and nectar for bumblebees. Although the nectar composition of ericaceous species has been previously studied, data on pollen composition remain scarce.
We examined bumblebee diets (composition of their pollen loads) in Belgian heathlands over the course of a colony lifetime to assess the fidelity of bumblebees for ericaceous species. We compared nutritional values by investigating the chemical composition (amino acids, polypeptides and sterols) of the pollen of the ericaceous and dominant non‐ericaceous species present in pollen loads. No relationship was detected between the abundance of a particular plant species in bumblebee loads and its pollen composition.
The successive flowering periods and the nutritional quality of pollen of ericaceous species offer valuable resources for bumblebees. Ericaceous species represent a large part of bumblebee diets in heathlands, especially in early spring and late summer when the diversity of other flowering species was low.
Bumblebee pollen loads also contained non‐ericaceous flowering species that grow outside heathlands. Thus, land planning must incorporate conservation strategies for the different elements of the landscape matrix, including heathlands, peatlands, meadows and margins.
... With the exception of a few wild bees and butterflies, however, population data are scare for these unmanaged invertebrate species (NRC and NAP 2007). Even so, declines in many wild pollinator species are unfortunately obvious (Goulson et al. 2015b). Nearly 3,000 bee species are native to North America and about 40 of these bees are bumble bees-important pollinators of native plants ). ...
Executive Summary In collaboration with the National Park Service, the University of Wyoming Ruckelshaus Institute of Environment and Natural Resources and the Wyoming Natural Diversity Database completed the Natural Resource Condition Assessment (NRCA) for Agate Fossil Beds National Monument (NM). The purpose of the NRCA is to provide park leaders and resource managers with information on resource conditions to support near-term planning and management, long-term strategic planning, and effective science communication to decision-makers and the public. Agate Fossil Beds NM was authorized in 1965 and established in 1997. The purposes of the park include protecting the paleontological resources on the site and providing a center for paleontological research and fossil display; protecting, curating, and exhibiting the James H. Cook Red Cloud Native American collection; protecting and revealing the intersection between culture, landscape, and science; and preserving the short-grass prairie and Niobrara riparian ecosystems. The assessment for Agate Fossil Beds NM began in 2015 with a facilitated discussion among park leadership and natural resource managers to identify high-priority natural resources and existing data with which to assess condition of those resources. Data were synthesized to evaluate each resource according to condition, trend in the condition, and confidence in the assessment. Natural resource conditions were the basis for a discussion with park leadership and natural resource managers, who then identified critical data gaps and management issues specific to Agate Fossil Beds NM. Resource experts, park staff, and network personnel reviewed this assessment. Priority natural resources were grouped into three categories: Landscape Condition Context, Supporting Environment, and Biological Integrity. The resources categorized as Landscape Condition Context included viewshed, night sky, and soundscape. At the time of this assessment, these resources were all in good condition. Supporting Environment—or physical environment—resources included air quality, surface water quality, geology, and paleontological resources. Air quality, surface water quality, and geology were of moderate concern; the condition of paleontological resources was not available due to a lack of data on poaching and vandalism of fossils. The natural resources that composed the Biological Integrity category included vegetation, birds, fish, and pollinators. Vegetation and pollinators resources were of moderate concern, fish condition had deteriorated substantially since the late 1980s and warranted significant concern. We were unable to assign a condition to birds in the absence of specific management goals. This assessment includes a general background on the NRCA process (Chapter 1), an introduction to Agate Fossil Beds NM and the natural resources included in the assessment (Chapter 2), a description of methods (Chapter 3), condition assessments for 11 natural resources (Chapter 4), and a summary of findings accompanied by management considerations (Chapter 5). Note: This report was first published in 2019, however, an error was noted in the report resulting in this revised version. The scope/nature of the revision includes: The sentence “In 2012, a request for assistance with northern pike removal and reintroduction of native fish was denied (Medley 2012)”—included on page 188 of the original report (section 4.10.1 Background and Importance)—has been removed.
... Apis mellifera populations are exposed to different biotic and abiotic stressors that affect bee survival. Pathogens and parasites are among the most important factors that affect bee mortality (Goulson et al., 2015). This phenomenon triggers negative consequences not only for the environment but also for beekeepers who suffer severe economic losses Activity of polyphenols on Paenibacillus larvae associated with their honeybee colonies. ...
Apis mellifera populations are exposed to different biotic and abiotic stressors that affect bee survival. Paenibacillus larvae , the causative agent of American foulbrood, is one of the most important bacterial pathogens that affect bee health. In some countries, the use of antibiotics is the most common method for the prevention and treatment of P. larvae infected colonies, however this application can also increase the risk of occurrence of resistant strains. An ecological alternative is the use of vegetal extracts containing bioactive compounds, such as polyphenols. The aim of this study is to check the antimicrobial activity of phenolic extracts of apple pomace, from the cider industry, against P. larvae strains by the broth micro dilution method. In addition, the toxicity of the phenolic extracts on A. mellifera was verified using the complete exposure method. All extracts contain from 715.31 to 11348.16 μg gal/g DW, determined by Folin-Ciocalteu show antimicrobial activity against P. larvae genotype ERIC I, ranging from 23 μg/mL to 150 μg/mL. Toxicity assays of apple pomace extracts on adult bees exhibited a maximum mortality of 18% after 48h. This promising alternative will be used in the future to evaluate its toxicity at a field level.
... Apis mellifera populations are exposed to different biotic and abiotic stressors that affect bee survival. Pathogens and parasites are among the most important factors that affect bee mortality (Goulson et al., 2015). This phenomenon triggers negative consequences not only for the environment but also for beekeepers who suffer severe economic losses Activity of polyphenols on Paenibacillus larvae associated with their honeybee colonies. ...
Apis mellifera populations are exposed to different biotic and abiotic stressors that affect the bee survival. Paenibacillus larvae, the causative agent of American foulbrood, is one of the most important bacterial pathogens that affect bee health. In some countries, the use of antibiotics is the most common method for prevention and treatment of P. larvae infected colonies. However, this application can increase the risk of occurrence of resistant strains. An ecological alternative is the use of vegetal extracts containing bioactive compounds, such as polyphenols. The aim of this study is to check the antimicrobial activity of phenolic extracts of apple pomace, coming from the cider industry, against P. larvae strains by the broth micro dilution method. Besides, the toxicity of the phenolic extracts on A. mellifera was verified using the complete exposure method. All extracts contain from 715.31 to 11348.16 μg gal/g DW, determined by Folin-Ciocalteu showed antimicrobial activity against P. larvae genotype ERIC I, ranging from 23µg/mL to 150 µg/mL. Toxicity assays of apple pomace extracts on adult bees exhibited a maximum mortality of 18% after 48h. This promising alternative will be used in the future to evaluate its toxicity at field level.
... Bee colony numbers decline is a worldwide concern. Notably, 37% of the 407 species for which there is information on population change are in decline in the European Union (EU) (Goulson et al., 2015). Besides this biodiversity issue, in economic terms, the role of bees as pollinators in agriculture is of paramount importance; approximately 80% of crops (and wild plant) in Europe depend directly on them (European Union, 2019). ...
The presence of pesticide residues in bees is of great interest, given the central role of bees as indicators for environmental assessment. The goal of this article is to propose a method to capture enhanced chemical information for these central environmental indicators. Most of the methods rely on the analysis of pooled samples rather than individual specimens due to practical sample preparation method considerations and limitations in sensitivity. This leads to miss information on the mapping of pesticides and actual amount of pesticide per specimen. In this article, a nanoflow liquid chromatography system coupled to high resolution mass spectrometry (using a hybrid quadrupole-Orbitrap instrument) has been applied for the development of a multiresidue pesticide method for the determination of 162 multiclass pesticides in specific part of honeybee samples (ca. abdomen, head or thorax). The reduced flow rate provided an enhancement in sensitivity and a strong reduction of matrix effects, thus only a quick and simple ultrasound assisted extraction using minute amount of sample was required. Satisfactory results were obtained for all tested analytes with concentration levels detected lower than 0.5ng g−1 in all cases, thus being acceptable for monitoring purposes. Matrix effect was negligible for 94% of compounds. Extraction recoveries ranged from 70% to 105%, being within SANTE guidelines. Finally, he applicability of the method was demonstrated, by successful application to the analysis of contaminated honeybee samples, extracting useful information from specific bee parts of single specimens, thus, enabling pseudo spatially resolved chemical information.
... Dramatic losses in honey bee (Apis mellifera) populations have been reported worldwide over the past 20 years 1-3 . Agricultural intensification (including the use of pesticides and a decrease in resources) and the spread of parasites, either alone or in combination, are often cited as potential drivers of honey bee colony decline or weakening 4 . Among parasites, the mite Varroa destructor is considered the most harmful pest in honey bee colonies 5,6 . ...
Deformed wing virus (DWV) is considered one of the most damaging pests in honey bees since the spread of its vector, Varroa destructor. In this study, we sequenced the whole genomes of two virus isolates and studied the evolutionary forces that act on DWV genomes. The isolate from a Varroa-tolerant bee colony was characterized by three recombination breakpoints between DWV and the closely related Varroa destructor virus-1 (VDV-1), whereas the variant from the colony using conventional Varroa management was similar to the originally described DWV. From the complete sequence dataset, nine independent DWV-VDV-1 recombination breakpoints were detected, and recombination hotspots were found in the 5′ untranslated region (5′ UTR) and the conserved region encoding the helicase. Partial sequencing of the 5′ UTR and helicase-encoding region in 41 virus isolates suggested that most of the French isolates were recombinants. By applying different methods based on the ratio between non-synonymous (dN) and synonymous (dS) substitution rates, we identified four positions that showed evidence of positive selection. Three of these positions were in the putative leader protein (Lp), and one was in the polymerase. These findings raise the question of the putative role of the Lp in viral evolution.
Executive Summary In collaboration with the National Park Service, the University of Wyoming Ruckelshaus Institute of Environment and Natural Resources and the Wyoming Natural Diversity Database completed the Natural Resource Condition Assessment (NRCA) for Scotts Bluff National Monument (NM). The purpose of the NRCA is to provide park leaders and resource managers with information on resource conditions to support near-term planning and management, long-term strategic planning, and effective science communication to decision-makers and the public. Scotts Bluff NM was established in 1919. The purposes of the park include protecting and preserving the Mitchell Pass portion of the Oregon Trail and the geologic features of the bluffs. The assessment for Scotts Bluff NM began in 2015 with a facilitated discussion among park leadership and natural resource managers to identify high-priority natural resources and existing data with which to assess condition of those resources. Data were synthesized to evaluate each resource according to condition, trend in the condition, and confidence in the assessment. Natural resource conditions were the basis for a discussion with park leadership and natural resource managers, who then identified critical data gaps and management issues specific to Scotts Bluff NM. Resource experts, park staff, and network personnel reviewed this assessment. Priority natural resources were grouped into three categories: Landscape Condition Context, Supporting Environment, and Biological Integrity. The resources categorized as Landscape Condition Context included viewshed, night sky, and soundscape. At the time of this assessment, viewshed condition was of moderate concern and condition of night sky and soundscape warranted significant concern. Supporting Environment—or physical environment—resources included air quality, surface water quality, geology, and paleontological resources. Air quality warranted moderate concern, and condition of surface water quality, geology, and paleontological resources warranted significant concern. The natural resources that composed the Biological Integrity category included vegetation, birds, prairie dogs, and pollinators. Vegetation, prairie dogs, and pollinators were of moderate concern; we were unable to assign a condition to birds in the absence of specific management goals. This assessment includes a general background on the NRCA process (Chapter 1), an introduction to Scotts Bluff NM and the natural resources included in the assessment (Chapter 2), a description of methods (Chapter 3), condition assessments for 11 natural resources (Chapter 4), and a summary of findings accompanied by management considerations (Chapter 5).
By facilitating plant reproduction, pollinators perform a crucial ecological function that supports the majority of the world's plant diversity, and associated organisms, and a significant fraction of global agriculture. Thus, pollinators are simultaneously vital to supporting both natural ecosystems and human food security, which is a unique position for such a diverse group of organisms. The past two decades have seen unprecedented interest in pollinators and pollination ecology, stimulated in part by concerns about the decline of pollinator abundance and diversity in some parts of the world. This review synthesizes what is currently understood about the taxonomic diversity of organisms that are known to act as pollinators; their distribution in both deep time and present space; the importance of their diversity for ecological function (including agro-ecology); changes to diversity and abundance over more recent timescales, including introduction of non-native species; and a discussion of arguments for conserving their diversity.
In cases of acute intoxication, honeybees often lay in front of their hives for several days, exposed to sunlight and weather, before a beekeeper can take a sample. Beekeepers send samples to analytical laboratories, but sometimes no residues can be detected. Temperature and sun light could influence the decrease of pesticides in bee samples and thereby residues left for analysis. Moreover, samples are usually sent via normal postal services without cooling. We investigated the temporal dynamics of whole-body residues of imidacloprid in live or dead honeybees following a single-meal dietary exposure of 41 ng/bee under various environmental conditions, such as freezing, exposure to UV light or transfer of individuals through the mail system. Immobile, “dead” looking honeybees recovered from paralysis after 48 hours. The decrease of residues in living but paralysed bees was stopped by freezing (= killing). UV light significantly reduced residues, but the mode of transport did not affect residue levels. Group feeding increased the variance of residues, which is relevant for acute oral toxicity tests. In conclusion, elapsed time after poisoning is key for detection of neonicotinoids. Freezing before mailing significantly reduced the decrease of imidacloprid residues and may increase the accuracy of laboratory analysis for pesticides.
Overall, 9.2% of bees are considered threatened in all of Europe, while at the EU 27 level, 9.1% are threatened with extinction. A further 5.2% and 5.4% of bees are considered Near Threatened in Europe and the EU 27, respectively (101 species at both levels). However, for 1,101 species (56.7%) in Europe and 1,048 species (55.6%) at the EU 27, there was not enough scientific information to evaluate their risk of extinction and thus, they were classified as Data Deficient. When more data become available, many of these might prove to be threatened as well.
Looking at the population trends of European bee species, 7.7% (150 species) of the species have declining populations, 12.6% (244 species) are more or less stable and 0.7% (13 species) are increasing. The population trends for 1,535 species (79%) remains unknown.
A high proportion of threatened bee species are endemic to either Europe (20.4%, 400 species) or the EU 27 (14.6%, 277 species), highlighting the responsibility that European countries have to protect the global populations of these species. Almost 30% of all the species threatened (Critically Endangered, Endangered, or Vulnerable) at the European level are endemic to Europe (e.g., found nowhere else in the world).
The species richness of bees increases from north to south in Europe, with the highest species richness being found in the Mediterranean climate zone. In particular, the Iberian, Italian and Balkan peninsulas are important areas of species richness. Regarding the distribution of
endemic species, southern Europe shows the highest concentration of endemism. The largest numbers of threatened species are located in south-central Europe and the pattern of distribution of Data Deficient species is primarily concentrated in the Mediterranean region.
The main threat to European bees is habitat loss as a result of agriculture intensification (e.g., changes in agricultural practices including the use of pesticides and fertilisers), urban development, increased frequency of fires and climate change.
Insect pollinators provide a crucial ecosystem service, but are under threat. Urban areas could be important for pollinators, though their value relative to other habitats is poorly known. We compared pollinator communities using quantified flower-visitation networks in 36 sites (each 1 km2) in three landscapes: urban, farmland and nature reserves. Overall, flower-visitor abundance and species richness did not differ significantly between the three landscape types. Bee abundance did not differ between landscapes, but bee species richness was higher in urban areas than farmland. Hoverfly abundance was higher in farmland and nature reserves than urban sites, but species richness did not differ significantly. While urban pollinator assemblages were more homogeneous across space than those in farmland or nature reserves, there was no significant difference in the numbers of rarer species between the three landscapes. Network-level specialization was higher in farmland than urban sites. Relative to other habitats, urban visitors foraged from a greater number of plant species (higher generality) but also visited a lower proportion of available plant species (higher specialization), both possibly driven by higher urban plant richness. Urban areas are growing, and improving their value for pollinators should be part of any national strategy to conserve and restore pollinators.
The Palaearctic B ombus ruderatus (in 1982/1983) and B ombus terrestris (1998) have both been introduced into S outh A merica ( C hile) for pollination purposes. We here report on the results of sampling campaigns in 2004, and 2010–2012 showing that both species have established and massively expanded their range.
B ombus terrestris , in particular, has spread by some 200 km year ⁻¹ and had reached the A tlantic coast in A rgentina by the end of 2011. Both species, and especially B . terrestris , are infected by protozoan parasites that seem to spread along with the imported hosts and spillover to native species.
Genetic analyses by polymorphic microsatellite loci suggest that the host population of B . terrestris is genetically diverse, as expected from a large invading founder population, and structured through isolation by distance. Genetically, the populations of the trypanosomatid parasite, C rithidia bombi , sampled in 2004 are less diverse, and distinct from the ones sampled later. Current C . bombi populations are highly heterozygous and also structured through isolation by distance correlating with the genetic distances of B . terrestris , suggesting the latter's expansion to be a main structuring factor for the parasite.
Remarkably, wherever B . terrestris spreads, the native B ombus dahlbomii disappears although the reasons remain unclear. Our ecological and genetic data suggest a major invasion event that is currently unfolding in southern S outh A merica with disastrous consequences for the native bumblebee species.
We review evidence from around the world for bumblebee declines and review management to mitigate threats. We find that there is evidence that some bumblebee species are declining in Europe, North America, and Asia. People believe that land-use changes may be having a negative effect through reductions in food plants in many parts of the world, but that other factors such as pathogens may be having a stronger effect for a few species in some regions (especially for Bombus s. str. in North America). Evidence so far is that greater susceptibility to land-use change is associated world-wide with small climatic ranges, range edges, and late-starting colony-development cycles. More evidence is needed on the roles of pollen specialization, nest sites, hibernation sites, and pesticides. It is still too early to assess the success of schemes aimed at improving forage in agricultural and conservation areas. However, schemes aimed at raising public awareness have been very successful. Until proven safe, we recommend that live bumblebees should not be moved across continents or oceans for commercial pollination.
Previous studies focused mainly on the provision of ecosystem services by species movements between semi-natural and managed habitats, whereas data on spillover effects between two managed habitats or between habitats that provide target resources in non-overlapping time periods are lacking. We studied densities of three pollinator groups on sunflower fields as a late mass-flowering crop in 16 landscapes that differed in the relative cover of oil-seed rape as an early mass-flowering crop, in the relative cover of sunflowers and in the relative cover of semi-natural habitats. Our aim was to evaluate dynamics between two crops with non-overlapping flowering periods. Densities of bumble bees in late-flowering sunflower fields were enhanced by early-flowering oil-seed rape. Highest bumble bee densities in the late-flowering crop were reached in landscapes that combined high relative covers of oil-seed rape and semi-natural habitats. Further, low relative covers of oil-seed rape in spring led to decreased bumble bee densities in late-flowering sunflower fields in landscapes with high relative covers of sunflower fields (dilution effect), whereas in landscapes with high relative covers of oil-seed rape, no dilution of bumble bees was found. Thus, our results indicate that early mass-flowering crops can mitigate pollinator dilution in crops flowering later in the season. We conclude that the management of landscape-scale patterns of early and late mass-flowering crops together with semi-natural habitats could be used to ensure crop pollination services. Similar processes could also apply for other species groups and may be an important, but so far disregarded, determinant of population densities in agroecosystems.
There is evidence that pollinators are declining as a result of local and global environmental degradation [1-4]. Because a sizable proportion of the human diet depends directly or indirectly on animal pollination [5], the issue of how decreases in pollinator stocks could affect global crop production is of paramount importance [6-8]. Using the extensive FAO data set [9], we compared 45 year series (1961-2006) in yield, and total production and cultivated area of pollinator-dependent and nondependent crops [5]. We investigated temporal trends separately for the developed and developing world because differences in agricultural intensification, and socioeconomic and environmental conditions might affect yield and pollinators [10-13]. Since 1961, crop yield (Mt/ha) has increased consistently at average annual growth rates of approximately 1.5%. Temporal trends were similar between pollinator-dependent and nondependent crops in both the developed and developing world, thus not supporting the view that pollinator shortages are affecting crop yield at the global scale. We further report, however, that agriculture has become more pollinator dependent because of a disproportionate increase in the area cultivated with pollinator-dependent crops. If the trend toward favoring cultivation of pollinator-dependent crops continues, the need for the service provided by declining pollinators will greatly increase in the near future.
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