Abstract and Figures

In Western Europe agricultural management was intensified in the period 1950–2010 with negative consequences for ecosystem services, such as pollination, especially in countries with a large proportion of agriculture. Farmland represents 66% of the Danish landscape, but little is known about wild bees despite that 75% of the country’s wild and cultivated plant species depend on insect pollination. Strawberry (Fragaria × ananassa) gains considerable benefits from insect pollination and abundance, species richness and functional diversity, are all important elements. We surveyed the diversity of wild bees during strawberry flowering by sampling bees with pan-traps along permanent margins bordering strawberry fields on six organic and six conventional farms in eastern Denmark and compared the results of the survey with that of sampling site farming practice and field margin forage availability. The majority of bees sampled were polylectic solitary ground-nesting bees known to forage on species of the rose family. This indicates that these bee species are potential pollinators of strawberries, and the low number of specialized bees suggests that the bee community was affected by the simplified landscapes. Temporal trends in abundance, species richness, and body size of the bees, suggest that the functional diversity of pollinator assemblages available differed for early- and late-flowering strawberries. Fewer plants species and a lower plant cover were found in the margins of sprayed fields. Abundance and diversity of the wild bees were neither correlated with the use of herbicides and insecticides, nor with plant species richness or flowering plant cover.
Content may be subject to copyright.
Journal of Meliology
Bee Biology, Ecology, Evolution, & Systematics The latest buzz in bee biology
No. 82, pp. 1–12 23 January 2019
Copyright © E.J. Ahrenfeldt, J. Kollmann, H.B. Madsen, H. Skov-Petersen, & L. Sigsgaard.
1, Johannes Kollmann, Henning Bang Madsen,
Hans Skov-Petersen, & Lene Sigsgaard1
  
  Fragaria × ananassa 
            -
        
           
            
   
  
Journal of MelittologyNo. 82
   
          
et alet al
et alet alet al
   
et al
gathorpe et al
          
et alet alet al.,
  
et alet alet al
          
       
 -
et al
   
et al
et al
Fragaria × ananassa
et alet
alet al
   
          
Ahrenfeldt & al.: Generalist bees dominate managed land2019
       
   
               
           
  
  
        
Apis mellifera
     
  
  
Journal of MelittologyNo. 82
Table 1.
     
Farming practice Farming intensity* Field # Locality UTM-East UTM-North Plant species Plant cover (%)
Conventional High C1 L. Skensved    
     
 Slagelse    
 Skælskør    
  
      
 Klippinge    
      
     
 Klippinge    
 Skælskør    
     
 L. Skensved    
  
     i.e.,
Ahrenfeldt & al.: Generalist bees dominate managed land2019
   
  -
  Andrena spp., Halictus
spp., and LasioglossumAndrena
      
Osmia spp. and Chelostoma
 : Sampling
of Andrena
           
     
       
   
    
    
Journal of MelittologyNo. 82
 
et alet al
Wild bees High intensity Low intensity Total bees Floral relationship
Andrena bicolor 1 1 
A. carantonica    
A. chrysosceles 1 1 
A. cineraria 1  
A. fucata 11
A. fulva 1  
A. haemorrhoa    
A. helvola    
A. minutula  
A. minutuloides  
A. nigroaenea    
A. nitida 11
A. praecox   
A. semilaevis  
A. subopaca  
A. tibialis 1 
A. wilkella  
Total Andrena spp. 136 441 577
Bombus cryptarum  
B. hortorum 1 1 
B. hypnorum 1  
B. lapidarius 1 1  
B. lucorum  
B. pascuorum 1 
B. pratorum 1  
B. terrestris  
Total Bombus spp. 11 19 30
Table 2.
       
Ahrenfeldt & al.: Generalist bees dominate managed land2019
et al-
        
     et alet al.,
 
Table 2.
Wild bees High intensity Low intensity Total bees Floral relationship
Halictus tumulorum  
Lasioglossum albipes  
L. calceatum  
L. leucopus  
L. minutissimum 1 1 
L. parvulum 11
L. punctatissimum 1 1 
L. quadrinotatum 1 1 
Total Lasioglossum &
Halictus spp.
11 17 28
Nomada fabriciana  
N. ferruginata 1 1
N. avoguata  
N. marshamella  
N. panzeri   
Total Nomada spp. 8 52 60
Osmia bicornis  
Chelostoma orisomnis 1 1 
Total Osmia spp. &
Chelostoma spp.
0 6 6
Total bees 166 535 701
Total species 22 36 40
Journal of MelittologyNo. 82
     
  
    
     : Plant
         
density of Andrena-
      
      
   
        
   
Figure 1.
from the genera: Halictus Latreille, LasioglossumOsmia
and Nomada Bombus
Ahrenfeldt & al.: Generalist bees dominate managed land2019
Figure 2.
  Andrena          Halictus
Latreille, Lasioglossum   Osmia    Nomada 
et al
              
   
   
alet alet al
           
Journal of Melittology No. 82
      
    
 
Bulletin of Entomological Research
    -
Agriculture, Ecosystems & Environment
cal Conservation
cal Entomology
Trends in Ecology & Evolution
ings of the Royal Society B: Biological Sciences
 Solitary Bees and Bumblebees in a Danish Agricultural Landscape -
    -
      
Journal of Applied Ecology
Journal of Economic Entomology
    Journal of Economic Entomology 
     Chinese Journal of Ecology
       
   
Ahrenfeldt & al.: Generalist bees dominate managed land2019 11
BombusPLoS ONE
         
Agriculture, Ecosystems & Environment
    Ecological Leers
    
Journal of Animal Ecology
Biological Conservation
Bumblebee Economicsnd
Physiological Zoology
 
Agriculture, Ecosystems & Environment
 Proceedings of the Royal Society B: Biological Sci-
Insektbestøvning af Kulturplanter-
nal of Pollination Ecology
    
Biological Conservation
Journal of Insect Conservation
Proceedings of the Royal
Society B: Biological Sciences
   
Ecological Applications
Ecological Applications
        
     Agriculture,
Ecosystems & Environment
    
Journal of the American Society for Horticultural
Journal of Melittology No. 82
            
Biodiversity and Conservation
  -
 Apidologie
Agriculture, Ecosystems & Environment
  Biological Diversity in Denmark: Status and Strat-
 
        
 
           
ties and seed set. Oecologia
            
Plant-Pollinator Interactions: From Specialization to Generalization
Journal of Experimental Biology
Cytisus scoparius
Agriculture, Ecosystems & Environment
Bombus        Journal of Applied Entomology
             
Journal of Applied Ecology
The Journal of Meliology is an international, open access journal that seeks to rapidly
disseminate the results of research conducted on bees (Apoidea: Anthophila) in their
broadest sense. Our mission is to promote the understanding and conservation of wild and
managed bees and to facilitate communication and collaboration among researchers and the
public worldwide. The Journal covers all aspects of bee research including but not limited to:
anatomy, behavioral ecology, biodiversity, biogeography, chemical ecology, comparative
morphology, conservation, cultural aspects, cytogenetics, ecology, ethnobiology, history,
identication (keys), invasion ecology, management, meliopalynology, molecular
ecology, neurobiology, occurrence data, paleontology, parasitism, phenology, phylogeny,
physiology, pollination biology, sociobiology, systematics, and taxonomy.
The Journal of Meliology was established at the University of Kansas through the
eorts of Michael S. Engel, Victor H. Gonzalez, Ismael A. Hinojosa-Díaz, and Charles D.
Michener in 2013 and each article is published as its own number, with issues appearing
online as soon as they are ready. Papers are composed using Microsoft Word® and Adobe
InDesign® in Lawrence, Kansas, USA.
A Journal of Bee Biology, Ecology, Evolution, & Systematics
ISSN 2325-4467
Journal of Meliology is registered in ZooBank (www.zoobank.org), and archived at the Univer-
sity of Kansas and in Portico (www.portico.org).
Interim Editor
Victor H. Gonzalez
University of Kansas
Victor H. Gonzalez
University of Kansas
Assistant Editors
Cory S. Sheeld
Royal Saskatchewan Museum
Founding Editor & Editor Emeritus
Michael S. Engel
University of Kansas
Claus Rasmussen
Aarhus University
... Thus, bee communities strongly depend on structurally rich landscapes that offer a variety of resources . As a result, intensively managed agricultural landscapes, which offer a poor selection of floral resources, are dominated by relatively common, generalist bees (Wood et al. 2017;Ahrenfeldt et al. 2019;Grab et al. 2019). ...
... The positive effect of extensive grassland can also be ascribed to the associated reduction of intensive arable farming (Kremen et al. 2002), as we have found that the proportion of extensively managed grassland is negatively correlated with those of arable land in the studied surroundings. In this context, an increased cover of tilled agricultural land has been shown to reduce bee richness and abundance by reducing floral resources on a landscape scale (Le Féon et al. 2010;Ahrenfeldt et al. 2019). Furthermore, pesticide seedcoating and spray drift on arable land can contaminate nearby non-target areas (Pimentel 1995;Brittain et al. 2010;Botías et al. 2016). ...
... Different disturbance regimes result in distinct plant communities that in turn shape wild bee communities (Hawkins et al. 2015;Neumüller et al. 2018). In this context it has been shown, that intensively managed agricultural landscapes are dominated by generalist ground-nesting bee species (Ahrenfeldt et al. 2019). In concordance with this assumption, generalist ground-nesting species such as certain species of bumblebees, halictid bees and andrenid bees substantially contributed to the compositional dissimilarity between the three habitat types. ...
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Context Landscape and local habitat traits moderate wild bee communities. However, whether landscape effects differ between local habitat types is largely unknown. Objectives We explored the way that wild bee communities in three distinct habitats are shaped by landscape composition and the availability of flowering plants by evaluating divergences in response patterns between habitats. Methods In a large-scale monitoring project across 20 research areas, wild bee data were collected on three habitats: near-natural grassland, established flower plantings and residual habitats (e.g. field margins). Additionally, landscape composition was mapped around the research areas. Results Our monitoring produced a dataset of 27,650 bees belonging to 324 species. Bee communities on all three habitats reacted similarly to local flower availability. Intensively managed grassland in the surrounding landscape had an overall negative effect on the studied habitats. Other landscape variables produced diverging response patterns that were particularly pronounced during early and late season. Bee communities in near-natural grassland showed a strong positive response to ruderal areas. Flower plantings and residual habitats such as field margins showed a pronounced positive response to extensively managed grassland and woodland edges. Response patterns regarding bee abundance were consistent with those found for species richness. Conclusion We advise the consideration of local habitat type and seasonality when assessing the effect of landscape context on bee communities. A reduction in the intensity of grassland management enhances bee diversity in a broad range of habitats. Moreover, wild bee communities are promoted by habitat types such as ruderal areas or woodland edges.
... In crops where small solitary bees are a key provider of pollination service delivery, such as apple and oilseed (Hutchinson et al., 2021), pan traps may be an important source of complementary data. One approach is to use bowl colours that match the colour of the target crop flower (Ahrenfeldt et al., 2019;Marini et al., 2012), but more detailed pilot studies to determine the efficacy of such an approach are required. Our results support existing evidence that the driving influence behind pan trap colour efficiency is the guild (eusocial, e.g., Bombus or non-eusocial [solitary] bees) being targeted (Campbell & Hanula, 2007;McCravy, 2018;McCravy et al., 2019). ...
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• Wild bees provide a critical ecosystem service by pollinating globally important crops. Documented bee declines, notably in agricultural landscapes, therefore threaten future food security. Yet, evaluations of methods to inventory bees are rarely carried out in different crops or focus specifically upon crop pollinating species. • We utilise standardised field datasets to elucidate differences in the capacity of transect walks, observation plots and pan traps to sample wild bee pollinator communities in four contrasting crops. Our results indicate that individual survey methods detect different components of crop pollinator communities, with guild and body size potentially important causal factors behind these differences. • Transects detected half or less of the total potential pollinator community in three of our four study crops. Whilst transects were the most efficient method for sampling bumblebees, they often missed smaller solitary species, which were most efficiently sampled by yellow pan traps. • Crop type is likely an important determinant of the most suitable survey methods to sample bee pollinator communities. Whilst transects alone are sufficient in crops pollinated predominantly by bumblebees, pan traps, and potentially observation plots, may be an important addition in some crops where smaller solitary bee species are potentially important pollinators. • Our results indicate that the most efficient methods to sample bee species in agricultural landscapes are dependent upon crop type and pollinator community composition. We use our findings to make a set of recommendations on the inventorying and monitoring of bee pollinator crop communities that can inform regional and national monitoring programmes.
... We documented an effect of the native status of plants cultivated by nurseries on the functional distributions of wild bees present in nurseries, but no effect of landscape-level factors like nursery size or surrounding natural area. While most species and individuals detected were generalist, below ground-nesting, and solitary -as seems to be common in agricultural areas (Ahrenfeldt et al., 2019) -we also detected floral specialists, above-ground cavity nesters, and eusocial species. Moreover, we detected cleptoparasitic species, which serve as indicators of functionally diverse bee assemblages (Sheffield et al., 2013). ...
1. An ongoing challenge in ecology is predicting how characteristics of communities correspond to habitat features. Examining variation in functional traits across species may reveal patterns not discernible from measures of mere abundance or richness. For beneficial insects like wild bees, functional trait-based approaches are often used to characterise communities in different agricultural habitats. 2. However, no such approach has yet been applied in horticultural plant nurseries, which represent intensively managed artificial flowering plant assemblages. Certain nurseries mostly cultivate regionally native flowering plants, allowing one to test how differences between local plant assemblages may correlate with bee functional traits. 3. We surveyed bee assemblages at native and conventional plant nurseries in southern California from spring through autumn over 2 years, while also documenting the native status of blooming plants in sampling plots. Bees were classified into different functional categories based on their diet breadth, nesting location, and social organisation. 4. At native plant nurseries, we netted proportionally more specialist bee species and fewer generalist species than at conventional nurseries. Nesting location and social organisation of bee samples did not differ between nursery types. Meanwhile, landscape-level features were not associated with any observed functional trait metrics of bee collections. Furthermore, network-level specialisation of bee-plant interactions was higher at conventional nurseries. 5. Our results suggest that a horticultural cultivation practice is quantifiably correlated with the functional distribution of resident bee assemblages. These results are important and encouraging to pollinator conservation efforts in nursery systems and other human-modified landscapes dominated by ornamental plants.
... Studies investigating the value of flower plantings have mostly focused on their beneficial effects for a few common generalist bee species (Sutter et al. 2017;Grab et al. 2019;Ahrenfeldt et al. 2019;Albrecht et al. 2020) that are abundant in agroecosystems Sutter et al. 2017). Among these species are honeybees or common bumblebee species that choose host plants in respect of quantity or nutritional requirements (Leonhardt and Blüthgen 2012). ...
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Flower plantings can increase the abundance of bees and improve pollination services in the surrounding landscape. However, uncertainty remains as to whether flower plantings play a role in wild bee conservation. The aim of this study has been to examine the contribution of the composition and management of flower plantings to the attraction of bees, particularly of endangered species. In a large-scale monitoring project, wild bee data were collected on 60 flower plantings and 120 semi-natural reference plots in 20 study sites over 2 years. In total, we recorded 60,335 bees belonging to 351 species. In flower plantings, bee species richness and abundance were intricately linked to high plant richness and constant blooming throughout the season. In the first year of this study, a complimentary blooming phenology of annual and perennial plants resulted in a more constant bloom on flower plantings. In the second year, partial mowing of flower plantings mid-season enhanced floral resources during the late season. As a result, bee richness and abundance in flower plantings increased from the first to the second year. Nevertheless, the compositional heterogeneity of bees over all 20 sites in Germany did not increase from the first to the second year. We conclude that diverse and constant blooming throughout the season is the most important factor for promoting bees in flower plantings. To ensure sufficient beta diversity over a large spatial scale, we recommend the adjustment of seed mixtures according to the geographical region.
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Arthropods are essential to maintaining healthy and productive agricultural systems. Apples are cultivated worldwide and rely on pollination. Honey bees are used for pollination but wild bees and other arthropods also contribute to pollination. Flower visitors can also be natural enemies or herbivores. In some cases, such as Syrphids, a group can have more than one role, adults being pollinators and the larvae being natural enemies of pests. In the present study, we assessed the biodiversity of arthropod flower visitors in four Danish apple orchards and compared the use of molecular and non-molecular techniques to study arthropod communities in agricultural ecosystems. Arthropod DNA collected from apple flowers was analysed by metabarcoding and pollinators were recorded through visual assessment in the orchards. These techniques resulted in two complementary lists of arthropods detected. Non-bee arthropods constituted a big part of the community of apple flower visitors by both methods. Metabarcoding detected 14 taxa and had 72% species resolution while visual census identified 7 different taxa with 14% species resolution. This study showed the importance of using different sampling methodologies to obtain a more accurate picture of fauna present. It also revealed the high presence of non-bee arthropods visiting flowers in apple orchards. The outcome of our study provides information regarding the effects of management practices on arthropod biodiversity, which can contribute to informing on suitable management practices to increase crop yield and maintain healthy agricultural systems.
Vibrating bees are the main pollinators of the tomato plant (Solanum lycopersicum L.). Knowledge of other alternative food resources for these bees is fundamental for pollinator management actions in agricultural areas. The objective of this study was to evaluate the plants used as food resources for the main pollinators Bombus morio (Swederus) and Exomalopsis analis Spinola in plantation areas. The study was conducted in 12 plantation areas in São José de Ubá, southeastern Brazil, during the flowering period of S. lycopersicum. The pollen material contained on the hind legs of 40 B. morio females and 72 E. analis females was analyzed and compared with the reference slides made from 155 flowering plant species (35 botanical families) sampled close to the plantations. The pollen material was submitted to acetolysis and mounted in glycerin gelatin and analyzed under optical microscope. From B.morio corbiculae were identified 188 pollen types (52 identified from reference slides) and 189 types from E. analis scopae (54 in reference slides). Besides tomato pollen, other most abundant types belong to Fabaceae (8%) in B. morio samples, and Hyptis and Solanum sp in E. analis samples. The trophic niche overlap was close to zero when the tomato pollen was disregarded, indicating that both pollinators use distinct sources. The results confirm the generalist character of tomato pollinators; in addition, the use of floral resources from several other plants, even at tomato flowering peak, emphasizes the importance of maintaining flowering plant composition around agricultural areas.
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A comparative study was made on the flower-visiting behavior and pollination ecology of Apis mellifera, Bombus hypocrita, and Bombus terrestris on greenhouse strawberry in Beijing. As for A. mellifera, the temperature at which the bee left nest, temperature for initial working, visiting duration on a single flower, and time interval between visiting two flowers were all significantly higher (P<0.01), compared with B. hypocrita or B. terrestris, while the latter two bee species had no significant differences in these behaviors (P>0.05). The proportion of the pollens carried to the nest by the three bee species ranked as A. mellifera > B. hypocrita > B. terrestris, and the activity of the pollens carried by the bees ranked as A. mellifera > B. hypocrita = B. terrestris. The initial working time of B. hypocrita and B. terrestris was earlier than that of A. mellifera, and the working time within a day was longer for B. hypocrita and B. terrestris than for A. mellifera. B. terrestris had the highest working frequency within a day (P<0.01). The nutritional quality of the fruits via the pollination by the three bee species showed no significant difference (P>0.05) with the control, but after the pollination, the strawberry had a lower rate of malformed fruit and a higher single fruit weight than the control. The strawberry visited by B. hypocrita and B. terrestris had a lower rate of malformed fruit than that visited by A. mellifera (P<0.05). For the pollination of greenhouse strawberry, native bumble bee species B. hypocrita could be effectively used in place of introduced A. mellifera or B. terrestris.
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Predicting potential pollination services of wild bees in crops requires knowledge of their spatial distribution within fields. Field margins can serve as nesting and foraging habitats for wild bees and can be a source of pollinators. Regional differences in pollinator community composition may affect this spill-over of bees. We studied how regional and local differences affect the spatial distribution of wild bee species richness, activity-density and body size in crop fields. We sampled bees both from the field centre and at two different types of semi-natural field margins, grass strips and hedges, in 12 strawberry fields. The fields were distributed over four regions in Northern Europe, representing an almost 1100 km long north-south gradient. Even over this gradient, daytime temperatures during sampling did not differ significantly between regions and did therefore probably not impact bee activity. Bee species richness was higher in field margins compared with field centres independent of field size. However, there was no difference between centre and margin in body-size or activity-density. In contrast, bee activity-density increased towards the southern regions, whereas the mean body size increased towards the north. In conclusion, our study revealed a general pattern across European regions of bee diversity, but not activity-density, declining towards the field interior which suggests that the benefits of functional diversity of pollinators may be difficult to achieve through spill-over effects from margins to crop. We also identified dissimilar regional patterns in bee diversity and activity-density, which should be taken into account in conservation management.
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PAPER: INTERACTION BETWEEN THE SOLITARY BEE CHELOSTOMA FLORISOMNE AND ITS NEST PARASITE SAPYGA CLAVICORNIS - EMPTY CELLS REDUCE THE IMPACT OF PARASITES 1. Nesting behaviour and interactions between the bee Chelostoma florisomne (L.) (Megachilidae) and its nest parasite Sapyga clavicornis (L.) (Sapygidae) were studied through continual observations of individuals and dissections of bee nests. Protection of bee offspring is based on (1) the bee’s discovery and removal of parasite eggs deposited prior to the construction of a cell closure, (2) minimising the time when fully provisioned cells might be parasitised successfully, and (3) the construction of empty cells in front of brood cells. 2. An empty cell was found in front of 64.4% of all brood cells and, if the outermost brood cell in a nest was excluded, in front of 74.3% of inner brood cells. A vestibule closure is most often constructed in front of the outermost brood cell. 3. Following oviposition, the bee made only five flights, which together lasted 6–13 min, to construct a cell closure. A cell closure does not prevent the nest parasite from oviposition inside the brood cell, however, and parasite eggs deposited through the cell closure are not detected and removed by the bee. Only an additional cell closure, i.e. the formation of an empty cell, may protect a brood cell when the bee is not in the nest. The nest parasite often oviposited through the additional cell closure but its offspring were then trapped in the empty cell and starved to death. 4. Only 5.4% of the inner brood cells that were protected by an empty cell were parasitised, compared with 28.9% of those without an anterior, empty cell; 27.4% of the empty cells contained dead parasite offspring (eggs and larvae). Thus, the empty cells provided significant protection and, combined with additional means of protection of brood cells, led to a low degree of parasitism. More than 77% of the wasp offspring died at an early stage due to intraspecific interference competition within brood cells and as result of the wasps’ oviposition into empty cells. MANUSCRIPT 1: ASSESSMENT OF THE FORAGING- AND NESTING CONDITIONS FOR SOLITARY BEES AND BUMBLEBEES, AND THEIR DISTRIBUTION IN A DANISH AGRICULTURAL LANDSCAPE In a survey April through November 1997, a total of 72 solitary bee species and 19 bumblebee species were recorded in the semi-natural habitats of a Danish conventional agricultural landscape. The majority of the solitary non-inquiline bee species (59) were polylectic, but four oligoleges of Salix and six oligoleges of other plant families were recorded. The plant community of the studied area is typical of nutrient-rich soils of a conventional farmland, with annuals and vigorous species that benefit from fertilisers dominating the flora. Abundant and widespread mellitophilous plant species were all ones that may sustain a species rich but polylecticly dominated bee fauna. Abundance of solitary bees and bumblebees were correlated with mellitophilous plant coverage in south-facing areas, whereas no correlation was found for honeybees. Furthermore, abundance of honeybees was not correlated with abundance of other bees. Bee species richness could not be explained by plant species richness or coverage in a multiple regression. Habitat parameters in a generalised linear model were able to predict abundance of males and inquilines, a measure of nest abundances in the habitats. MANUSCRIPT 2: DISPERSAL OF SOLITARY BEES AND BUMBLEBEES IN A WINTER OILSEED RAPE FIELD Dispersal distributions of solitary bees and bumblebees were studied in a winter oilseed rape field. Window-traps were placed in the rape field along a line transect perpendicular to the field edge. 19 species of solitary bees were recorded and all but four species are polylectic, including Brassicaceae as host-plant family. Through non-linear regression, the decline in solitary bee individuals versus distance from field edge significantly fitted a steep two-parameter exponential decay function. Activity of solitary bees was clearly highest within 30 metres from the field edge. Apparently, solitary bees do not play any noteworthy role in the pollination of winter oilseed rape in Denmark. The traps yielded ten species of bumblebees, and a significant linear correlation was found between numbers of individuals and distance from the field edge. This result is attributed to bumblebee foraging behaviour. Bumblebees were abundant and presumably are important background pollinators of oilseed rape. Honeybees are managed pollinators of oilseed rape, and were abundant in a preceding study of the area. For unknown reasons, honeybees were caught in extremely low numbers in this study, and the most likely explanation is a decline in honeybee populations. MANUSCRIPT 3: ESTIMATING SPECIES RICHNESS AND STATUS OF SOLITARY BEES AND BUMBLEBEES IN AGRICULTURAL SEMI-NATURAL HABITATS Estimation of Western Europe number of bee species varies between 2000 and 4500 (Williams 1995) but there are substantial indications of a decline in bee species in Europe and other regions. In Denmark, wild bee species richness, distribution, and abundance have not been studied in detail for about 75 years, and nothing is known about which species are potentially vulnerable or endangered. A rough estimate of solitary bees and bumblebees includes approximately 238 species (26 genera) and 29 species respectively. In a pan-trap survey of six kilometres of semi-natural habitats in a Danish agricultural landscape, 72 solitary bee species and 19 species of bumblebees were recorded, several of which are considered vulnerable or endangered in neighbouring countries. Nesting conditions for rare cavity-nesting species and the possible role of the semi-natural habitats as corridors for species dispersal are discussed. A new group of non-parametric species richness estimators, supplied by the free-ware programme EstimateS 5 (Colwell 1997), was used to estimate true species richness in the area of study and an additional 23 potential species was depicted from abundance and distribution of the 91 recorded species. Efficiency of window-traps in yellow pan-traps for bee fauna surveys is evaluated and is found to be an efficient method for investigations of species richness and relative abundance of bees.
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Pollination improves the yield of most crop species and contributes to one-third of global crop production, but comprehensive benefits including crop quality are still unknown. Hence, pollination is underestimated by international policies, which is particularly alarming in times of agricultural intensification and diminishing pollination services. In this study, exclusion experiments with strawberries showed bee pollination to improve fruit quality, quantity and market value compared with wind and self-pollination. Bee-pollinated fruits were heavier, had less malformations and reached higher commercial grades. They had increased redness and reduced sugar-acid-ratios and were firmer, thus improving the commercially important shelf life. Longer shelf life reduced fruit loss by at least 11%. This is accounting for 0.32 billion US$ of the 1.44 billion US$ provided by bee pollination to the total value of 2.90 billion US$ made with strawberry selling in the European Union 2009. The fruit quality and yield effects are driven by the pollination-mediated production of hormonal growth regulators, which occur in several pollination-dependent crops. Thus, our comprehensive findings should be transferable to a wide range of crops and demonstrate bee pollination to be a hitherto underestimated but vital and economically important determinant of fruit quality.
Open plots of strawbery ( Fragaria sp.) or plots caged with colonies of honey bees ( Apis mellifera L.) produced less malformed fruit than plots screened to exclude large insects. Bees and large Diptera, mostly drone flies ( Eristalis spp.), were the most numerous visitors to the strawberry blossoms. A list of insects including 108 species representing 35 families frequenting strawberry blossoms in Utah was compiled. The most efficient pollinators were Apis mellifera , Halictus ligatus Say, and Eristalis spp.
Bumblebees ranging in mass from 65 mg (the smallest workers of the smallest species) to 830 mg (the largest queens of the largest species examined) maintained similar average thoracic temperatures () while foraging, even though the passive cooling rates of these bees over this size range varied fourfold. Although the bees regulated between apparent lower and upper set points despite wide ranges of body size (and over wide ranges of ambient temperature), they allowed to fluctuate between the set points. The foraging activity of queens was relatively independent of ambient temperature (), but workers (and particularly the smallest workers) were often excluded at low . Although the size-related rates of passive cooling of drones was similar to that of workers, they did not maintain the same as workers on some kinds of flowers.
The effects of farming system on plant density and flowering of dicotyledonous herb's of high value for bees were investigated in 14 organic and 14 conventional winter wheat fields and adjacent road verges. The organic and conventional winter wheat fields/road verges were paired based on the percentage of semi-natural habitats in the surrounding landscape at 1-km scale. Mean density of high value bee plants per Raunkiaer circle was significantly higher in organic winter wheat fields and their adjacent road verges than in their conventionally farmed counterparts. The effect of organic farming was even more pronounced on the flowering stage of high value bee plants, with 10-fold higher mean density of flowering plants in organic fields than in conventional fields and 1.9-fold higher in road verges bordering organic fields than in those bordering conventional fields. In summary, organic farming had a strong positive effect in both road verges and wheat fields on the density of high value bee plants. This was due to the absence of herbicides and to practices inherent to organic farming systems, such as the use of clover (a high value bee plant) as a green manure and fodder crop.