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Evidence for competition between honeybees and bumblebees; effects on bumblebee worker size
Abstract
Numerous studies suggest that honeybees may compete with native pollinators where introduced as non-native insects. Here we
examine evidence for competition between honeybees and four bumblebee species in Scotland, a region that may be within the
natural range of honeybees, but where domestication greatly increases the honeybee population. We examined mean thorax widths
(a reliable measure of body size) of workers of Bombus pascuorum, B.lucorum, B.lapidarius and B.terrestris at sites with and without honeybees. Workers of all four species were significantly smaller in areas with honeybees. We suggest
that reduced worker size is likely to have implications for bumblebee colony success. These results imply that, for conservation
purposes, some restrictions should be considered with regard to placing honeybee hives in or near areas where populations
of rare bumblebee species persist.
... High density of honeybees may result in decreased abundance of large wild bee species (Torné-Noguera et al. 2016;Henry and Rodet 2018), and a shift towards individuals of smaller body size of some bumblebee (Bombus) species (Goulson and Sparrow 2009;Elbgami et al. 2014). A possible explanation of this effect is that larger bees need more pollen and nectar than smaller ones, which becomes difficult when they are close to honeybee hives, and larger bees are drawn away from this area (Goulson and Sparrow 2009;Torné-Noguera et al. 2016;Henry and Rodet 2018). ...
... High density of honeybees may result in decreased abundance of large wild bee species (Torné-Noguera et al. 2016;Henry and Rodet 2018), and a shift towards individuals of smaller body size of some bumblebee (Bombus) species (Goulson and Sparrow 2009;Elbgami et al. 2014). A possible explanation of this effect is that larger bees need more pollen and nectar than smaller ones, which becomes difficult when they are close to honeybee hives, and larger bees are drawn away from this area (Goulson and Sparrow 2009;Torné-Noguera et al. 2016;Henry and Rodet 2018). Furthermore, larger bees can fly longer distances and forage far from hives, in sites where the competitive pressure for resources is lower (Greenleaf et al. 2007;Guédot et al. 2009). ...
... For example, long-term studies indicate that wild bee foraging behavior may change in the presence of honeybee hives, including switching the floral resource spectrum and the foraging times (Roubik 2009;Roubik and Villanueva-Gutiérrez 2009). In addition, the presence of managed honeybees may influence the fitness of wild bees, especially in colonial species such as bumblebees (Bombus; Goulson and Sparrow 2009;Elbgami et al. 2014). These and other dimensions of the potential impact of managed honeybees should also be included in future studies in our study area for a more complete understanding of the impact of beekeeping in this protected area. ...
Honeybee hives may influence pollen and nectar availability in natural ecosystems, which may consequently affect wild pollinators. We studied the effects of managed honeybee hives on wild bee diversity in Villavicencio Nature Reserve (Mendoza, Argentina). We placed pan traps at increasing distances from honeybee hives to estimate wild bee abundance, richness, and composition. Wild bee abundance did not change detectably with distance to honeybee hives, although the abundance of the most common species, Arhysosage bifasciata, increased with increasing distance to the hives. Wild bee richness increased weakly with increasing distance to hives. Although wild bee composition did not change significantly with distance to the apiaries for the full data set, it changed significantly when we excluded A. bifasciata from the analyses. We found no relationship between body size and distance to the apiaries. Overall, our results indicate that managed honeybee hives had mixed effects on the wild bee assemblage in our study area. Given the relatively low hive density used in our study compared to other studies, we recommend an adaptive management strategy with continuous impact assessment.
... honeybees, Balfour et al. 2015a, b;bumblebees, Sáez et al. 2017). Apis-Bombus resource competition has also been shown to cause fitness costs (reduced growth and reproduction) in bumblebees (Thomson 2004;Goulson and Sparrow 2009;Elbgami et al. 2014) though not honeybees in the existing literature (reviewed in Wojcik et al. 2018). ...
... Both Apis and Bombus often occur in large numbers on flowers relative to other bees and insects (Garbuzov and Ratnieks 2014b) due in part to their large eusocial colonies (Seeley 1995;Goulson 2003). The absolute and relative abundance of Apis and Bombus changes over the foraging season in the UK. ...
... Therefore, seasonal changes in both competitor abundance and resource availability could cause seasonal change in the strength of Apis-Bombus exploitative competition. However, our knowledge of this is currently limited despite the increasing (see Breeze et al. 2011) importance of these bees for the pollination of crop and wildflower plant species (Corbet et al. 1991;Carreck and Williams 1998;Woodcock et al. 2013;Garratt et al. 2014), and the potential effects of Apis-Bombus floral resource competition on bee fitness (growth and reproduction; Thomson 2004;Goulson and Sparrow 2009), foraging behaviour (Walther-Hellwig et al. 2006;Nielsen et al. 2017) and pollination effectiveness (Greenleaf and Kremen 2006). ...
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.
... Increasing the number of insect species visiting the same plants by promoting niche overlap and connectance can be beneficial for network robustness (the resilience of networks following the loss of species), and hence is often a goal in pollinator restoration (e.g., Cusser & Goodell, 2013). However, higher niche overlap may lead to direct competition if resources (i.e., nectar and pollen) are limited in space and time (Goulson & Sparrow, 2009;Wignall et al., 2020) and to indirect competition by providing opportunities for the transmission of pathogens (Proesmans et al., 2021). ...
... Applied ecology, Behavioural ecology, Conservation ecology, Entomology, Evolutionary ecology, Restoration ecology, Trophic interactions bees (Figueroa et al., 2020), and bees' niche overlap, a measure of resource sharing and a proxy for competition between taxa (Taggar et al., 2021). We focused our study on honeybees and bumblebees, two common and important crop pollinator taxa with a strong potential for competitive interactions (Goulson & Sparrow, 2009;Wignall et al., 2020) and disease transmission (Fürst et al., 2014;Manley et al., 2019;Piot et al., 2022). ...
Abstract Ecological restoration programs are established to reverse land degradation, mitigate biodiversity loss, and reinstate ecosystem services. Following recent agricultural intensification that led to a decrease in flower diversity and density in rural areas and subsequently to the decline of many insects, conservation measures targeted at pollinators have been established, including sown wildflower strips (WFS) along field margins. Historically successful in establishing a high density of generalist bees and increasing pollinator diversity, the impact of enhanced flower provision on wider ecological interactions and the structure of pollinator networks has been rarely investigated. Here, we tested the effects of increasing flower species richness and flower density in agricultural landscapes on bee‐plant interaction networks. We measured plant species richness and flower density and surveyed honeybee and bumblebee visits on flowers across a range of field margins on 10 UK farms that applied different pollinator conservation measures. We found that both flower species richness and flower density significantly increased bee abundance, in early and late summer, respectively. At the network level, we found that higher flower species richness did not significantly alter bee species' generality indices, but significantly reduced network connectance and marginally reduced niche overlap across honeybees and bumblebee species, a proxy for insect competition. While higher connectance and niche overlap is believed to strengthen network robustness and often is the aim for the restoration of pollinator networks, we argue that carefully designed WFS may benefit bees by partitioning their foraging niche, limiting competition for resources and the potential for disease transmission via shared floral use. We also discuss the need to extend WFS and their positive effects into spring when wild bee populations are established.
... Bumblebees, in turn, preferred meadow mixtures enriched with selenium and did not react positively to zinc (Figure 7). This phenomenon can be supported by the fact that bumblebees and A. mellifera share the same or similar food sources, which can lead to competitive behavior between them [55]. In the case of high A. mellifera density at a locality, bumblebees are outcompeted by A. mellifera for other food sources [56]. ...
... We explain their connection to untreated meadow mixtures by reference to competitive pressure caused by the high density of social pollinators on the treated meadow mixtures. High abundance of social bee species can have a negative effect on foraging behavior, reproduction, and even whole populations of sensitive pollinator taxa [55,66,67]. The continuously high density and activity of social pollinators thus leads to competition with other species, and non-social species may gradually be displaced [68,69]. ...
Low plant species richness and abundance, as well as contamination, can lead to a lack of nutrients in the diets of pollinators. This can cause increased oxidative stress, low resistance to disease and reduced detoxification ability. We proposed three forage mixtures with different botanical compositions, all of which should provide continuous forage for a wide range of pollinators. The monitored mixtures were treated by foliar application with selenium and zinc. Both elements should increase the quality of pollen and nectar. The effect of meadow mixtures and microelements on pollinator abundance, richness, and preference was evaluated using data obtained via the line transect method. Furthermore, the amount of selenium and zinc in the flowers was determined. It was found that the microelement treatment did not have any effect on the abundance and richness of the main pollinator taxa, which were affected only by a botanical composition of meadow mixtures. However, a preference for zinc-treated forage was observed in Apis mellifera, and a preference for selenium-treated forage was observed in Bombus spp. These two eusocial taxa appear to respond to an increased amount of microelements in the treated meadow mixtures. On the contrary , Lepidoptera was tied to untreated forage, where they were probably pushed by social bee species due to the competition.
... Another negative impact on wild bee species is that managed bees can be transported into new environments and compete for floral resources (Cane & Tepedino, 2017;Goulson & Sparrow, 2009;Henry & Rodet, 2018;Hung et al., 2019;Torné-Noguera et al., 2016) not just with wild bees but also other pollinating insects (Lindström et al., 2016). Some wild bee species travel only short distances to feed (Gathmann & Tscharntke, 2002), whereas the European honey bee can travel many kilometers to forage for food, encroaching on already occupied foraging areas of wild bees. ...
... Secondly, for some native bee advocates, there is a tension in the conversation about native bees and honey bees, so much so that it seems more appropriate to say native bees versus honey bees (Alaux, Le Conte & Decourtye, 2019;Colla & Nalepa, 2019;Durant, 2019;Goulson & Sparrow, 2009). There is also an existing tension between bee keepers themselves where distinctions are made between small scale and industrialized commercial bee keeping (Lorenz, 2016). ...
One million species are threatened with extinction globally, including more than half of the native bee species in North America. In Canada, as of July 2020, 42 municipalities have signed a resolution to commit to the standards of the Bee City Canada program which includes creating and enhancing pollinator habitat, along with celebrating and raising awareness about pollinators in their communities. Our central argument is that the commodification of pollination has detrimental effects on people, pollinators, and ecosystems, and that a diverse economies framework is one conceptual model that can help shift our perspective. Within the 'save the bees' narrative, a capitalocentric, unidimensional image of pollination persists, driven by particular forms of market power and domination. Well-intentioned individuals and groups may be constrained by industry-dominated messaging that limits their understanding of appropriate interventions. Meanwhile, Bee City Canada offers municipalities the opportunity to engage in conservation efforts by starting where they are and building on a network of Bee Cities across the country. We conducted a collective case study involving in-depth interviews with members of Ontario Bee Cities. Our thematic interpretive analysis shows how a diverse economies framework can help us to understand the value and contributions of this initiative in previously undervalued and under-recognized ways and how they help to advance a whole-of-community approach. It is only through decentering the hegemonic market-based view of pollination that true conservation of bee diversity, and associated pollination services, can be prioritized. Our findings show that Bee Cities can animate a vibrant political ecology through a collective municipal identity, by centering bees (and other pollinators by proxy).
... Steffan-Dewenter & Tscharntke (2000) anbefaler således også, at undersøgelser af konkurrenceforhold inkluderer øvrige vaesentlige populationsregulerende forhold for at kunne afgøre, hvilke faktorer, der er vigtigst i forhold til populationsdynamikken hos vilde bier. For eksempel påviste Goulson & Sparrow (2009), at størrelsen (thoraxbredden) af arbejderbier hos fire humlebiarter var signifikant reduceret i landskaber med fødemangel, og hvor der også var honningbier tilstede. Undersøgelsen inkulderede imidlertid parametre som antal blomsterbesøg eller ressourceindsamling, og det var således ikke muligt direkte at relatere den reducerede størrelse til udsaetningen af honningbier. ...
... Et andet nyt studie(Valido et al. 2019) har desuden ved hjaelp af netvaerksanalyser påvist, at bestøversamfundet aendres dramatisk, når høje taetheder af honningbier udsaettes (14 stader/km 2 ), og at ikke udelukkende fødespecialister, de oligolektiske bier, men også polylektiske arter, som fx humlebier, påvirkes. Dette er i øvrigt i overensstemmelse med, hvadGoulson & Sparrow (2009), Torné-Noguera et al. (2016 og Henry & Rodet (2018) fandt. Også hvor der er masseblomstrende arter tilstede, søger honningbien føde på flere plantearter (fxValido et al. 2019, Dupont & Olesen 2009), og konkurrencen kan potentielt påvirke alle arter, der har fødeoverlap med honningbier. ...
Vilde bestøvende insekter er generelt truede. De vilde bier, dagsommerfugle og
svirrefluer, som denne rapport har fokus på, stiller imidlertid forskellige krav til
levestedet gennem forskellige dele af livscyklus. I rapporten er levestedskravene eller
habitatressourcerne, som de også kaldes, grundigt beskrevet for humlebier, enlige
bier, dagsommerfugle og svirrefluer. For at modvirke tilbagegangen af insekterne kan
iværksættes forskellige virkemidler. Rapporten gennemgår relevante eksisterende og
mulige fremtidige virkemidler i forhold til at tilgodese insekternes levestedskrav og
giver desuden anbefalinger til, hvordan det enkelte virkemiddel kan ændres for i
større grad at understøtte vilde bestøvende insekter. I modsætning til tidligere
vurderinger af virkemidler i forhold til vilde bestøvende insekter vurderer denne
rapport ikke blot, i hvilket omfang virkemidlet bidrager med egnede fødeemner, men
også hvorvidt øvrige levestedskrav er opfyldt.
... However, changes in bumble bee foraging behavior in response to the presence of honey bees have been noted in field experiments through temporal displacement, although the strength of the response can vary between bumble bee species, based on resource preferences and foraging range (Walther-Hellwig et al. 2006). There is also evidence that honey bee presence contributes to the development of smaller average sizes of worker bumble bees in colonies foraging in the same area (Goulson and Sparrow 2009). The size of worker bumble bees corresponds to their energetic efficiency and foraging ability with consequences on the potential fitness of the colony (Heinrich 1976;Spaethe and Weidenmüller 2002;Dornhaus and Couvillon 2010). ...
... Honey bees and bumble bees are both generalist pollinators that have the potential to compete for floral resources (Thomson 2004;Thomson 2006;Rogers et al. 2013;Goulson and Sparrow 2009). Here we show that bumble bee foraging was not affected by the presence of honey bees in a nectar-rich environment, but their foraging effort was more reflective of the quality and quantity of available resources. ...
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.
... Recent studies have shown that the introduction of large numbers of managed colonies into protected areas can have detrimental effects on wild bee populations [7][8][9][10][11][12][13]. There is evidence for competition between introduced managed honey bees and native wild bee pollinators in the context of floral resource limitation [14][15][16][17]. Pathogen spillover from managed to wild bee pollinators reduces pollinator health [18,19]. ...
... Current evidence for the impact of introduced managed honey bee colonies on wild bee populations [7][8][9][10][11][12][13][14][15][16][17][18][19][20] is limited and restricted to Apis-non-Apis interactions. However, introduced managed honey bees can also have a critical impact on wild populations of native honey bees [50]. ...
Recent studies have emphasized the role of the western honey bee, Apis mellifera, as a managed agricultural species worldwide, but also as a potential threat to endangered wild pollinators. This has resulted in the suggestion that honey bees should be regulated in natural areas to conserve wild pollinators. We argue that this perspective fails to appreciate the multifaceted nature of honey bees as native or introduced species with either managed or wild colonies. Wild populations of A. mellifera are currently imperiled, and natural areas are critical for the conservation of local subspecies and genotypes. We propose that a differentiation between managed and wild populations is required and encourage integrated conservation planning for all endangered wild bees, including A. mellifera.
... Apis mellifera L. (Hymenoptera: Apidae) managed colonies are increasingly being used to improve crop pollination (Degrandi-Hoffman et al. 2019;Herrera 2020). Because of pest and disease threats and risks to wild pollinator conservation, the use of managed honeybee colonies for supplemental crop pollination is increasingly being questioned (Goulson and Sparrow 2009;Potts et al. 2010a;2010b;Rader et al. 2015;Pirk et al. 2016;Vanbergen et al. 2018). As such it is important to study a wide range of native wild pollinators in order to meet the growing demand for crop pollination (Greenleaf and Kremen 2006;Garibaldi et al. 2013;Grass et al. 2018). ...
Wildflower strips are increasingly promoted in pollinator conservation schemes to maintain the stability of ecosystem services and increase crop yield. Yet, the increased area of avocado Persea americana Mill. cultivation in sub-Saharan Africa is not accompanied by measures of biodiversity conservation or the promotion of ecosystem services. We investigated the effects of flower strips on flower visitors and avocado fruit set in Kenya. A strip mixture of sunflower Helianthus annuus L., coriander Coriandrum sativum L., and alfalfa Medicago sativa L. was established at the border of four avocado plots, while four other plots with an unmanaged border served as control. The abundance of insect flower visitors and fruit set at 10 m, 55 m, and 100 m from the border of each plot were assessed during the early, peak, and late avocado flowering periods. The honeybee Apis mellifera L. and hoverflies Syrphidae spp. accounted for 22% and 71% of flower visitors, respectively. We found interactions between the treatment, distance to the border, and the avocado flowering intensity on the abundance of honeybees but not on hoverflies. Irrespective of the distance to the border and the avocado’s flowering intensity, flower strips acted as a sink for honeybees and hoverflies. Overall, the flower strip mixture of sunflower, coriander, and alfalfa did not increase pollinator abundance and avocado productivity, and it may be necessary to identify plant species for optimal benefits and study the long-term effects of floral strips on pollinators and crop production.
... Given the previously stated ecological and financial importance of bees and other pollinators, the relative merits of urban and agricultural spaces as providers of a healthy diverse forage are not in balance.Considering our samples and analyses, we conclude that urban spaces currently represent a valuable, diverse pollen and nectar resource for pollinators. While a valuable member of the global pollinator community, A. mellifera are not under threat and although urban colonies such as those in the present study can be a valuable research resource, increasing density of apiaries may in fact negatively impact wild bees further(Goulson & Sparrow, 2009;Pirk et al., 2017). Non-native and neophyte species play a critical role in expanding the diet diversity beyond native species and also in increasing the foraging season, allowing the generation of large honey reserves for the colony.AUTH O R CO NTR I B UTI O N SGraeme Fox: Conceptualization (supporting); formal analysis (lead); investigation (equal); methodology (equal); project administration (supporting); writing -original draft (equal); writing -review and editing (lead). ...
Growth in the global development of cities, and increasing public interest in beekeeping, has led to increase in the numbers of urban apiaries. Towns and cities can provide an excellent diet for managed bees, with a diverse range of nectar and pollen available throughout a long flowering season, and are often more ecologically diverse than the surrounding rural environments. Accessible urban honeybee hives are a valuable research resource to gain insights into the diet and ecology of wild pollinators in urban settings. We used DNA metabarcoding of the rbcL and ITS2 gene regions to characterize the pollen community in Apis mellifera honey, inferring the floral diet, from 14 hives across an urban gradient around Greater Manchester, UK. We found that the proportion of urban land around a hive is significantly associated with an increase in the diversity of plants foraged and that invasive and non‐native plants appear to play a critical role in the sustenance of urban bees, alongside native plant species. The proportion of improved grassland, typical of suburban lawns and livestock farms, is significantly associated with decreases in the diversity of plant pollen found in honey samples. These findings are relevant to urban landscape developers motivated to encourage biodiversity and bee persistence, in line with global bio‐food security agendas. Using 2‐barcode metabarcoding, we identified the floral diet of honeybees across an urban gradient in Greater Manchester. Bees foraging in more urbanized environments had access to a greater diversity of plants than those foraging in more rural environments. Non native and naturalized species comprised an important part of the diet of urban foraging bees along side native species.
... There is some suggestion that pathogens from imported Apis mellifera and Bombus terrestris colonies from continental Europe may be able to spread to wild bees (Mallinger et al., 2017). There is growing evidence suggesting that Apis mellifera can have a negative impact on wild aculeate species, such as through direct competition for floral resources (Goulson & Sparrow, 2009). ...
An account of the changing fortunes of Kent’s species and habitats, the pressures nature has faced and the conservation efforts undertaken over the last 10 years.
... Furthermore, larger individuals have been shown to carry bigger forage loads and are more likely to forage for nectar [31,33]. With smaller individuals carrying smaller amounts of food and the amount of food provisioning during larval development being directly linked to body size, the colony success of bumble bees seems to be linked to their body size [76]. Taken together, our results support the hypothesis that smaller bees are the result of poor quality of food and are, in turn, less effective in foraging, thereby leading to decreased colony success. ...
Pollinators and other insects are currently undergoing a massive decline. Several stressors are thought to be of importance in this decline, with those having close relationships to agricultural management and practice seemingly playing key roles. In the present study, we sampled Bombus lapidarius L. workers in grasslands differing in their management intensity and management regime across three different regions along a north-south gradient in Germany. We analyzed the bees with regard to (1) their cuticular hydrocarbon profile (because of its important role in communication in social insects) and amount of scent by using gas chromatography and (2) the size of each individual by using wing distances as a proxy for body size. Our analysis revealed changes related to land-use intensity and temperature in the cuticular scent profile of bumble bees. Decreasing body size and increasing total scent amount were explained by an interaction of land-use intensity and study region, but not by land-use intensity alone. Thus, land-use intensity and temperature influence intracolonial communication and size, both of which can have strong effects on foraging. Land management and climate are therefore probably detrimental for colony maintenance and the reproductive success of bumble bees.
... Further, however, there is also evidence that honey bee colonies can also disrupt the complex relations from which local landscapes emerge. This concern can be broadly grouped into three interconnected tensions that may arise when managed honey bee colonies are introduced into wild ecosystems: (1) possible competition with native bees for nectar and pollen (forage) [105][106][107][108][109][110][111][112][113][114]; (2) increased likelihood and severity of pathogen transmission from managed honeybees to native bee communities [114][115][116][117][118][119]; and, (3) changes in composition of wild plant communities by both providing (honey bee) and deterring (native bee) pollination [68,112,120,121]. ...
In an era of mass extinction and biodiversity crisis, it is increasingly crucial to cultivate more just and inclusive multispecies futures. As mitigation and adaption efforts are formed in response to these crises, just transitions forward require intentional consideration of the hybrid entanglement of humans, human societies, and wider landscapes. We thus apply a critical hybridity framework to examine the entanglement of the pollinator crisis with the cultural and agricultural practice of hobbyist beekeeping. We draw on ethnographic engagements with Massachusetts beekeepers and find apiculture to be widely understood as a form of environmentalism-including as both a mitigation to and adaptation for the pollinator crisis. Illustrating how power-laden socioecological negotiations shape and reshape regional environments, we then discuss how this narrative relies on the capitalistic and instrumental logics characteristic of Capitalocene environmentalisms. These rationalities, which obscure the hybridity of landscapes, consequently increase the likelihood of problematic unintended consequences. Also present, however, is a deeper engagement with hybrid perspectives, with some beekeepers even offering pathways toward inclusive solutions. We conclude that if more just and biodiverse futures are to be realized, beekeeping communities must foster increasingly hybrid visions of apiculture as situated within socioecological and contested landscapes.
... First, competition for resources within a year has the potential to restrict the ability of wild bees to produce healthy offspring (Goulson and Sparrow, 2009), however, to observe changes in the wild bee community would require measurements taken over multiple years because many offspring do not emerge until the following season. For example, two studies focused on honey bee competition with wild bees in Australia, one over a short term period (6 month; , and another over a long term study period (>2 years chronic exposure; , observed that short term competition did not alter the reproductive success of a single bee species while the long term exposure resulted in reduced fecundity of a separate bee species. ...
Large scale agricultural production can lead to a reduction in availability of habitat used by wild bees for nesting and forage and has been implicated in worldwide bee population declines. There is growing concern that further declines in wild bee populations will occur because of continued transformations of natural or seminatural landscapes into crop monocultures. Managed honey bees, often used for pollination services in agricultural systems, can compete with wild bees and are hypothesized to negatively affect their communities. Although the response of wild bees to both agriculture and honey bees (i.e., apiculture) has been studied, the relative importance of each and their potential interactions on wild bee communities are not well understood. To forecast the extent to which landscape simplification can affect wild bees and to better understand whether honey bee presence in an already disturbed landscape might further exacerbate declines, we conducted a replicated, longitudinal assessment of wild bee community richness and richness of functional guilds (e.g., floral specificity and nesting preference) in an intensively farmed region of the United States where much of the landscape is devoted to monoculture annual crop (maize and soybean) production and managed honey bee colonies co-occur. The presence of a small apiary (4 colonies) had no immediate effect on wild bee richness, suggesting honey beekeeping may not always negatively impact wild bees. Rather, landscape composition analysis showed strong responses of wild bees to land use, with communities being less speciose in landscapes with high proportions of crop production. The availability of woodland and grassland habitat, especially at the local scale (<800 m), was associated with the greatest increase in bee richness especially for rarer aboveground nesting and floral specialist species. These data suggest large scale monocultures have a greater impact on bee communities than the presence of small apiaries. The results of this research provide important information on possible solutions in agroecosystem management to support increased bee diversity where annual crop production and apiculture are practiced. Namely, mitigation of wild bee declines in such agroecosystems may benefit more from the re-integration of landscape biodiversity, with priority on the re-introduction of perennial vegetation, like that found in woodland and grassland habitats, than the restriction of honey bee apiculture.
Data Availability
Data will be archived through Iowa State Universities digital data repository.
... Uit onderzoek blijkt dat de aanwezigheid van beheerde bijenpopulaties, zoals honingbijen, een negatief effect kan hebben op wilde bijen (56)(57)(58)(59)(60). Het is daarom verstandig om hiermee rekening te houden bij de plaatsing van bijenvolken in een bepaald gebied. ...
Ecological report + communication plan towards citizens to increase the diversity and numbers of wild bee populations in the town Zeist.
... Honeybees can negatively affect the reproduction of bumblebees (Thomson, 2004) and solitary bees (Hudewenz and Klein, 2015) and can change the collection habits of bumblebees by displacing them from the area (Walther-Hellwig et al., 2006). In addition, bumblebee workers develop to a smaller size, probably due to malnutrition during the larval stage (Goulson and Sparrow, 2009). Due to these competitive effects, a total ban on beekeeping on nature reserves is more and more pronounced González-Varo and Geldmann, 2018;Kleijn et al., 2018;Saunders et al., 2018). ...
During the study, honey bee effects on wild bees were tested and hypothesized that smaller distances from beehives will increase competitions between honey bees and wild bees, while greater distances will have a deleterious effect on competition. The impact to species richness and diversity were tested with distances from beehives, considering that this may differ when large and small wild bee species are considered separately. Altogether 158 species and 13164 individuals were collected, from which 72% (9542 individuals) were A. mellifera. High variation in abundances were detected from one year to another, the species turnover by sites were 67% in site A, 66% in site V and 63% in site F. This last one was the site with previous contact with honey bees. Considering distances from beehives, significant decreases in small bee species diversity were detected from one year to another at each distances except site F, 250 m from hives. Change in species diversity and community structure of small bee species are detected from one year to another.
... Size of images in panels B through F are proportional to panel A based on measurements reported above. Insect silhouettes represent size differences relative to B. terrestris with thorax width of 5.5 mm (DeGrandi-Hoffman et al. 2004;Goulson & Sparrow 2009;Streinzer et al. 2016). predicted by the flower syndrome hypothesis (Faegri & Pijil 1966), and that flower colour distribution is consistent with a generalization principle (Waser et al. 1996;Ollerton et al. 2009). ...
• Bees are major pollinators of angiosperms and have phylogenetically conserved colour vision but differ in how various key species use achromatic information that is vital for both flower detection and size processing.
• We modelled green contrast and colour contrast signals from flowers of different countries where there are well established differences in availability of model bee species along altitudinal gradients. We tested for consistency in visual signals as expected from generalization in pollination principles using phylogenetically informed linear models.
• Patterns of chromatic contrast, achromatic green contrast and flower size differed among the three floras we examined. In Nepal there is a significant positive correlation between flower size and colour contrast in the subalpine region, but a negative correlation at the lower altitudes. At high elevations in Norway, where pollinators other than bees are common, flower size was positively correlated with colour contrast. At low and medium altitudes in Norway and in Australia, we did not observe a significant relationship between size and colour contrast.
• We thus find that the relationship between size, green and colour contrast cannot be generalized across communities, thus suggesting that flower visual signal adaptations to local pollinators are not limited to chromatic contrast.
... Managed honey bees reduce pollen and nectar availability (Dupont et al. 2004, Torné-Noguera et al. 2016, Cane and Tepedino 2017, competitively displace wild pollinators from floral resources (Dupont et al. 2004, Shavit et al. 2009, Artz et al. 2011, Lindström et al. 2016, Ropars et al. 2019) and influence their foraging behaviour (Thomson 2004, Walther-Hellwig et al. 2006, Artz et al. 2011. Ultimately, the presence of honey bees can reduce the size, biomass and/or reproduction of wild bees (Thomson 2004, Goulson and Sparrow 2009, Elbgami et al. 2014, Torné-Noguera et al. 2016. Competition may be particularly strong when resources are limited (Martins 2004, Thomson 2006, under unfavourable climatic conditions (Thomson 2016) or in homogeneous landscapes (Herbertsson et al. 2016). ...
Maintaining the diversity of wild bees is a priority for preserving ecosystem function and promoting stability and productivity of agroecosystems. However, wild bee communities face many threats and beekeeping could be one of them, because honey bees may have a strong potential to outcompete wild pollinators when placed at high densities. Yet, we still know little about how beekeeping intensity affects wild bee diversity and their pollinator interactions. Here, we explore how honey bee density relates to wild bee diversity and the structure of their pollination networks in 41 sites on 13 Cycladic Islands (Greece) with similar landscapes but differing in beekeeping intensity. Our large‐scale study shows that increasing honey bee visitation rate had a negative effect on wild bee species richness and abundance, although the latter effect was relatively weak compared to the effect of other landscape variables. Competition for flowering resources (as indicated by a resource sharing index) increased with the abundance of honey bees, but the effect was more moderate for wild bees in family Apidae than for bees in other families, suggesting a stronger niche segregation in Apidae in response to honey bees. Honey bees also influenced the structure of wild bee pollination networks indirectly, through changes in wild bee richness. Low richness of wild bees in sites with high honey bee abundance resulted in wild bee networks with fewer links and lower linkage density. Our results warn against beekeeping intensification in these islands and similar hotspots of bee diversity, and shed light on how benefits to pollination services of introducing honey bees may be counterbalanced by detriments to wild bees and their ecosystem services.
... Recent studies have focused on the effect of honeybees on the abundance and diversity of wild bees (Torné-Noguera et al., 2016), decreased resource availability for wild bees (Torné-Noguera et al., 2016), change of foraging behaviour of wild bees (Walther-Hellwig et al., 2006) and impact on their fitness (Goulson and Sparrow, 2009;Paini and Roberts, 2005), although this point is probably the less documented (Wojcik et al., 2018). ...
La crise de la biodiversité affecte le fonctionnement de tous les écosystèmes, notamment agricoles, via une perte des services écosystémiques. Favoriser les populations d’organismes à l’origine de ces services via des stratégies de diversification végétale est un levier prometteur pour maintenir une production agricole élevée ainsi que la santé des écosystèmes, mais les résultats obtenus sont variables et peu expliqués. L’objectif de cette thèse est de comprendre comment l’augmentation de la diversité cultivée impacte la structure et le fonctionnement des communautés de pollinisateurs et d’ennemis naturels en considérant leurs interactions. Nos résultats montrent que la diversification des ressources modifie la composition des communautés, pouvant mener à des interactions négatives. Dans les réseaux trophiques puceron – parasitoïde – hyperparasitoïde, la diversification semble avoir augmenté l’hyperparasitisme et la compétition entre les parasitoïdes primaires, ce qui expliquerait un contrôle des pucerons limité. L’utilisation massive des fleurs cultivées par les abeilles domestiques semble limiter l’utilisation de cette ressource par les pollinisateurs sauvages. De plus, nous avons observé une diminution du service de régulation des pucerons par les parasitoïdes en réponse à une forte abondance de pollinisateurs, signalant pour la première fois de possibles interactions négatives entre ces deux groupes. Optimiser plusieurs services écosystémiques simultanément demande de repenser les paysages agricoles en considérant l’utilisation des ressources de chaque groupe d’organismes à différentes échelles spatio-temporelles ainsi que les interactions au sein et entre ces groupes.
... We assume, food resources in an intensive agricultural landscape often are limited, but we do not know [but see 93]. Competition effects on wild bees are therefore context dependent, and have been shown to depend on local density of honey bee hives [94][95][96][97][98]; distance from apiaries [30, 99]; resource level in the landscape [49, 56; but see Lindström et al. 100], including for honey bees the availability of mass-flowering plants for nectar regardless if crops or wild flowers. Although honey bees can forage over distances up to several kilometers, they will forage within closer proximity of their hive if resources are available [101,102]. ...
A recurrent concern in nature conservation is the potential competition for forage plants between wild bees and managed honey bees. Specifically, that the highly sophisticated system of recruitment and large perennial colonies of honey bees quickly exhaust forage resources leading to the local extirpation of wild bees. However, different species of bees show different preferences for forage plants. We here summarize known forage plants for honey bees and wild bee species at national scale in Denmark. Our focus is on floral resources shared by honey bees and wild bees, with an emphasis on both threatened wild bee species and foraging specialist species. Across all 292 known bee species from Den-mark, a total of 410 plant genera were recorded as forage plants. These included 294 plant genera visited by honey bees and 292 plant genera visited by different species of wild bees. Honey bees and wild bees share 176 plant genera in Denmark. Comparing the pairwise niche overlap for individual bee species, no significant relationship was found between their overlap and forage specialization or conservation status. Network analysis of the bee-plant interactions placed honey bees aside from most other bee species, specifically the module containing the honey bee had fewer links to any other modules, while the remaining modules were more highly interconnected. Despite the lack of predictive relationship from the pair-wise niche overlap, data for individual species could be summarized. Consequently, we have identified a set of operational parameters that, based on a high foraging overlap (>70%) and unfavorable conservation status (Vulnerable+Endangered+Critically Endangered), can guide PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.
... In the field, bees experience numerous interacting stressors (e.g. decreased floral diversity, increased pesticide exposure, and competition with honey bees 68 ), often being smaller in more simplified agricultural landscapes [69][70][71][72] . As such, we do not know if small individuals that were infected succumbed to the negative health consequence of the pathogens (and therefore were not out foraging for us to collect and screen), while larger individuals could tolerate the infections and thus bias the patterns. ...
Reports of pollinator declines have prompted efforts to understand contributing factors and protect vulnerable species. While pathogens can be widespread in bee communities, less is known about factors shaping pathogen prevalence among species. Functional traits are often used to predict susceptibility to stressors, including pathogens, in other species-rich communities. Here, we evaluated the relationship between bee functional traits (body size, phenology, nesting location, sociality, and foraging choice) and prevalence of trypanosomes, neogregarines, and the microsporidian Nosema ceranae in wild bee communities. For the most abundant bee species in our system, Bombus impatiens, we also evaluated the relationship between intra-specific size variation and pathogen prevalence. A trait-based model fit the neogregarine prevalence data better than a taxa-based model, while the taxonomic model provided a better model fit for N. ceranae prevalence, and there was no marked difference between the models for trypanosome prevalence. We found that Augochlorella aurata was more likely to harbor trypanosomes than many other bee taxa. Similarly, we found that bigger bees and those with peak activity later in the season were less likely to harbor trypanosomes, though the effect of size was largely driven by A. aurata. We found no clear intra-specific size patterns for pathogen prevalence in B. impatiens. These results indicate that functional traits are not always better than taxonomic affinity in predicting pathogen prevalence, but can help to explain prevalence depending on the pathogen in species-rich bee communities.
... Instead, it is possible that B. terrestris, which has a slightly more southerly distribution (Kerr et al., 2015;Rasmont & Iserbyt, 2010 and is associated with lower altitudes (Geue et al., 2020;Kerr et al., 2015) than the B. lucorum complex, is better adapted to climate warming in other aspects. These could be for example higher tolerance to heat stress, lower susceptibility to fungal diseases (Rasmont & Iserbyt, 2012), or that the larger body size of B. terrestris (Goulson & Sparrow, 2008) allows it to forage over larger areas (Westphal et al., 2006) making this species particularly good at compensating for local lack of flowers during periods of drought. ...
While many bumblebee species decline due to climate and land-use changes, others cope well with contemporary conditions. One example is Bombus terrestris, which is common in intensively managed agricultural landscapes. During the 20th century its subgenus, which includes the B. lucorum complex (B. lucorum, B. cryptarum and B. magnus) came to dominate Scandinavian bumblebee communities, but the specific contribution of B. terrestris remains to be understood. Using historical data on males, we assessed how the relative abundances of B. terrestris and the B. lucorum complex changed over the past 150 years in southernmost Sweden. We tested if these changes differed between simplified and mixed landscapes and whether the relative abundance of B. terrestris was related to annual mean temperatures. Because floral availability has advanced as a response to climate change, we also tested if the activity period of males (estimated as catching date) has advanced and whether the advancement differs between taxa. The relative abundance of B. terrestris increased similarly in both landscapes, from 21% to 79% over the period, and this was largely explained by increasing temperature. Male activity period has advanced similarly in the two taxa, with 41 days between 1900 and 2015. Although the dominance of B. terrestris correlates clearly with annual mean temperature, it remains to disentangle why. It also remains to understand whether the success of B. terrestris occurs at the expense of other species or simply reflects that this species copes better with contemporary conditions.
... Resource depletion by honey-and bumblebees can have negative effects between these groups (Goulson and Sparrow 2009;Thomson 2016;Sáez et al. 2017). It can also affect the many species of non-Apis/Bombus bees (e.g. ...
Eusocial bees are likely to be ecologically important competitors for floral resources, although competitive effects can be difficult to quantify in wild pollinator communities. To investigate this, we excluded honeybees (HBE treatment), bumblebees (BBE) or both (HB&BBE) from wild-growing patches of bramble, Rubus fruticosus L. agg., flowers in two eight-day field trials at separate locations, with complementary mapping of per-site local floral resource availability. Exclusions increased per-flower volume of nectar and visitation rates of non-excluded bees, compared to control patches with no bee exclusions (CON). There was a large increase in average nectar standing crop volume both at Site 1 (+ 172%) and Site 2 (+ 137%) in HB&BBE patch flowers, and no significant change in HBE or BBE, compared to CON patches. Foraging bee responses to exclusion treatments were more pronounced at Site 2, which may be due to lower local floral resource availability, since this is likely to increase the degree of exploitative competition present. Notably, at Site 2, there was a 447% increase in larger-bodied solitary (non-Apis/Bombus) bees visiting HB&BBE patches, suggesting ecological release from competition. Hoverflies showed no response to bee removals. Numbers of other non-bee insect groups were very small and also showed no clear response to exclusions. Our findings reveal patterns of competitive exclusion between pollinator groups, mediated by resource depletion by eusocial bees. Possible long-term implications of displacement from preferred flowers, particularly where alternative forage is reduced, are discussed.
Significance statement
Understanding patterns of exploitative competition and displacement is necessary for pollinator conservation, particularly for vulnerable or threatened species. In this research, experimental methods reveal underlying patterns of resource competition exerted by eusocial bees in a wild pollinator community. We show that honeybees and bumblebees competitively displace each other and particularly solitary (non-Apis/Bombus) bees from bramble, an important native nectar and pollen source. Effects were stronger where local floral resource availability was identified to be limited. Notably, following experimental exclusion of both honey- and bumblebees from flowers, visitation by solitary bees increased by up to 447%, strongly suggesting ecological release from competition. These results highlight the need for informed landscape management for pollinator wellbeing, including appropriate honeybee stocking densities and improved floral resource availability.
... If, in warmer sites, workers allocate more time and energy in thermoregulating at the expense of larval feeding (Weidenmüller, 2004), successive cohorts of foragers might become smaller. Alternatively, or in addition, temperature might be correlated with the proliferation of warmth adapted parasites (Natsopoulou, McMahon, Doublet, Bryden, & Paxton, 2015), which might affect larval growth, or with competition for food resources from the warmth tolerant honeybees, known to affect negatively body size in bumblebees (Goulson & Sparrow, 2009). ...
Urbanisation is a global phenomenon with major effects on species, the structure of community functional traits and ecological interactions. Body size is a key species trait linked to metabolism, life‐history and dispersal as well as a major determinant of ecological networks. Here, using a well‐replicated urban‐rural sampling design in Central Europe, we investigate the direction of change of body size in response to urbanisation in three common bumblebee species, Bombus lapidarius , Bombus pascuorum and Bombus terrestris , and potential knock‐on effects on pollination service provision. We found foragers of B. terrestris to be larger in cities and the body size of all species to be positively correlated with road density (albeit at different, species‐specific scales); these are expected consequences of habitat fragmentation resulting from urbanisation. High ambient temperature at sampling was associated with both a small body size and an increase in variation of body size in all three species. At the community level, the community‐weighted mean body size and its variation increased with urbanisation. Urbanisation had an indirect positive effect on pollination services through its effects not only on flower visitation rate but also on community‐weighted mean body size and its variation. We discuss the eco‐evolutionary implications of the effect of urbanisation on body size, and the relevance of these findings for the key ecosystem service of pollination.
... Hudewenz and Klein (2015) showed that foraging honeybees at field realistic densities reduced red mason bee visitation rates and reproduction. Elbgami et al. (2014) found that proximity to managed honeybee hives significantly reduced the fitness of bumblebee colonies, and Goulson and Sparrow (2009) found reduced size of workers of four bumblebee species at field sites where honeybees were present. Additionally, Henry and Rodet (2018) found that distance to the apiaries controlled honeybee visitation rates rather than the number of hives in the apiaries and, thereby, the degree of competition for floral resources with wild bees at a distance up to 1100 m from the apiary. ...
This paper suggest an area model to assess the risk of negative effects on wild bees due to food competition from honeybees. The model includes four factors: (1) the total number of foraging visits by honeybees per day; (2) the foraging range of the honeybees, typically measured as a mean or median value; (3) the area covered by floral resources in the landscape; (4) the tolerable competitive pressure posed by honeybees, i.e. the no effect intensity of foraging honeybees per flowering area below which adverse effects on wild bees due to competition will not occur. However, the need of knowing the foraging range (factor 2) is eliminated in the final model using a worst-case approach. As the honeybees from an apiary disperse into the landscape, the distance between the honeybees increases, leading to a decrease in the competitive pressure. Close to the apiary, the competition may exceed the no effect level, leading to the risk of negative effects on wild pollinators, while the competition will decrease below the no effect level further away from the apiary. The model predicts the distance from the apiary needed to keep the density of foraging honeybees below no effect level to avoid competition with wild bees. In spite of rather high spatial complexity, the final model becomes simple and defines a load factor as a ratio between the number of foraging trips and the carrying capacity of the landscape.
... The way bumblebees share the plant species they pollinate might also vary, influencing the potential for intra-and interspecific competition (Fig. 1). As a general rule, it could be expected that the most abundant bumblebee species in a community might have a higher potential to influence other bumblebees through shared plants 35,36 , especially if they are generalist species or when they share traits to efficiently exploit the same type of flowering resources 37 . In addition, a negative relationship between inter-and intraspecific competition could be expected (Fig. 1), as the effect of competitors on realized niche breadth occurs both at the interspecific 19,38 and at the intraspecific level 39 . ...
Understanding the effects of landscape fragmentation on global bumblebee declines requires going beyond estimates of abundance and richness and evaluating changes in community composition and trophic and competitive interactions. We studied the effects of forest fragmentation in a Scandinavian landscape that combines temperate forests and croplands. For that, we evaluated how forest fragmentation features (patch size, isolation and shape complexity, percentage of forest in the surroundings) as well as local flowering communities influenced bumblebee abundance, richness and community composition in 24 forest patches along a fragmentation gradient. In addition, we assessed the effect of fragmentation on bumblebee–plant network specialization (H2′), and potential inter- and intraspecific competition via shared plants. Patch isolation was associated with lower bumblebee abundance, whereas flower density was positively related to both bumblebee abundance and richness. Overall, forest fragmentation reduced the abundance of forest-specialists while increasing the abundance of open-habitat species. Patches with complex shapes and few flowers showed more generalized bumblebee–plant networks (i.e., fewer specific interactions). Patch shape complexity and the percentage of forest also modified inter- and intraspecific competitive interactions, with habitat generalists outcompeting forest specialists in fragmented areas. Understanding these mechanisms is necessary to anticipate to the impact of forest fragmentation on bumblebee decline.
... Empirical evidence suggests that colony performance also increases with worker body size [51] and that larger workers outperform smaller ones at various tasks, including foraging [52,53]. Thus, colonies comprising mainly large workers will presumably acquire more resources and produce more workers and gynes than colonies with smaller workers [33,47,[54][55][56]. Yet, larger workers are likely more costly to produce as their size seems to be directly linked to the quantity of food ingested during the larval stage [57,58]. ...
Bumble bee communities are strongly disrupted worldwide through the population decline of many species; a phenomenon that has been generally attributed to landscape modification, pesticide use, pathogens, and climate change. The mechanisms by which these causes act on bumble bee colonies are, however, likely to be complex and to involve many levels of organization spanning from the community down to the least understood individual level. Here, we assessed how the morphology, weight and foraging behavior of individual workers are affected by their surrounding landscape. We hypothesized that colonies established in landscapes showing high cover of intensive crops and low cover of flowering crops, as well as low amounts of local floral resources, would produce smaller workers, which would perform fewer foraging trips and collect pollen loads less constant in species composition. We tested these predictions with 80 colonies of commercially reared Bombus impatiens Cresson placed in 20 landscapes spanning a gradient of agricultural intensification in southern Québec, Canada. We estimated weekly rate at which workers entered and exited colonies and captured eight workers per colony over a period of 14 weeks during the spring and summer of 2016. Captured workers had their wing, thorax, head, tibia, and dry weight measured, as well as their pollen load extracted and identified to the lowest possible taxonomic level. We did not detect any effect of landscape habitat composition on worker morphology or body weight, but found that foraging activity decreased with intensive crops. Moreover, higher diversity of local floral resources led to lower pollen constancy in intensively cultivated landscapes. Finally, we found a negative correlation between the size of workers and the diversity of their pollen load. Our results provide additional evidence that conservation actions regarding pollinators in arable landscapes should be made at the landscape rather than at the farm level.
... Finally, contrary to wild bees, which are often described with small foraging flight distances (100-500 m, Greenleaf et al., 2007;Zurbuchen et al., 2010), honeybees can cover large areas for resources (mean distance: 1.5 km; range from few metres to 10 km; Steffan-Dewenter and Kuhn, 2003). Goulson and Sparrow (2009) showed that the introduction of honeybees decreased the average body size of native bumblebees, a phenomenon observed when a sudden shortage of local food resources occurs, e.g. towards the end of the season. ...
Since the rise of agriculture, human populations have domesticated plant and animal species to fulfil their needs. With modern agriculture, a limited number of these species has been massively produced over large areas at high local densities. Like invasivespecies, these Massively Introduced Managed Species (MIMS) integrate local communities and can trigger cascading effects on the structure and functioning of ecosystems. Here, we focus on plant and insect MIMS in the context of plant–pollinator systems. Several crop species such as mass flowering crops (e.g. Brassica napus ) and domesticated pollinating insects (e.g. Apis mellifera , Bombus terrestris ) have been increasingly introduced worldwide and their impact on natural communities is addressed by an increasing number of scientific studies. First, we review the impacts of major insect and plant MIMS on natural communities by identifying how they affect other species through competition (direct and apparent competition) or facilitation (attraction, spillover). Second, we show how MIMS can alter the structure of plant–pollinator networks. We specifically analysed the position of A. mellifera from 63 published plant–pollinator webs to illustrate that MIMS can occupy a central position in the networks, leading to functional consequences. Finally, we present the features of MIMS in sensitive environments ranging from oceanic islands to protected areas, as a basis to discuss the impacts of MIMS in urban context and agrosystems. Through the case study of MIMS in plant–pollinator interactions, we thus provide here a first perspective of the role of MIMS in the functioning of ecosystems.
... Nesten van een Amerikaanse hommelsoort Bombus occidentalis in de nabijheid van honingbijvolken produceerden minder broed, mannetjes en koninginnen, met de meest dramatische reductie binnen 0,75 km van bijenvolken. In Schotland waren tenslotte werksters van meerdere hommelsoorten kleiner in gebieden met honingbijvolken dan in deze zonder, indicatief voor een verminderde stuifmeelconsumptie tijdens de larvale fase (Goulson & Sparrow 2009). Negatieve effecten van competitie met Honingbijen op populaties van wilde bijen komen dus zeker voor, maar veel meer onderzoek is nodig naar de precieze omstandigheden waarin deze te verwachten zijn. ...
Honey bees and wild bees are often mentioned in one move in communication and actions for bees. However, next to obvious similarities, there are also highly relevant differences between both. In this forum paper we discuss the relation between honey bees, wild bees and nature reserves, and based on that advice on the placement of honey bee hives in Flemish nature reserves. While the European honey bee is a native species in Flanders, nowadays no wild populations are left. Beekeeping is an agricultural activity and honey bees are among the most numerous bees encountered in the typically very small Flemish nature reserves, set aside for preserving native biodiversity. Despite the need for more dedicated studies, it is clear that placing bee hives with honey bees can pose an additional pressure on wild bee populations due to competition for nectar and pollen and possibly also transfer of diseases. We suggest to apply the precautionary principle and therefore advise against placing bee hives in or near nature reserves. Given the typically very limited area of Flemish nature reserves, honey bees will still make use of the flower resources in the reserves, but this measure might in most cases prevent very high densities and therefore severe competitive effects. We also call for more open communication and mutual understanding between beekeepers and nature managers, given the obvious common interest in the maintenance of flower-rich landscapes.
... For example, in thoroughly studied North America and mid-western Europe, the number of honeybee (Apis mellifera) colonies has experienced severe declines, but the trend is apparently reversed in the less investigated areas of southern Europe, where honeybee colonies seem to have been steadily increasing over large territories in the last decades [16,18,19,21]. Honeybees have been repeatedly shown to have negative impacts on wild bee populations in both natural and anthropogenic scenarios [22][23][24][25][26][27][28]. I thus formulated the hypothesis that, if the abundance of managed honeybees has been actually increasing in the Mediterranean Basin over the last decades, then a profound biome-wide alteration in the composition of bee pollinator assemblages could be currently underway there, involving a gradual replacement of wild bees by honeybees in flowers. ...
Evidence for pollinator declines largely originates from mid-latitude regions in North America and Europe. Geographical heterogeneity in pollinator trends combined with geographical biases in pollinator studies can produce distorted extrapolations and limit understanding of pollinator responses to environmental changes. In contrast with the declines experienced in some well-investigated European and North American regions, honeybees seem to have increased recently in some areas of the Mediterranean Basin. Because honeybees can have negative impacts on wild bees, it was hypothesized that a biome-wide alteration in bee pollinator assemblages may be underway in the Mediterranean Basin involving a reduction in the relative number of wild bees. This hypothesis was tested using published quantitative data on bee pollinators of wild and cultivated plants from studies conducted between 1963 and 2017 in 13 countries from the European, African and Asian shores of the Mediterranean Sea. The density of honeybee colonies increased exponentially and wild bees were gradually replaced by honeybees in flowers of wild and cultivated plants. The proportion of wild bees at flowers was four times greater than that of honeybees at the beginning of the period, the proportions of both groups becoming roughly similar 50 years later. The Mediterranean Basin is a world biodiversity hotspot for wild bees and wild bee-pollinated plants, and the ubiquitous rise of honeybees to dominance as pollinators could in the long run undermine the diversity of plants and wild bees in the region.
... However, yeast addition has a significant effect on body mass and size of workers. Worker body size provides a readily measurable indicator of resource availability during the larval stage (Goulson and Sparrow 2009). If a colony has limited resources for offspring production, this can generate a trade-off between the number and size of the members of the colony (Cueva del Castillo et al. 2015). ...
The presence of yeasts in pollen and floral nectar is rather the norm than the exception. Due to the metabolic activities of yeasts, sugar and amino acid composition of nectar often drastically change and may negatively impact the nutritional value of nectar for pollinators and hence insect fitness. On the other hand, the presence of yeasts in floral nectar may also increase its nutritional value due to yeast´s probiotic effect and the release of yeast´s metabolites. In this study, we investigated whether the presence of defined flower‐ and insect‐associated yeasts affected individual and colony fitness of the bumble bee pollinator Bombus terrestris. Specifically, we tested whether the presence of yeasts in nectar affected bumble bee foraging behavior and nectar consumption, individual growth and colony development, larval and queen mortality, and mating success. Quantitative analyses of sugar and amino acid profiles showed that nectar yeasts significantly affected the chemical composition of nectar. However, dual‐choice experiments indicated that yeast inoculation did not significantly affect foraging behavior or consumption rates. Nest development, on the other hand, was significantly affected by the presence of yeasts, but effects largely depended on species identity, with Candida bombiphila, Metschnikowia gruessii and Rhodotorula mucilaginosa having the largest positive impact on colony growth. Interestingly, the effects at the colony level were more pronounced than at the individual level. In vitro growth tests further showed that yeasts have the potential to suppress the growth of the bumble bee gut pathogen Crithidia bombi. Overall, these results demonstrate that nectar‐inhabiting yeasts can have diverse effects on bumble bee fitness and therefore may mediate plant‐pollinator mutualisms.
... In addition, the increased competition for resources caused by the introduction of a high density of managed honeybees or commercially-produced bumblebees may also create stress for wild bees. Increased competition in foraging may have negative effects on some immune system components, impairing the resistance to parasites [63][64][65][66][67][68] . N. ceranae is an emergent honeybee parasite that is abundant at some sites but completely absent at others. ...
Microsporidia Nosema are transferred among bees via the faecal-oral route. Nosema spp. spores have been detected on flowers and transferred to hives along with the bee pollen. The aim of the present study was to determine whether Nosema microsporidia are transferred by air in an apiary, in a control area (without the presence of bee colonies), and/or in a laboratory during cage experiments with artificially infected bees. The novel way of transmission by air was investigated by the volumetric method using a Hirst-type aerobiological sampler located on the ground in the apiary, in the Botanical Garden and on the laboratory floor. Concurrently, the mean rate of Nosema infections in the foragers in the apiary was estimated with the Bürker haemocytometer method. Spore-trapping tapes were imaged by means of light microscopy, Nomarski interference contrast microscopy and scanning electron microscopy. The highest concentration of Nosema spores per 1m3 of air (4.65) was recorded in August, while the lowest concentration (2.89) was noted in July. This was confirmed by a Real-Time PCR analysis. The presence of N. apis as well as N. ceranae was detected in each of the tested tapes from the apiary. The average copy number of N. apis was estimated at 14.4 × 104 copies per 1 cm2 of the tape; whereas the number of N. ceranae was 2.24 × 104 copies per tape per 1 cm2. The results indicate that Nosema microsporidia were transferred by the wind in the apiary, but not in the Botanical Garden and laboratory by air. This was confirmed by genetic analyses. DNA from immobilised biological material was isolated and subjected to a PCR to detect the Nosema species. A fragment of the 16S rRNA gene, characteristic of Nosema apis and N. ceranae, was detected. Our research adds knowledge about the transfer of Nosema spp.
... This is particularly relevant to the interactions between managed honeybees and wild bees, as well as those of the alien and native bees. The impact of domesticated bees on native pollinators can be trivial (Roubik & Wolda, 2001;Steffan-Dewenter & Tscharntke, 2000), but others showed clear effects to native bees on their reproductive success and population size (Goulson & Sparrow, 2009). Similarly, Paini and Roberts (2005) found considerable overlap in plant resources between Australian native pollinators and alien invasive bees, which led to a decline of the local bees. ...
Studies on foraging partitioning in pollinators can provide critical information to the understanding of food‐web niche and pollination functions, thus aiding conservation. Metabarcoding based on PCR amplification and high‐throughput sequencing has seen increasing applications in characterizing pollen loads carried by pollinators. However, amplification bias across taxa could lead to unpredictable artefacts in estimation of pollen compositions. We examined the efficacy of a genome‐skimming method based on direct shotgun sequencing in quantifying mixed pollen, using mock samples (5 and 14 mocks of flower and bee pollen, respectively). The results demonstrated a high level of repeatability and accuracy in identifying pollen from mixtures of varied species ratios. All pollen species were detected in all mocks, and pollen frequencies estimated from the number of sequence reads of each species were significantly correlated with pollen count proportions (linear model, R2 =86.7%, P = 2.2e‐16). For >97% of the mixed taxa, pollen proportion could be quantified by sequencing to the correct order of magnitude, even for species which constituted only 0.2% of the total pollen. In addition, DNA extracted from pollen grains equivalent to those collected from a single honeybee corbicula was sufficient for genome‐skimming. We conclude that genome‐skimming is a feasible approach to identifying and quantifying mixed pollen samples. By providing reliable and sensitive taxon identification and relative abundance, this method is expected to improve our understanding in studies that involve plant‐pollinator interactions, such as pollen preference in corbiculate bees, pollen diet analyses, identification of landscape pollen resource use from bee hives. This article is protected by copyright. All rights reserved.
... Multiple mechanisms may explain the declines in body size along landscape gradients including reduced floral resource availability (Kim, 1999;Peterson & Roitberg, 2006a, 2006b, increased pesticide exposure (Bernauer et al., 2015) and even competition with managed bees (Goulson & Sparrow, 2009 F I G U R E 1 Mean body size (±SE) measured as the intertegular distance (ITD) of bees collected from sites with and without a local habitat enhancement. Asterisks indicate significant pairwise differences at *p < 0.1, **p < 0.05, and ***p < 0.01 ...
The negative effects of landscape simplification on bee communities are well documented. To reverse these effects, flowering habitat enhancements are designed to provide supplemental nutritional resources for wild bees and are particularly important when few resources are available in the surrounding landscape. Yet, it is not known whether or how habitat enhancements support bee populations under varying landscape contexts. Body size is a morphological trait that is strongly linked to foraging ability, immune function, and fitness in bees. Landscape simplification has been associated with size declines across bee taxa, and smaller body size can be an early indicator of environmental stress. To determine whether the negative effects of landscape simplification on body size can be improved by adding floral resources to farm landscapes, we measured the body size of ten wild bee species collected at 70 sites with or without habitat enhancements in Michigan and New York. Bees were collected at sites with varying amounts of agriculture in the surrounding landscape, allowing us to test whether morphological responses to enhancements are affected by landscape simplification. Half of the bee species measured exhibited declining body size across the landscape gradient. Among these species, declines were buffered by the presence of habitat enhancements suggesting this response is the result of improved nutrition, reduced need for long‐distance foraging, enhanced recruitment of larger individuals or a combination of these mechanisms. Declines in body size were strongest in both the smallest and the largest species. Large and medium sized species exhibited the greatest response to flowering habitat enhancements. Synthesis and applications. At sites with high agricultural cover, we observed intraspecific body size declines among many species; however, we did not observe decreased body size in any species at sites with a flowering habitat enhancement. Therefore, our findings suggest that the presence of flowering habitat enhancements can support wild bees experiencing stress from intensively managed agricultural landscapes across multiple cropping systems and regions. This article is protected by copyright. All rights reserved.
... Although orchards may provide large amounts of pollen and nectar during flowering season, high densities of honeybee hives are usually placed during flowering. Due to these unnaturally high densities (Geldmann and González-varo 2018), bumblebees and other wild pollinators may suffer from competition with honeybees (Thomson 2004;Goulson and Sparrow 2009;Shavit et al. 2009, but see Steffan-Dewenter and Tscharntke 2000) or pathogen spillover (Fürst et al. 2014). The negative effect of competition with honeybees is stronger in homogeneous landscapes (Herbertsson et al. 2016), making bumblebees in intensive agricultural landscapes dominated by orchards more susceptible than in more diverse agrolandscapes. ...
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.
... One concern with widespread adoption of the beehive fences is that they may locally increase the density of honeybees to the extent that they outcompete other ecologically important bee species (Martins 2004). Honeybees (Apis mellifera L.) are native to Kenya, but they are also strong competitors in the floral resource market (Thomson 2004) even in their native range (Goulson and Sparrow 2009;Herbertsson et al. 2016). In places where the honeybee is considered invasive, there is mixed evidence that it may or may not compete with native wild bees for pollen and nectar (Roubik and Wolda 2001;Paini 2004;Paini and Roberts 2005;Badano and Vergara 2011). ...
... Er is in deze studie een negatief verband gevonden tussen het aantal honingbijen en wilde bijen in een transecttelling (Fig. 6). Dit is in lijn met andere studies die aantonen dat honingbijen concurreren met wilde bijen om de (vaak schaars) beschikbare voedselbronnen (Forup & Memmott 2005;Goulson & Sparrow 2009). Het is daarom sterk aan te bevelen om geen honingbijkasten te plaatsen nabij Vogelakkers en hier terreineigenaren en imkers op aan te spreken. ...
Volunteers monitored the abundance of hoverflies and bees in multi-year agri-environment measures called 'Vogelakkers'. Monitoring took place in the north of the Netherlands in 2017 and 2018, was based on transect counts of abundance of four groups of bees and nine groups of hoverflies.
Body size is arguably one of the most important traits influencing the physiology and ecology of animals. Shifts in animal body size have been observed in response to climate change, including in bumble bees (Bombus spp. [Hymenoptera: Apidae]). Bumble bee size shifts have occurred concurrently with the precipitous population declines of several species, which appear to be related, in part, to their size. Body size variation is central to the ecology of bumble bees, from their social organization to the pollination services they provide to plants. If bumble bee size is shifted or constrained, there may be consequences for the pollination services they provide and for our ability to predict their responses to global change. Yet, there are still many aspects of the breadth and role of bumble bee body size variation that require more study. To this end, we review the current evidence of the ecological drivers of size variation in bumble bees and the consequences of that variation on bumble bee fitness, foraging, and species interactions. In total we review: (1) the proximate determinants and physiological consequences of size variation in bumble bees; (2) the environmental drivers and ecological consequences of size variation; and (3) synthesize our understanding of size variation in predicting how bumble bees will respond to future changes in climate and land use. As global change intensifies, a better understanding of the factors influencing the size distributions of bumble bees, and the consequences of those distributions, will allow us to better predict future responses of these pollinators.
Pollinators’ climate change impact assessments focus mainly on mainland regions. Thus, we are unaware how island species might fare in a rapidly changing world. This is even more pressing in the Mediterranean Basin, a global biodiversity hotspot. In Greece, a regional pollinator hotspot, climate change research is in its infancy and the insect Wallacean shortfall still remains unaddressed. In a species distribution modelling framework, we used the most comprehensive occurrence database for bees in Greece to locate the bee species richness hotspots in the Aegean, and investigated whether these might shift in the future due to climate change and assessed the Natura 2000 protected areas network effectiveness. Range contractions are anticipated for most taxa, becoming more prominent over time. Species richness hotspots are currently located in the NE Aegean and in highly disturbed sites. They will shift both altitudinally and latitudinally in the future. A small proportion of these hotspots are currently included in the Natura 2000 protected areas network and this proportion is projected to decrease in the coming decades. There is likely an extinction debt present in the Aegean bee communities that could result to pollination network collapse. There is a substantial conservation gap in Greece regarding bees and a critical re-assessment of the established Greek protected areas network is needed, focusing on areas identified as bee diversity hotspots over time.
Concern around declining bee populations globally has become an environmental issue of mainstream importance. Policymakers, scientists, environmental non-government organizations, media outlets and the public have displayed great interest in conservation actions to support pollinators. As with many environmental causes, green washing, or in this case ‘bee washing’, has become rampant. Bee washing can lead to multiple negative consequences, including misinformation, misallocation of resources, increasing threats and steering public understanding and environmental policy away from evidence-based decision-making. Here I will discuss the multiple potential consequences of bee washing on efforts to conserve declining wild bees and promote wild bee health.
Confrontés aux demandes grandissantes d’installations de ruches, les gestionnaires d’aires protégées s’interrogent sur les conséquences d’une densité élevée d’abeilles domestiques sur les communautés d’abeilles sauvages. Pour répondre à cette question, au sein du Parc national des Calanques, nous avons inventorié la diversité des espèces de pollinisateurs, leurs traits écologiques, et leurs interactions avec la flore sauvage. À travers un bilan des campagnes de terrain réalisées sur une période de 10 ans, près de 250 espèces de pollinisateurs (Apoidea, Syrphidae et Bombyliidae) ont été répertoriées. Les communautés d'abeilles sauvages étaient sensibles à l’occupation du sol à l’échelle du paysage à 1km. La richesse spécifique et l’abondance des grandes abeilles sauvages diminuaient avec l’augmentation de la densité de colonies d’abeilles domestiques suggérant une compétition pour les ressources florales. Ce résultat a été confirmé à travers l’observation des comportements de butinage des abeilles domestiques et sauvages et s’est manifesté par une exclusion compétitive des grandes abeilles sauvages et un changement de régime alimentaire des petites abeilles sauvages et des bourdons. Enfin, la quantité de ressources florales disponibles (nectar et pollen) estimée à l’échelle du Parc national des Calanques n’est pas suffisante pour couvrir les besoins alimentaires des abeilles domestiques déjà installées. Aux vues de l’importance des habitats protégés méditerranéens pour les communautés de pollinisateurs sauvages, cette thèse propose des préconisations de gestion visant à concilier la pratique de l’apiculture avec le maintien de la faune de pollinisateurs sauvages.
Petition to list the variable cuckoo bumble bee (Bombus variabilis) to the Endangered Species Act.
Wild bees are in decline on a local to global scale. The presence of managed honey bees can lead to competition for resources with wild bee species, which has not been investigated so far for human-modified landscapes. In this study we assess if managed honey bee hive density influence nest development (biomass) of bumble bees, an important trait affecting fitness. We hypothesize that domesticated honey bees can negatively affect Bombus terrestris nest development in human-modified landscapes. In Flanders, Belgium, where such landscapes are dominantly present, we selected 11 locations with landscape metrics ranging from urban to agricultural. The bee hive locations were mapped and each location contained one apiary dense (AD) and one apiary sparse (AS) study site (mean density of 7.6 ± 5.7 managed honey bee hives per km2 in AD sites). We assessed the effect of apiary density on the reproduction of reared B. terrestris nests. Reared B. terrestris nests had more biomass increase over 8 weeks in apiary sparse (AS) sites compared to nests located in apiary dense (AD) sites. This effect was mainly visible in urban locations, where nest in AS sites have 99.25 ± 60.99 g more biomass increase compared to nest in urban AD sites. Additionally, we found that managed bumble bee nests had higher biomass increase in urban locations. We conclude that the density of bee hives is a factor to consider in regard to interspecific competition between domesticated honey bees and bumble bees.
Pollinator conservation is a major focus of current conservation attention and public policy. However, an understanding of the social dimensions of pollinator conservation is urgently needed for effective action. In 2014, Ontario became the first jurisdiction in North America to propose to regulate neonicotinoid pesticides, and the proposal included a draft Pollinator Health Action Plan with additional measures to protect pollinator species. We analyzed the 972 comments submitted on the proposal by individual citizens, determining each commenter’s stance, source of information (if applicable), and main concerns. We found very strong support for neonicotinoid regulation, with less than 5% opposed. We also found that the greatest concerns were for bees and pollination services, but that the diversity of pollinating species and the relative contributions of various taxa to pollination was not well understood. Government regulation of neonicotinoid pesticides and other actions to protect pollinator health clearly have the broad support and great interest of the general public, which creates a rare opportunity for conservation policy and action. We conclude that, in order to be effective, broad support will need to be translated into nuanced, evidence-based policy that is focussed on native species and addresses the many threats at-risk pollinators face.
MMA - ONU Medio Ambiente. 2018. Estudio de Caso: Determinación del Servicio
Ecosistémico de Polinización de Artrópodos Nativos en Agroecosistemas, de la
Localidad de Caleu, Til-Til. Basado en investigación encargado a: PhD. Víctor Monzón y PhD. Luisa Ruz, Universidad Católica del Maule y Pontificia Universidad Católica de Valparaíso. Financiado en el marco del proyecto GEFSEC ID 5135 Ministerio del Medio Ambiente - ONU Medio ambiente. Santiago, Chile. 86pp.
Zapylanie kwiatów jest jednym z kluczowych procesów gwarantujących reprodukcję roślin kwiatowych, a przez to stabilność ekosystemów lądowych. Biorąc pod uwagę pogłębiający się kryzys zapyleń oraz spadek bioróżnorodności wśród owadów, powinniśmy przyjrzeć się ich przyczynom i okolicznościom. Niestety, są one na ogół rozpatrywane jedynie w kontekście wymierania rodzin pszczoły miodnej (Apis mellifera), będącej jednym z blisko 20.000 gatunków pszczół na świecie. Uważana za jednego z najlepszych zapylaczy dla wielu gatunków, pszczoła miodna jest jednak w rzeczywistości owadem o niejednoznacznej roli ekosystemowej. Badania wskazują na jej wysoką konkurencyjność w stosunku do dzikich gatunków zapylaczy, które mogą być niezwykle efektywnymi wektorami pyłku. Bazując na współczesnej wiedzy należy stanowczo stwierdzić, że propagowanie pszczelarstwa nie może być jedyną metodą na ograniczenie globalnego kryzysu zapyleń, a zwiększanie liczby rodzin pszczelich nie jest odpowiedzią na spadek bioróżnorodności. Aby zatem zrównoważyć potrzeby ochrony bioróżnorodności, bezpieczeństwa żywnościowego i interesy pszczelarzy, niezbędny jest mądry kompromis, oparty na rzetelnych danych naukowych.
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 Interspecific competition for a limited resource can result in the reduction of survival, growth and/or reproduction in one of the species involved. The introduced honey bee (Apis mellifera Linnaeus) is an example of a species that can compete with native bees for floral resources. Often, research into honey bee/native bee competition has focused on floral resource overlap, visitation rates or resource harvesting, and any negative interaction has been interpreted as a negative impact. Although this research can be valuable in indicating the potential for competition between honey bees and native bees, to determine if the long-term survival of a native bee species is threatened, fecundity, survival or population density needs to be assessed. The present review evaluates research that has investigated all these measurements of honey bee/native bee competition and finds that many studies have problems with sample size, confounding factors or data interpretation. Guidelines for future research include increasing replication and using long-term studies to investigate the impact of both commercial and feral honey bees.
Size polymorphism is an important life history trait in bumblebees with strong impact on individual behavior and colony organization. Within a colony larger workers tend to serve as foragers, while smaller workers fulfill inhive tasks. It is often assumed that size-dependent division of labor relates to differences in task performance. In this study we examined size-dependent interindividual variability in foraging, i.e. whether foraging behavior and foraging capability of bumblebee workers are affected by their size. We observed two freely foraging Bombus terrestris colonies and measured i) trip number, ii) trip time, iii) proportion of nectar trips, and iv) nectar foraging rate of different sized foragers. In all observation periods large foragers exhibited a significantly higher foraging rate than small foragers. None of the other three foraging parameters was affected by worker size. Thus, large foragers contributed disproportionately more to the current nectar influx of their colony. We provide a detailed discussion of the possible proximate mechanisms underlying the differences in foraging rate.
Diapause survival and post-diapause performance (i.e., if a queen starts to lay eggs) of in total 2210 bumblebee queens (Bombus terrestris) were measured under different diapause regimes: 5 temperatures (−5, 0, 5, 10 and 15 °C) in combination with 5 durations of exposure (1, 2, 4, 6 and 8 months).
The results show that weight at the start of diapause determines to a large extent whether a queen will be able to survive diapause. Queens with a wet weight below 0.6 g prior to diapause did not survive, but for those queens exceeding this threshold a higher pre- diapause weight did not increase their post-diapause performance.
There was no effect of temperature on diapause survival; 76% of the variance in survival could be explained by the duration of the treatment. Neither temperature nor duration of exposure had an effect on post-diapause performance. The preoviposition period of the queens that laid eggs was also determined. The preoviposition period was affected by both temperature and duration of exposure: the preoviposition period decreased with decreasing temperature but also with increasing duration of the treatment.
Bumblebee workers vary greatly in size, unlike workers of most other social bees. This variability has not been adequately explained. In many social insects, size variation is adaptive, with different-sized workers performing different tasks (alloethism). Here we established whether workers of the bumblebee, Bombus terrestris (L.) (Hymenoptera; Apidae), exhibit alloethism. We quantified the size of workers engaging in foraging compared to those that remain in the nest, and confirmed that it is the larger bees that tend to forage (X±SE thorax widths 4.34±0.01 mm for nest bees and 4.93±0.02 mm for foragers). We then investigated whether large bees are better suited to foraging because they are able to transport heavier loads of food back to the nest. Both pollen and nectar loads of returning foragers were measured, demonstrating that larger bees do return with a heavier mass of forage. Foraging trip times were inversely related to bee size when collecting nectar, but were unrelated to bee size for bees collecting pollen. Overall, large bees brought back more nectar per unit time than small bees, but the rate of pollen collection appeared to be unrelated to size. The smallest foragers had a nectar foraging rate close to zero, presumably explaining why foragers tend to be large. Why might larger bees be better at foraging? Various explanations are considered: larger bees are able to forage in cooler conditions, may be able to forage over larger distances, and are perhaps also less vulnerable to predation. Conversely, small workers are presumably cheaper to produce and may be more nimble at within-nest tasks. Further research is needed to assess these possibilities. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.
The increasing numbers of endangered wild bee species highlights the need for quantifying potential adverse effects of foraging honeybees. We analysed the response of bumblebees at genus and species level to experimentally increased honeybee density. The study was carried out on a Phacelia tanacetifolia field and adjacent patches of wild plants located in an agricultural landscape. Addition of one or ten A. m. ligustica colonies substantially increased total honeybee density not only on Phacelia but also on neighbouring patches of wild plants. The response of bumblebees (Bombus spp.) differed among species. Only minor spatial changes in the abundance of the short-tongued B. terrestris-group were observed on Phacelia. At wild plant patches, the B. lapidarius-group and the longer tongued bumblebee species (B. muscorum, B. sylvarum, B. pascuorum) responded with a shift between plant species. Limitations of competition avoidance in flower-impoverished landscapes are discussed.
Bumblebees are major pollinators of crops and wildflowers in northern temperate regions. Knowledge of their ecology is vital for the design of effective management and conservation strategies but key aspects remain poorly understood. Here we employed microsatellite markers to estimate and compare foraging range and nest density among four UK species: Bombus terrestris, Bombus pascuorum, Bombus lapidarius, and Bombus pratorum. Workers were sampled along a 1.5-km linear transect across arable farmland. Eight or nine polymorphic microsatellite markers were then used to identify putative sisters. In accordance with previous studies, minimum estimated maximum foraging range was greatest for B. terrestris (758 m) and least for B. pascuorum (449 m). The estimate for B. lapidarius was similar to B. pascuorum (450 m), while that of B. pratorum was intermediate (674 m). Since the area of forage available to bees increases as the square of foraging range, these differences correspond to a threefold variation in the area used by bumblebee nests of different species. Possible explanations for these differences are discussed. Estimates for nest density at the times of sampling were 29, 68, 117, and 26/km2 for B. terrestris, B. pascuorum, B. lapidarius and B. pratorum, respectively. These data suggest that even among the most common British bumblebee species, significant differences in fundamental aspects of their ecology exist, a finding that should be reflected in management and conservation strategies.
The floral sources of pollen and nectar used by honey bees in Ireland were studied during 1991-1994 by regular two-weekly sampling of pollen pellets from three colonies at a single site, and pollen and nectar samples from four individual colonies at different sites located in mid-western Ireland. Samples were analysed using dry weight and pollen analysis; relative abundance of pollen types was expressed as a percentage of the total number of pollen grains counted and presented as dominance-diversity curves. At the single site, 76 pollen types were identified and a seasonal variation in the dominance of species was apparent. The diversity of species being foraged reached a maximum during June and July. Native nectariferous species were the most important pollen sources, while pollen was also gathered from introduced and entomophilous/anemophilous species especially during spring and early summer. Trees and shrubs were important pollen sources early in the year while herbs and shrubs increased in importance during summer and autumn. A total of 92 pollen types were identified in the pollen and nectar samples at four different sites and this indicates the diversity of plant species foraged by honey bees and the importance of different species as pollen sources, nectar sources or pollen and nectar sources. Honey bee preferences for certain species and individual colony preferences are discussed.
Abstract Bees are generally regarded as beneficial insects for their role in pollination, and in the case of the honeybee Apis mellifera, for production of honey. As a result several bee species have been introduced to countries far beyond their home range, including A. mellifera, bumblebees (Bombus sp.), the alfalfa leafcutter bee Megachile rotundata, and various other solitary species. Possible negative consequences of these introductions include: competition with native pollinators for floral resources; competition for nest sites; co-introduction of natural enemies, particularly pathogens that may infect native organisms; pollination of exotic weeds; and disruption of pollination of native plants. For most exotic bee species little or nothing is known of these possible effects. Research to date has focused mainly on A. mellifera, and has largely been concerned with detecting competition with native flower visitors. Considerable circumstantial evidence has accrued that competition does occur, but no experiment has clearly demonstrated long-term reductions in populations of native organisms. Most researchers agree that this probably reflects the difficulty of carrying out convincing studies of competition between such mobile organisms, rather than a genuine absence of competitive effects. Effects on seed set of exotic weeds are easier to demonstrate. Exotic bees often exhibit marked preferences for visiting flowers of exotic plants. For example, in Australia and New Zealand many weeds from Europe are now visited by European honeybees and bumblebees. Introduced bees are primary pollinators of a number of serious weeds. Negative impacts of exotic bees need to be carefully assessed before further introductions are carried out.
Captive colonies of Bombus terricola Kirby received pollen for 8, 14, or 24 h per day from the time of onset of second brood oviposition until colony decline. The pattern of change of worker body size over time, especially between the first and second broods, varied according to these experimental food regimes. The results indicate that conflicting results reported in the literature, with respect to changes in worker size over the course of colony development, probably can be regarded, at least in part, as the outcome of differences in food supply.
Six field colonies and four laboratory colonies of bumblebees were used in a marking experiment during the summer of 1964 in Wisconsin to study the seasonal size increase of the workers. Mean sizes of weekly age groups differed significantly. The workers gradually increased in size in healthy colonies. In colonies disrupted by parasitism or transfer from the field to the laboratory, consecutive age groups of workers were- significantly smaller. After a period of adjustment, the colonies transferred from the field to the laboratory resumed the normal pattern of worker size increase.
Biological invasions represent both an increasingly important applied problem and a tool for gaining insight into the structure of ecological communities. Although competitive interactions between invasive and native species are considered among the most important mechanisms driving invasion dynamics, such interactions are in general poorly understood. The European honey bee (Apis mellifera) is a widespread and economically important invader long suspected to competitively suppress many native bee species. Yet the extent to which this introduced species alters native communities remains controversial, reflecting ongoing debate over the importance of resource competition in regulating pollinator populations. I experimentally tested the effects of competition with Apis on colony foraging behavior and reproductive success of a native eusocial bee, Bombus occidentalis Greene, in coastal California. B. occidentalis colonies located near experimentally introduced Apis hives had lower mean rates of forager return and a lower ratio of foraging trips for pollen relative to nectar. Both male and female reproductive success of B. occidentalis were also reduced with greater proximity to introduced Apis hives. Reproductive success correlated significantly with measures of colony foraging behavior, most strongly with the relative allocation of foraging effort to pollen collection. This pattern suggests that B. occidentalis colonies exposed to competition with Apis experienced increased nectar scarcity and responded by reallocating foragers from pollen to nectar collection, resulting in lowered rates of larval production. These results provide evidence that Apis competitively suppresses a native social bee known to be an important pollinator, with the potential for cascading effects on native plant communities. This work also contributes to a greater understanding of the role competitive interactions play in pollinator communities, particularly for social bees.
It is well known that introducing non-native organisms can have disastrous consequences, be they cane toads and prickly pear in Australia or grey squirrels and Himalayan balsam in the UK. Many countries now have strict quarantine controls to prevent further introductions.Yet we have something of a blind spot for bees. Because they are widely regarded as beneficial, bees of various species continue to be introduced outside their native range; only rarely and recently have serious objections been raised.
Bumblebees (Hymenoptera: Apidae) are important pollinators of crops and wildflowers, but many species have suffered dramatic declines in recent decades. Strategies for their conservation require knowledge of their foraging range and nesting density, both of which are poorly understood. Previous studies have mainly focussed on the cosmopolitan bumblebee species Bombus terrestris, and implicitly assume this to be representative of other species. Here we use a landscape-scale microsatellite study to estimate the foraging range and nesting density of two ecologically dissimilar species, B. terrestris and B. pascuorum. Workers were sampled along a 10 km linear transect and 8–9 polymorphic microsatellite markers used to identify putative sisters. We provide the first published estimates of the number of colonies using a circle of radius 50 m in an agricultural landscape: 20.4 for B. terrestris and 54.7 for B. pascuorum. Estimates of nest density differed significantly between the two species: 13 km−2 for B. terrestris and 193 km−2 for B. pascuorum. Foraging ranges also differed substantially, with B. pascuorum foraging over distances less than 312 m and B. terrestris less than 625 m. Clearly bumblebee species differ greatly in fundamental aspects of their ecology. This has significant implications for the development of conservation strategies for rare bumblebees and isolated plant populations, for the management of bumblebees as pollinators, and for predicting patterns of gene flow from genetically modified plants.
The development of worker, male, and queen larvae of Bombus terrestris was analysed by measuring their mass and the amount of pollen they had ingested. The three kinds of larvae grew significantly differently. Workers and queens differed strongly in their growth from the beginning of the larval stage. On the other hand, males and queens were more similar in their development. Furthermore, during the later stages, pollen played a less important role in the increase of the queens' mass, which indicates that a different mechanism is probably involved in their growth. Two hypotheses are discussed: either there is a difference in the queens' metabolism or they receive a different diet, which improves their growth.
Developing tools for rapid assessment of introduced species impacts is one of the most important challenges in invasion ecology. Most assessments of impact rely on correlational data or other indirect measures. Yet few studies have evaluated invasion effects using multiple, simultaneously applied monitoring and experimental approaches, in order to compare easily obtained metrics with more difficult but direct measures of reproductive success or population dynamics. In this study, I use data from an experimental test of introduced honey bee (Apis mellifera) impacts on native bumble bees (Bombus spp.) to address two major questions: 1) how well did observational data on niche overlap and spatial correlations between Apis and Bombus predict the results of experimental tests of competitive effects? and 2) how well did effects of the experimental Apis manipulations on Bombus foragers, which are easy to observe, predict changes in reproductive success of colonies, which are difficult to measure? Niche overlap between Apis and Bombus varied substantially, but increased to levels as high as 80–90% during periods of resource scarcity. Correlations between numbers of Apis foragers and numbers of Bombus foragers were also highly variable, but I detected a significant negative relationship in only one of the seven months observed. In contrast, the experimental results showed that mean numbers of Bombus foragers observed on a given transect increased significantly with greater distance from introduced Apis colonies. Of these three measures (niche overlap, correlations in abundances, and effects of experimental introductions), only the experimental data on forager abundances accurately estimated competitive effects on colony reproductive success previously reported for the same experiment, and the correlational data in particular completely failed to predict the effects observed in the experimental study. This work suggests that great caution is warranted in making assessments of invasion impact on the basis of spatial or temporal correlations between invasive and native species. Thus, investing in even small and limited experimental studies may be more valuable than extensive observational work in quantifying invasion impacts.
s Abstract Bees are generally regarded as beneficial insects for their role in pol-lination, and in the case of the honeybee Apis mellifera, for production of honey. As a result several bee species have been introduced to countries far beyond their home range, including A. mellifera, bumblebees (Bombus sp.), the alfalfa leafcutter bee Megachile rotundata, and various other solitary species. Possible negative conse-quences of these introductions include: competition with native pollinators for floral resources; competition for nest sites; co-introduction of natural enemies, particularly pathogens that may infect native organisms; pollination of exotic weeds; and disrup-tion of pollination of native plants. For most exotic bee species little or nothing is known of these possible effects. Research to date has focused mainly on A. mellifera, and has largely been concerned with detecting competition with native flower visitors. Considerable circumstantial evidence has accrued that competition does occur, but no experiment has clearly demonstrated long-term reductions in populations of native or-ganisms. Most researchers agree that this probably reflects the difficulty of carrying out convincing studies of competition between such mobile organisms, rather than a genuine absence of competitive effects. Effects on seed set of exotic weeds are easier to demonstrate. Exotic bees often exhibit marked preferences for visiting flowers of exotic plants. For example, in Australia and New Zealand many weeds from Europe are now visited by European honeybees and bumblebees. Introduced bees are primary pollinators of a number of serious weeds. Negative impacts of exotic bees need to be carefully assessed before further introductions are carried out.
Summary 1. In contrast to other social bees, bumble-bees exhibit considerable size variation within the worker caste. This size variation has not been adequately explained, although it is known that larger workers tend to be foragers and smaller bees spend more time in the nest. We quantify size variation and mean size for foragers of 22 bumble- bee species inhabiting climates ranging from arctic and montane to the lowland tropics. 2. Mean size was larger in bee species from cold climates compared with temperate bumble-bees. Within species, individuals from Scotland tended to be larger than those from southern England. However, tropical bumble-bees (mostly belonging to the sub- genus Fervidobombus ) were largest of all. We suggest that although a lower limit to size may be imposed by inhabiting cold climates, overheating does not constrain large size in bumble-bees from hot climates, perhaps because they have efficient mechanisms for heat loss through shunting heat to their extremities. 3. Tropical bees had shorter thoracic setae than species from cooler climates, while B. terrestris from Greece had shorter setae than those from southern UK. Presumably shorter setae enhance heat loss in warm climates. 4. Larger workers of B. terrestris were found to have smaller extremities, in proportion to their size, than small workers. We suggest that heat retention is more important in large bees that spend more of their time foraging, than in small bees which spend much of their time in the nest where incubation of the brood requires them to lose heat. 5. In the temperate climate of southern UK, we found no evidence for ambient tem- perature having a differential effect on activity of workers of B. terrestris according to their size. We suggest that, at least in temperate climates, size variation in bumble-bee foragers is probably not an adaptation to temperature variation. Instead it may improve colony foraging efficiency since foragers of different sizes are suited to, and tend to visit, different flower species.
1. It has long been known that foraging bumblebee workers vary greatly in size, within species, and within single nests. This phenomenon has not been adequately explained. Workers of their relatives within the Apidae exhibit much less size variation.2. For the bumblebee Bombus terrestris size, as measured by thorax width, was found to correspond closely with tongue length, so that larger bees are equipped to feed from deeper flowers.3. The mean size of worker bees attracted to flowers was found to differ between plant species, and larger bees with longer tongues tended to visit deeper flowers.4. Finally, handling time depended on the match between corolla depth and tongue length: large bees were slower than small bees when handling shallow flowers, but quicker than small bees when handling deep flowers.5. Size variation within bumblebees may be adaptive, since it enables the colony as a whole to efficiently exploit a range of different flowers. Possible explanations for the marked differences in size variation exhibited by bumblebees compared with Apis species and stingless bees (Meliponinae) are discussed.
This study examines factors that affect foraging rate of free-flying bumblebees, Bombus terrestris, when collecting nectar, and also what factors determine whether they collect pollen or nectar. We show that nectar foraging rate (mass gathered per unit time) is positively correlated with worker size, in accordance with previous studies. It has been suggested that the greater foraging rate of large bees is due to their higher thermoregulatory capacity in cool conditions, but our data suggest that this is not so. Workers differing in size were not differentially affected by the weather. Regardless of size, nave bees were poor foragers, often using more resources than they gathered. Foraging rate was not maximised until at least 30 trips had been made from the nest. Foraging rates were positively correlated with humidity, perhaps because nectar secretion rates were higher or evaporation of nectar lower at high humidity. Temperature, wind speed and cloud cover did not significantly influence foraging rate, within the summertime range that occurred during the study. Weather greatly influenced whether bees collected pollen or nectar. Pollen was preferably collected when it was warm, windy, and particularly when humidity was low; and preferably during the middle of the day. We suggest that bees collect pollen in dry conditions, and avoid collecting pollen when there is dew or rain-water droplets on the vegetation, which would make grooming pollen into the corbiculae difficult. Availability of sufficient dry days for pollen collection may be an important factor determining the success of bumblebee colonies.
Lantana camara, a woody shrub originating in south and central America, is among the most widespread and troublesome exotic weeds of the old-world tropics. It invades pasture, crops and native ecosystems, causing substantial economic losses and environmental degradation. In Australia alone, L. camara is currently estimated to cover approximately 40,000 km2. In glasshouse studies we demonstate that L. camara requires cross-pollination to set fruit, and that honeybee visits result in effective pollination. Field studies carried out in Queensland, Australia, suggest that fruit set is limited by pollinator abundance, and that the main pollinator of L. camara throughout a substantial portion of its Australian range appears to be the honeybee, Apis mellifera. Seed set was strongly correlated with honeybee abundance, and at many sites, particularly in southern Queensland, honeybees were the only recorded flower visitors. Of 63 sites that were visited, seed set was highest at five sites where only honeybees were present. Hives are frequently stationed within and adjacent to areas such as National Parks that are threatened by this noxious weed. Management of honeybee populations may provide a powerful tool for cost-effective control of L. camara that has previously been overlooked. We suggest that there are probably many other weeds, both in Australia and elsewhere, that benefit from honeybee pollination.
Declines in bumble bee species in the past 60 years are well documented in Europe, where they are driven primarily by habitat loss and declines in floral abundance and diversity resulting from agricultural intensification. Impacts of habitat degradation and fragmentation are likely to be compounded by the social nature of bumble bees and their largely monogamous breeding system, which renders their effective population size low. Hence, populations are susceptible to stochastic extinction events and inbreeding. In North America, catastrophic declines of some bumble bee species since the 1990s are probably attributable to the accidental introduction of a nonnative parasite from Europe, a result of global trade in domesticated bumble bee colonies used for pollination of greenhouse crops. Given the importance of bumble bees as pollinators of crops and wildflowers, steps must be taken to prevent further declines. Suggested measures include tight regulation of commercial bumble bee use and targeted use of environmentally comparable schemes to enhance floristic diversity in agricultural landscapes.
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