| 1. |
- Bolin, Arvid, et al.
(författare)
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Scale-dependent foraging tradeoff allows competitive coexistence
- 2018
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Ingår i: Oikos. - : Wiley. - 0030-1299. ; 127:11, s. 1575-1585
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Tidskriftsartikel (refereegranskat)abstract
- In spatially heterogeneous environments, coexistence between competing species can be facilitated by spatially mediated tradeoffs. In this paper we develop a mechanistic model to investigate under which circumstances interspecific differences in the tradeoff between foraging efficiency and travel costs can allow two central place foraging species to coexist in spite of considerable overlap in resource use. One species (Flyer) has a high basal metabolic rate, but a low relative cost of travelling such that it can use patches at a greater distance from its central place while the minimum patch quality it can economically use is high. The other species (Forager), by contrast, has a lower basal metabolic rate, but higher relative cost of travelling, and can therefore be a more efficient forager and able to use foraging patches of low quality, as long as they are not too far from the nest. We demonstrate that the coexistence of these two species critically depends on landscape composition and structure, with the Flyer outcompeting the Forager in structurally simple, coarse-grained, landscapes with abundant high-quality forage and the Forager outcompeting the Flyer in fine-grained highly diverse landscapes. Coexistence between the two species is possible when the landscape is structurally and compositionally complex, fine-grained, and has both high and low quality forage. Our results demonstrate that exploitative competition between two contrasting life histories can produce very different community dynamics depending on landscape composition and structure.
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| 2. |
- Lonsdorf, Eric V, et al.
(författare)
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A spatially explicit model of landscape pesticide exposure to bees : Development, exploration, and evaluation
- 2024
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Ingår i: Science of the Total Environment. - 1879-1026. ; 908
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Tidskriftsartikel (refereegranskat)abstract
- Pesticides represent one of the greatest threats to bees and other beneficial insects in agricultural landscapes. Potential exposure is generated through compound- and crop-specific patterns of pesticide use over space and time and unique degradation behavior among compounds. Realized exposure develops through bees foraging from their nests across the spatiotemporal mosaic of floral resources and associated pesticides throughout the landscape. Despite the recognized importance of a landscape-wide approach to assessing exposure, we lack a sufficiently-evaluated predictive framework to inform mitigation decisions and environmental risk assessment for bees. We address this gap by developing a bee pesticide exposure model that incorporates spatiotemporal pesticide use patterns, estimated rates of pesticide degradation, floral resource dynamics across habitats, and bee foraging movements. We parameterized the model with pesticide use data from a public database containing crop-field- and date-specific records of uses throughout our study region over an entire year. We evaluate the model performance in predicting bee pesticide exposure using a dataset of pesticide residues in pollens gathered by bumble bees (Bombus vosnesenskii) returning to colonies across 14 spatially independent landscapes in Northern California. We applied alternative model formulations of pesticide accumulation and degradation, floral resource seasonality, and bee foraging behavior to evaluate different levels of detail for predicting observed pesticide exposure. Our best model explained 73 % of observed variation in pesticide exposure of bumble bee colonies, with generally positive correlations for the dominant compounds. Timing and location of pesticide use were integral, but more detailed parameterizations of pesticide degradation, floral resources, and bee foraging improved the predictions little if at all. Our results suggest that this approach to predict bees' pesticide exposure has value in extending from the local field scale to the landscape in environmental risk assessment and for exploring mitigation options to support bees in agricultural landscapes.
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| 3. |
- Nicholson, Charlie C., et al.
(författare)
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Flowering resources distract pollinators from crops : Model predictions from landscape simulations
- 2019
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 56:3, s. 618-628
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Tidskriftsartikel (refereegranskat)abstract
- Enhancing floral resources is a widely accepted strategy for supporting wild bees and promoting crop pollination. Planning effective enhancements can be informed with pollination service models, but these models should capture the behavioural and spatial dynamics of service-providing organisms. Model predictions, and hence management recommendations, are likely to be sensitive to these dynamics. We used two established models of pollinator foraging to investigate whether habitat enhancement improves crop visitation; whether this effect is influenced by pollinator foraging distance and landscape pattern; and whether behavioural detail improves model predictions. The more detailed central place foraging model better predicted variation in bee visitation observed between habitat types, because it includes optimized trade-offs between patch quality and distance. Both models performed well when predicting visitation rates across broader scales. Using real agricultural landscapes and simulating habitat enhancements, we show that additional floral resources can have diverging effects on predicted crop visitation. When only co-flowering resources were added, optimally foraging bees concentrated in enhancements to the detriment of crop pollination. For both models, adding nesting resources increased crop visitation. Finally, the marginal effect of enhancements was greater in simple landscapes. Synthesis and applications. Model results help to identify the conditions under which habitat enhancements are most likely to increase pollination services in agriculture. Three design principles for pollinator habitat enhancement emerge: (a) enhancing only flowers can diminish services by distracting pollinators away from crops, (b) providing nesting resources is more likely to increase bee populations and crop visitation and (c) the benefit of enhancements will be greatest in landscapes that do not already contain abundant habitat.
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| 4. |
- Nicholson, Charlie C., et al.
(författare)
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Landscapes of risk : A comparative analysis of landscape metrics for the ecotoxicological assessment of pesticide risk to bees
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Ingår i: Journal of Applied Ecology. - 0021-8901.
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Tidskriftsartikel (refereegranskat)abstract
- Pesticide use in agricultural landscapes creates environmental contamination that is heterogenous in space and time. Mobile organisms, such as bees, are exposed to multiple contamination sources when visiting patches that vary in the amount, timing and toxicity of pesticides used. Yet, environmental risk assessments (ERA) typically fail to consider this heterogeneity, in part because of the complexities of estimating exposure to different pesticides, and subsequent risk at organism-relevant scales. We use pesticide assays of 269 bee-collected pollen samples to understand the spatiotemporal variability of risk across a network of 41 field sites in southern Sweden. Observed bee pesticide risk is calculated based on compound-specific residue quantifications in pollen and standardized toxicity data. We then compare the ability of three classes of landscape-scale variables to predict this risk: (1) landscape composition and configuration metrics, (2) landscape load based on national pesticide use data and (3) predictions from a newly developed bee pesticide exposure model. Based on use data, 10 crops account for 81% of the total risk. We detected 49 pesticide compounds in bee-collected pollen. Although herbicides and fungicides constitute the bulk of detected pesticides, both in frequency and amount quantified, unsurprisingly, insecticides contribute the most to risk. Landscape composition and configuration metrics did not predict observed pesticide risk, and interactions with bee species indicate taxa-dependency in predictions. Landscape load predicted observed risk consistently between taxa. Risk estimates from our exposure model were strongly predictive but only when considering realized risk (i.e., risk estimates based on prior pesticide use information). Synthesis and applications. Predicting pesticide risk based on landscape patterns could enable landscape-scale ERA. However, simple metrics of landscape pattern, such as proportion of agricultural land, are not sufficient. We found that risk observed in bee-collected pollen was best predicted when integrating spatialized pesticide use in the pesticide exposure model, underscoring the importance of such data for research, monitoring and mitigation. Further, we propose a guidance framework for future landscape ecotoxicological risk analyses that clarifies data needs relative to risk prediction goals.
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| 5. |
- Olsson, Ola, et al.
(författare)
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Modeling pollinating bee visitation rates in heterogeneous landscapes from foraging theory
- 2015
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800. ; 316, s. 133-143
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Tidskriftsartikel (refereegranskat)abstract
- Pollination by bees is important for food production. Recent concerns about the declines of both domestic and wild bees, calls for measures to promote wild pollinator populations in farmland. However, to be able to efficiently promote and prioritize between measures that benefit pollinators, such as modified land use, agri-environment schemes, or specific conservation measures, it is important to have a tool that accurately predicts how bees use landscapes and respond to such measures. In this paper we compare an existing model for predicting pollination (the “Lonsdorf model”), with an extension of a general model for habitat use of central place foragers (the “CPF model”). The Lonsdorf model has been shown to perform relatively well in simple landscapes, but not in complex landscapes. We hypothesized that this was because it lacks a behavioral component, assuming instead that bees in essence diffuse out from the nest into the landscape. By adding a behavioral component, the CPF model in contrast assumes that bees only use those parts of the landscape that enhances their fitness, completely avoiding foraging in other parts of the landscape. Because foraging is directed towards the most rewarding foraging habitat patches as determined by quality and distance, foraging habitat will include a wide range of forage qualities close to the nest, but a much narrower range farther away. We generate predictions for both simple and complex hypothetical landscapes, to illustrate the effect of including the behavioral rule, and for real landscapes. In the real landscapes the models give similar predictions for visitation rates in simple landscapes, but more different predictions in heterogeneous landscapes. We also analyze the consequences of introducing hedgerows near a mass-flowering crop field under each model. The Lonsdorf model predicts that any habitat improvement will enhance pollination of the crop. In contrast, the CPF model predicts that the hedgerow must provide good nesting sites, and not just foraging opportunities, for it to benefit pollination of the crop, because good forage quality alone may drain bees away from the field. Our model can be used to optimize pollinator mitigation measures in real landscapes.
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| 6. |
- Sponsler, Douglas B., et al.
(författare)
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Pesticides and pollinators : A socioecological synthesis
- 2019
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 662, s. 1012-1027
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Forskningsöversikt (refereegranskat)abstract
- The relationship between pesticides and pollinators, while attracting no shortage of attention from scientists, regulators, and the public, has proven resistant to scientific synthesis and fractious in matters of policy and public opinion. This is in part because the issue has been approached in a compartmentalized and intradisciplinary way, such that evaluations of organismal pesticide effects remain largely disjoint from their upstream drivers and downstream consequences. Here, we present a socioecological framework designed to synthesize the pesticide-pollinator system and inform future scholarship and action. Our framework consists of three interlocking domains-pesticide use, pesticide exposure, and pesticide effects–each consisting of causally linked patterns, processes, and states. We elaborate each of these domains and their linkages, reviewing relevant literature and providing empirical case studies. We then propose guidelines for future pesticide-pollinator scholarship and action agenda aimed at strengthening knowledge in neglected domains and integrating knowledge across domains to provide decision support for stakeholders and policymakers. Specifically, we emphasize (1) stakeholder engagement, (2) mechanistic study of pesticide exposure, (3) understanding the propagation of pesticide effects across levels of organization, and (4) full-cost accounting of the externalities of pesticide use and regulation. Addressing these items will require transdisciplinary collaborations within and beyond the scientific community, including the expertise of farmers, agrochemical developers, and policymakers in an extended peer community.
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