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- Birkhofer, Klaus, et al.
(författare)
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Methods to identify the prey of invertebrate predators in terrestrial field studies
- 2017
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 7:6, s. 1942-1953
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Tidskriftsartikel (refereegranskat)abstract
- Predation is an interaction during which an organism kills and feeds on another organism. Past and current interest in studying predation in terrestrial habitats has yielded a number of methods to assess invertebrate predation events in terrestrial ecosystems. We provide a decision tree to select appropriate methods for individual studies. For each method, we then present a short introduction, key examples for applications, advantages and disadvantages, and an outlook to future refinements. Video and, to a lesser extent, live observations are recommended in studies that address behavioral aspects of predator-prey interactions or focus on per capita predation rates. Cage studies are only appropriate for small predator species, but often suffer from a bias via cage effects. The use of prey baits or analyses of prey remains are cheaper than other methods and have the potential to provide per capita predation estimates. These advantages often come at the cost of low taxonomic specificity. Molecular methods provide reliable estimates at a fine level of taxonomic resolution and are free of observer bias for predator species of any size. However, the current PCR-based methods lack the ability to estimate predation rates for individual predators and are more expensive than other methods. Molecular and stable isotope analyses are best suited to address systems that include a range of predator and prey species. Our review of methods strongly suggests that while in many cases individual methods are sufficient to study specific questions, combinations of methods hold a high potential to provide more holistic insights into predation events. This review presents an overview of methods to researchers that are new to the field or to particular aspects of predation ecology and provides recommendations toward the subset of suitable methods to identify the prey of invertebrate predators in terrestrial field research.
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| 2. |
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| 3. |
- Roubinet, Eve, et al.
(författare)
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Diet of generalist predators reflects effects of cropping period and farming system on extra- and intraguild prey
- 2017
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Ingår i: Ecological Applications. - : Wiley. - 1051-0761 .- 1939-5582. ; 27:4, s. 1167-1177
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Tidskriftsartikel (refereegranskat)abstract
- The suppression of agricultural pests by natural enemies, including generalist arthropod predators, is an economically important regulating ecosystem service. Besides pests, generalist predators may also consume non-pest extraguild and intraguild prey, which can affect their impact on pest populations. This may either reduce the impact of generalist predators on pest populations, because they are diverted from pest predation, or increase it, as it helps them survive periods of low pest availability. However, the availability of pest prey and alternative, non-pest prey can vary over the crop growing season and between farming systems, potentially affecting predator-prey interactions and the levels of biological control. We have limited information about how farming systems and environmental variation over the crop growing season influence predator diets. This limits our ability to predict the importance of generalist predators as natural enemies of agricultural pests. Here we utilize molecular gut content analyses to assess detection frequencies of extra- and intraguild prey DNA in generalist predator communities in replicated organically and conventionally managed cereal fields at two key periods of the cropping season for aphid biological control. This is done in order to understand how farming system, crop season, prey availability and predator community composition determine the composition of predator diets. Aphid pests and decomposers (springtails) were equally important prey for generalist predators early in the growing season. Later in the season, the importance of aphid prey increased with increasing aphid densities while springtail predation rates were positively correlated to abundance of this prey at both early and late crop growth stages. Intraguild predation was unidirectional: carabids fed on spiders, whereas spiders rarely fed on carabids. Carabids had higher detection frequencies for the two most common spider families in organically compared to conventionally managed fields. Our study documents that predation by generalist predator communities on aphid pests increases with pest numbers independently of their generally widespread consumption of alternative, non-pest prey. Therefore, conservation strategies in agricultural fields could promote biological control services by promoting high levels of alternative non-pest prey for generalist predator communities.
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| 4. |
- Roubinet, Eve
(författare)
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Food webs in agroecosystems : implications for biological control of insect pests
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The management of insect pests in modern agriculture is dominated by chemical control, despite wide recognition of its detrimental impact on the environment and human health. As a sustainable alternative, the service of biological control of insect pests is provided by a diversity of natural enemies, such as ground dwelling carabids and spiders. A better understanding of natural enemy communities and the feeding relationship between natural enemies and their prey is therefore crucial to better conserve and promote the provisioning of biological control in agricultural fields. To this end, we quantitatively summarized published studies that addressed the relationship between increased natural enemy diversity and biological control and studied moderation by biotic and abiotic factors. The results of this meta-analysis support an overall positive effect of increased natural enemy diversity on herbivore suppression, and suggest this effect is lessened by an increase of prey diversity. I then focused on communities of generalist, ground dwelling predators controlling aphids in cereal fields. I used recently developed DNA based molecular gut content analysis to study the feeding relationships between predators and their prey, i.e., food webs, and their implications for biological control. I investigated the effects and underlying mechanisms of increased predator diversity on aphid biological control in manipulative field cage experiments, and identified feeding interactions in relation to the availability of predators and prey during the growing season in field conditions. I showed that generalist predators appear to be functionally redundant in the provisioning of cereal aphid biological control, when considering short time periods. However, when the entire cropping season is considered the importance of different predators as aphid biological control agents varied, which suggests that high predator diversity may provide a more stable biological control service over time. The findings of this thesis support the design of conservation strategies that promote predator diversity and high levels of non-pest extraguild prey in order to sustain generalist ground dwelling predators and secure their contribution to biological control services in agricultural fields.
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| 5. |
- Roubinet, Eve, et al.
(författare)
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High Redundancy as well as Complementary Prey Choice Characterize Generalist Predator Food Webs in Agroecosystems
- 2018
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Food web structure influences ecosystem functioning and the strength and stability of associated ecosystem services. With their broad diet, generalist predators represent key nodes in the structure of many food webs and they contribute substantially to ecosystem services such as biological pest control. However, until recently it has been difficult to empirically assess food web structure with generalist predators. We utilized DNA-based molecular gut-content analyses to assess the prey use of a set of generalist invertebrate predator species common in temperate agricultural fields. We investigated the degree of specialization of predator-prey food webs at two key stages of the cropping season and analysed the link temperature of different trophic links, to identify non-random predation. We found a low level of specialization in our food webs, and identified warm and cool links which may result from active prey choice or avoidance. We also found a within-season variation in interaction strength between predators and aphid pests which differed among predator species. Our results show a high time-specific functional redundancy of the predator community, but also suggest temporally complementary prey choice due to within-season succession of some predator species.
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| 6. |
- Roubinet, Eve
(författare)
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Hur påverkar skalbaggarnas och spindlarnas matvanor den biologiska bekämpningen?
- 2016
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Ingår i: Växtskyddsnotiser. - 2000-8465. ; 70, s. 4-6
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- åkrar producerar inte bara livsmedel, de är också boplatser för många växter och djur som kan förse oss med viktiga ekosystemtjänster. Ett exempel på detta är de naturliga fienderna, det vill säga de nyttoinsekter som kan bidra till en effektiv skadedjursbekämpning (så kallad biologisk bekämpning). Skalbaggar och spindlar är exempelvis naturliga fiender till många skadedjur i jordbruket, såsom bladlöss i vårkorn. Dessa naturliga fiender, eller predatorer som de också kallas, är generalister. Detta innebär att de inte bara äter skadedjur, utan också äter många andra djur i åkermarkerna. Men kan de fortfarande ge en effektiv biologisk bekämpning om de äter andra bytesdjur, även dem som inte är skadedjur? Utöver detta så är intensifieringen av jordbruket - särskilt vad gäller användningen av kemiska bekämpningsmedel - ett hot mot naturliga fienders mångfald och mängd i åkrar. Men vad behövs egentligen mångfalden för?
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| 7. |
- Roubinet, Eve
(författare)
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Management of the broad bean weevil (Bruchus rufimanus Boh.) in faba bean (Vicia faba L.)
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Summary Bruchus rufimanus Boh. is a common pest on faba beans (Vicia faba L.) all over Europe and worldwide. The area of faba bean production is increasing in Sweden and in Europe, partly encouraged by the CAP subsidies for legume crops and diversified crop rotations. At the same time, number of the insecticides commonly used against B. rufimanus have been removed from the market as pollinators risk to be harmed as the treatment timing corresponds to crop flowering. In Sweden, only one insecticide is available and its efficacy against B. rufimanus is not well established. The pest pressure is likely to increase if no measures are taken to reduce the population. This has increased the interest in alternative management methods in Europe, particularly so in the UK and in France where faba beans is extensively grown. This report presents an overview of B. rufimanus biology and management strategies. This report is the result of a literature search including scientific literature and other available documentations (e.g., grower organizations, technical institutes). Additionally, contacts with technicians, referring advisors and researchers across Europe involved in research projects related to B. rufimanus management, enabled me to obtain an up-to-date overview of the advancement of their projects that I present in this report. In conclusion I suggest further investigations that would clarify the risks for faba bean production and help identify measures both in term of field management and direct control that could be recommended in Sweden.
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