Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    No evidence of modulation of indirect plant resistance of Brassica rapa plants by volatiles from soil-borne fungi
    Moisan, Kay ; Lucas-Barbosa, Dani ; Villela, Alexandre ; Greenberg, Liana O. ; Cordovez, Viviane ; Raaijmakers, Jos M. ; Dicke, Marcel - \ 2020
    Ecological Entomology 45 (2020)5. - ISSN 0307-6946 - p. 1200 - 1211.
    HIPVs - parasitoids - predators - recruitment

    Upon herbivory, plants emit specific herbivore-induced plant volatiles (HIPVs) that can attract natural enemies of the herbivore thus serving as indirect plant resistance. Not only insect herbivores, but microorganisms may also affect HIPV emission before or after plant colonisation, which in turn can affect behaviour of natural enemies of the herbivore. Yet, it remains elusive whether volatiles from microorganisms influence HIPV emission and indirect plant resistance. In this study, we investigated whether exposure of Brassica rapa roots to volatiles from soil-borne fungi influence HIPV emission and the recruitment of natural enemies of Pieris brassicae larvae. Using a two-compartment pot system, we performed greenhouse and common-garden experiments, and we profiled plant HIPV emission. We found that exposure of plant roots to fungal volatiles did not affect the number of P. brassicae larvae recollected from the plants, suggesting a neutral effect of the fungal volatiles on natural predation. Likewise, in a greenhouse, similar numbers of larvae were parasitised by Cotesia glomerata wasps on control plants as on fungal volatile-exposed plants. Additionally, chemical analysis of HIPV profiles revealed no qualitative and quantitative differences between control plants and fungal volatile-exposed plants that were both infested with P. brassicae larvae. Together, our data indicate that root exposure to fungal volatiles did not affect indirect plant resistance to an insect herbivore. These findings provide new insight into the influence of indirect plant resistance by fungal volatiles that are discussed together with the effects of fungal volatiles on direct plant resistance.

    Next generation biological control – an introduction
    Hesran, Sophie Le; Ras, Erica ; Wajnberg, Eric ; Beukeboom, Leo W. - \ 2019
    Entomologia Experimentalis et Applicata 167 (2019)7. - ISSN 0013-8703 - p. 579 - 583.
    antagonistic micro-organisms - artificial selection - biocontrol - efficacy improvement - experimental evolution - genetic variation - induced plant resistance - molecular tools - natural enemies - parasitoids - pathogens - predators
    Trophic Regulations of the Soil Microbiome
    Thakur, Madhav P. ; Geisen, Stefan - \ 2019
    Trends in Microbiology 27 (2019)9. - ISSN 0966-842X - p. 771 - 780.
    bacteria - climate change - food webs - fungi - predators - top-down control

    The soil microbiome regulates vital ecosystem functions ranging from primary production to soil carbon sequestration. Yet, we have only begun to understand the factors regulating the soil microbiome. While the importance of abiotic factors is increasingly recognized, the roles of trophic regulations in driving the structure and function of the soil microbiome remain less explored. Here, we review the current understanding of how and when microbial and top predators of the soil shape the community structure and function of the soil microbiome via both direct and indirect effects. We finally highlight that the structure and function of the soil microbiome depend on the interactive effects among predation, plant inputs, and abiotic variables present in the soil.

    Data from: Cascading effects of predator activity on tick-borne disease risk
    Hofmeester, T.R. ; Jansen, P.A. ; Wijnen, H.J. ; Coipan, E.C. ; Fonville, Manoj ; Prins, H.H.T. ; Sprong, Hein ; Wieren, S.E. van - \ 2017
    Wageningen University & Research
    Borrelia burgdorferi - predators - carnivores - rodents
    Predators and competitors of vertebrates can in theory reduce the density of infected nymphs (DIN)—an often-used measure of tick-borne disease risk—by lowering the density of reservoir-competent hosts and/or the tick burden on reservoir-competent hosts. We investigated this possible indirect effect of predators by comparing data from 20 forest plots across the Netherlands that varied in predator abundance. In each plot, we measured the density of questing Ixodes ricinus nymphs (DON), DIN for three pathogens, rodent density, the tick burden on rodents and the activity of mammalian predators. We analysed whether rodent density and tick burden on rodents were correlated with predator activity, and how rodent density and tick burden predicted DON and DIN for the three pathogens. We found that larval burden on two rodent species decreased with activity of two predator species, while DON and DIN for all three pathogens increased with larval burden on rodents, as predicted. Path analyses supported an indirect negative correlation of activity of both predator species with DON and DIN. Our results suggest that predators can indeed lower the number of ticks feeding on reservoir-competent hosts, which implies that changes in predator abundance may have cascading effects on tick-borne disease risk.
    Biologische bestrijding van wol- en schildluis in de sierteelt onder glas
    Kruidhof, H.M. ; Messelink, G.J. ; Leman, A. ; Vijverberg, Roland - \ 2016
    Wageningen : Wageningen UR Glastuinbouw - 1
    tuinbouw - glastuinbouw - biologische bestrijding - sierteelt - cymbidium - rosaceae - planococcus citri - coccoidea - sluipwespen - predatoren - roofinsecten - thrips - coleoptera - horticulture - greenhouse horticulture - biological control - ornamental horticulture - cymbidium - rosaceae - planococcus citri - coccoidea - parasitoid wasps - predators - predatory insects - thrips - coleoptera
    Het doel van dit project is om de biologische bestrijding van wol-en schildluis te verbeteren met nieuwe inzetstrategieën van bestaande bestrijders en door opsporing van complementaire nieuwe bestrijders. Poster van het PlantgezondheidEvent 2016.
    Eat and be eaten: porpoise diet studies
    Leopold, M.F. - \ 2015
    Wageningen University. Promotor(en): Peter Reijnders. - Wageningen : Wageningen University - ISBN 9789462575585 - 239
    phocoenidae - phocoena - diervoedering - voedingsgedrag - predatoren - voedingsgewoonten - foerageren - zeehonden - noordzee - nederland - phocoenidae - phocoena - animal feeding - feeding behaviour - predators - feeding habits - foraging - seals - north sea - netherlands
    Early-season movement dynamics of phytophagous pest and natural enemies across a native vegetation-crop ecotone
    Macfadyen, S. ; Hopkinson, J. ; Parry, H. ; Neave, M.J. ; Bianchi, F.J.J.A. ; Zalucki, M.P. ; Schellhorn, N.A. - \ 2015
    Agriculture, Ecosystems and Environment 200 (2015). - ISSN 0167-8809 - p. 110 - 118.
    managing ecosystem services - agricultural landscape - biological-control - spatial scales - dispersal - colonization - predators - ecology - parasitoids - suppression
    There is limited understanding about how insect movement patterns are influenced by landscape features, and how landscapes can be managed to suppress pest phytophage populations in crops. Theory suggests that the relative timing of pest and natural enemy arrival in crops may influence pest suppression. However, there is a lack of data to substantiate this claim. We investigate the movement patterns of insects from native vegetation (NV) and discuss the implications of these patterns for pest control services. Using bi-directional interception traps we quantified the number of insects crossing an NV/crop ecotone relative to a control crop/crop interface in two agricultural regions early in the growing season. We used these data to infer patterns of movement and net flux. At the community-level, insect movement patterns were influenced by ecotone in two out of three years by region combinations. At the functional-group level, pests and parasitoids showed similar movement patterns from NV very soon after crop emergence. However, movement across the control interface increased towards the end of the early-season sampling period. Predators consistently moved more often from NV into crops than vice versa, even after crop emergence. Not all species showed a significant response to ecotone, however when a response was detected, these species showed similar patterns between the two regions. Our results highlight the importance of NV for the recruitment of natural enemies for early season crop immigration that may be potentially important for pest suppression. However, NV was also associated with crop immigration by some pest species. Hence, NV offers both opportunities and risks for pest management. The development of targeted NV management may reduce the risk of crop immigration by pests, but not of natural enemies.
    Graded behavioral responses and habituation to sound in the common cuttlefish, Sepia officinalis
    Samson, J.E. ; Mooney, T.A. ; Gussekloo, S.W.S. ; Hanlon, R.T. - \ 2014
    Journal of Experimental Biology 217 (2014)24. - ISSN 0022-0949 - p. 4347 - 4355.
    equal-loudness contours - acoustic startle - water movements - squid - cephalopods - fish - predators - sensitization - lolliguncula - sensitivity
    Sound is a widely available and vital cue in aquatic environments yet most bioacoustic research has focused on marine vertebrates, leaving sound detection in invertebrates poorly understood. Cephalopods are an ecologically key taxon that likely use sound and may be impacted by increasing anthropogenic ocean noise, but little is known regarding their behavioral responses or adaptations to sound stimuli. These experiments identify the acoustic range and levels that elicit a wide range of secondary defense behaviors such as inking, jetting, and rapid coloration change. Secondarily, it was found that cuttlefish habituate to certain sound stimuli. The present study examined the behavioral responses of 22 cuttlefish (Sepia officinalis) to pure-tone pips ranging from 80-1000 Hz with sound pressure levels of 85–188 dB re 1 µPa rms and particle accelerations of 0-17.1 m.s-2. Cuttlefish escape responses (inking, jetting) were observed between frequencies of 80-300 Hz and at sound levels above 140 dB re 1 µPa rms and 0.01 m.s-2 (0.74 m.s-2 for inking responses). Body patterning changes and fin movements were observed at all frequencies and sound levels. Response intensity was dependent upon stimulus amplitude and frequency, suggesting that cuttlefish also possess loudness perception with a maximum sensitivity around 150 Hz. Cuttlefish habituated to repeated 200 Hz tone pips, at two sound intensities. Total response inhibition was not reached, however, and a basal response remained present in most animals. The graded responses provide a loudness sensitivity curve and suggest an ecological function for sound-use in cephalopods.
    Effect of light quality on movement of Pterostichus melanarius (Coleoptera: Carabidae)
    Allema, A.B. - \ 2014
    insects - movement activity - movement behavior - movement speed - red light sensitivity - resting behavior - arable land - insect pests - natural enemies - predatory insects - predators - pterostichus melanarius - dispersal - movement - animal behavior - quantitative analysis - motility - modeling - methodology
    The aim of this project was to study the effect of red light on night time behaviour of Pterostichus melanarius (Coleoptera: Carabidae). An experiment was conducted in experimental arenas in the autumn of 2008. Beetles were recorded 20 min per hour during a period of 8 hours under red light, near infrared radiation and white light.
    Effects of founder population size on the performance of Orius laevigatus (Hemiptera: Anthocoridae) colonies
    Castañe, C. ; Bueno, V.H.P. ; Carvalho, L.M. ; Lenteren, J.C. van - \ 2014
    Biological Control 69 (2014). - ISSN 1049-9644 - p. 107 - 112.
    biological-control agents - predators - tephritidae - selection - diptera
    Orius laevigatus (Hemiptera: Anthocoridae) is a key predator of thrips and is mass reared in large numbers for use in biological control. The aim of this study was to evaluate the effect of founder population size on the biological and behavioral performance of O. laevigatus over time. Laboratory lines were started from 1, 10 and 50 founder couples from 750 adults collected in the field and their performance was evaluated at the 5th–6th and 10th–11th generations. Adaptation to the captive rearing situation occurred in the 10 and 50 founder couples lines while it failed in the 1 founder couple line. The intrinsic rate of natural increase (rm) increased and the period for doubling the population (D) decreased over the generations in the 10 and 50 founder couples lines, while (rm) decreased and (D) increase in the 1 founder couple line. Also, consumption of Frankliniella occidentalis prey was significantly lower for females from the 1 founder couple line at the 5th generation compared to females from the 10 and 50 founder couples lines. Females of laboratory lines of all founder couples did not respond to odours from thrips infested plants during the 5th and 10th generations, whereas wild females strongly reacted to these odours. We suggest that the lack of reaction to infested plant volatiles may be due to the artificial rearing method where mass reared predators do not experience an infested crop. The results showed that the 1 founder couple line differed from the 10 and 50 founder couples lines, suggesting that bottlenecking had an effect at that level. However, no difference was found between the 10 and 50 founder couples lines which suggest that these founder numbers can be used to start laboratory-reared O. laevigatus lines without a significant loss in quality of its relevant biological characteristics.
    Quantifying and simulating movement of the predator carabid beetle Pterostichus melanarius in arable land
    Allema, A.B. - \ 2014
    Wageningen University. Promotor(en): Joop van Lenteren, co-promotor(en): Walter Rossing; Wopke van der Werf. - Wageningen : Wageningen University - ISBN 9789461739100 - 133
    bouwland - insectenplagen - natuurlijke vijanden - roofinsecten - predatoren - pterostichus melanarius - verspreiding - beweging - diergedrag - kwantitatieve analyse - motiliteit - modelleren - methodologie - arable land - insect pests - natural enemies - predatory insects - predators - pterostichus melanarius - dispersal - movement - animal behaviour - quantitative analysis - motility - modeling - methodology

    Keywords: landscape entomology, movement ecology, quantifying movement, population spread, habitat heterogeneity, motility, edge-behaviour, diffusion model, model selection, inverse modelling, Pterostichus melanarius, Carabidae, entomophagous arthropod

    Biological control provided by entomophagous arthropods is an ecosystem service with the potential to reduce pesticide use in agriculture. The distribution of entomophagous arthropods and the associated ecosystem service over crop fields is affected by their dispersal capacity and landscape heterogeneity. Current knowledge on entomophagous arthropod distribution and movement patterns, in particular for soil dwelling predators, is insufficient to provide advice on how a production landscape should be re-arranged to maximally benefit from biological pest control. Movement has mainly been measured in single habitats rather than in habitat mosaics and as a consequence little information is available on behaviour at habitat interfaces, i.e. the border between two habitats.

    This study contributes to insight into movement patterns of the entomophagous arthropod Pterostichus melanarius (Illiger) in an agricultural landscape as a knowledge basis for redesign of landscapes for natural pest control. Movement patterns were studied with video equipment in experimental arenas of 5 m2 and with mark-recapture at much larger scales in the field. Interpretation of the results was supported by diffusion models that accounted for habitat specific motility µ (L2 T−1), a measure for diffusion of a population in space and time, and preference behaviour at habitat interfaces.

    Movement of carabids has mostly been quantified as movement rate, which cannot be used for scaling-up. Available information on movement rate of carabids was made available for scaling-up by calculating motility from published data and looking for patterns through meta-analysis of data from thirteen studies, including 55 records on twelve species. Beetles had on average a three times higher motility in arable land than in forest/hedgerow habitat. The meta-analysis did not identify consistent differences in motility at the individual species level, and a grouping of species according to gender or size did not demonstrate a significant gender or size effect.

    A methodology to directly estimate motility from data using inverse modelling was evaluated on data of a mass mark-recapture field experiment in a single field of winter triticale (x Triticosecale Wittmack.). Inverse modelling yielded the same result as motility calculated from squared displacement distances. In the first case, motility was calculated as an average over motility of individuals, in the second case motility was estimated from a population density distribution fitted to the recapture data. The similarity in motility between these two very different approaches strengthens the confidence in motility as a suitable concept for quantifying dispersal rate of carabid beetles, and in inverse modelling as a method to retrieve movement parameters from observed patterns.

    The effect of habitat heterogeneity on movement behaviour was studied for P. melanarius across adjacent fields of oilseed radish (Raphanus sativus) and rye (Secale cereale) in a mark-recapture experiment. The field study was complemented by observations on movement behaviour in the experimental arena. Motility was neither significantly different between the crop species in the field nor in the arena. Overall movement in the field was significantly affected by behaviour at the interface between the crops. Beetles moved more frequently from rye to oilseed radish than in the opposite direction. The arena data indicated greater frequency of habitat entry into oilseed radish as compared to rye. Analysis of video tracking data from the arena resulted in estimates of motility that, when scaled up were close to those obtained in the field. Thus, the studies at the smaller and larger scales gave qualitatively and quantitatively similar results.

    The effect of habitat heterogeneity on within-season dispersal behaviour was further explored in an agricultural landscape mosaic comprising perennial strips and different crop species with distinct tillage management. Semi-natural grass margins were functionally different from the crop habitats. Motility was lower in margins than in crop habitats, and at the crop-margin interface more beetles moved towards the crop than to the margin. Margins thus effectively acted as barriers for dispersal. In the crop habitats motility differed between fields but no consistent relations were found with crop type, food availability or tillage. Based on the motility in crop habitats P. melanarius was predicted to disperse over a distance of about 100 – 160 m during a growing season in a landscape without semi-natural elements. Given this range little redistribution of beetles is expected between fields within a growing season, even more when fields are surrounded by grass margins or hedgerows, meaning that the success of biological control by this species is more dependent on field management affecting local population dynamics than on habitat heterogeneity.

    This thesis has resulted in a methodological approach to quantify dispersal behaviour of ground-dwelling insects from mark-recapture data in heterogeneous environments using inverse modelling. The combination of models and data proved to be powerful for studying movement and contributes to the development of predictive dynamic models for population spread of entomophagous arthropods. These models for population spread may be used as part of multi-objective assessment of alternative landscape configurations to find spatial arrangements of land use that maximize the ecosystem service of biological control as part of a wider set of landscape functions.

    Verbetering inzet Macrolophus pygmaeus in tomaat
    Holstein, R. van; Messelink, G.J. - \ 2014
    Bleiswijk : Wageningen UR Glastuinbouw (Rapport / Wageningen UR Glastuinbouw 1293) - 20
    organismen ingezet bij biologische bestrijding - hemiptera - macrolophus caliginosus - tomaten - solanum lycopersicum - gewasbescherming - bestrijdingsmethoden - plaagbestrijding met natuurlijke vijanden - predatoren - biological control agents - hemiptera - macrolophus caliginosus - tomatoes - solanum lycopersicum - plant protection - control methods - augmentation - predators
    De vestiging van de roofwants Macrolophus pygmaeus in tomaat komt vaak moeizaam op gang in de periode wintervoorjaar. Op een commercieel tomatenbedrijf is gekeken of de populatiegroei van Macrolophus versneld kan worden met alternatief voedsel. Een standaard toepassing van Ephestia-eieren (35g/ha) werd vergeleken met een 5x zo hoge dosering van de veel goedkopere Artemiacysten (175g/ha). Het wekelijks verblazen van dit voedsel verdrievoudigde de populatie Macrolophus ten opzichte van de behandeling met Ephestia-eieren. De dichtheden liepen op tot meer dan 100 per plant in een periode van 16 weken. Het viel daarbij op dat Macrolophus nauwelijks aanwezig was in de paden waar geen voedsel was toegediend. Het is dus zaak om verder te kijken hoe dit voedsel het beste kan worden toegediend om tot een optimale verdeling van Macrolophus te komen. Dit onderzoek laat in ieder geval zien dat de populatieopbouw van Macrolophus in een tomatengewas verder versneld kan worden door het aanbieden van alternatief voedsel. Ephestia-eieren zijn daarvoor het meest geschikt, maar de goedkopere Artemiacysten kunnen een goede aanvulling of een goed alternatief zijn. The establishment of Macrolophus pygmaeus in a tomato crop is often poor during winter and spring when prey densities are low. In this study we evaluated the effects of foods prays on the population dynamics of Macrolophus. Weekly applications of Ephestia eggs were compared with a 5 times higher dose of Artemia cysts, which is a much cheaper food source. This food source resulted in 3 times higher predator densities compared to the Ephestia treatment. The densities increased to more than 100 per plant in a period of 16 weeks. The predatory bugs remarkebly aggregated on the plants with food and were hardly present in the rows where no food was applied. It is therefore important to develop methods that optimize the distribution of Macrolophus in a crop.
    How superdiffusion gets arrested: ecological encounters explain shift from Lévy to Brownian movement
    Jager, M. de; Bartumeus, F. ; Kölzsch, A. ; Weissing, F.J. ; Hengeveld, G.M. ; Nolet, B.A. ; Herman, P.M.J. ; Koppel, J. van de - \ 2014
    Proceedings of the Royal Society. B: Biological Sciences 281 (2014)1774. - ISSN 0962-8452 - 8 p.
    power-law distributions - flight search patterns - environmental complexity - walks evolve - predators - dynamics - animals - mussels - success
    Ecological theory uses Brownian motion as a default template for describing ecological movement, despite limited mechanistic underpinning. The generality of Brownian motion has recently been challenged by empirical studies that highlight alternative movement patterns of animals, especially when foraging in resource-poor environments. Yet, empirical studies reveal animals moving in a Brownian fashion when resources are abundant. We demonstrate that Einstein's original theory of collision-induced Brownian motion in physics provides a parsimonious, mechanistic explanation for these observations. Here, Brownian motion results from frequent encounters between organisms in dense environments. In density-controlled experiments, movement patterns of mussels shifted from Lévy towards Brownian motion with increasing density. When the analysis was restricted to moves not truncated by encounters, this shift did not occur. Using a theoretical argument, we explain that any movement pattern approximates Brownian motion at high-resource densities, provided that movement is interrupted upon encounters. Hence, the observed shift to Brownian motion does not indicate a density-dependent change in movement strategy but rather results from frequent collisions. Our results emphasize the need for a more mechanistic use of Brownian motion in ecology, highlighting that especially in rich environments, Brownian motion emerges from ecological interactions, rather than being a default movement pattern
    Interactions between conventional and organic farming for biocontrol services across the landscape
    Bianchi, F.J.J.A. ; Ives, A.R. ; Schellhorn, N.A. - \ 2013
    Ecological Applications 23 (2013). - ISSN 1051-0761 - p. 1531 - 1543.
    generalist natural enemies - pest-control - biological-control - soybean aphid - pea aphid - biodiversity - populations - management - predators - insecticides
    While the area of organic crop production increases at a global scale, the potential interactions between pest management in organic and conventionally managed systems have so far received little attention. Here, we evaluate the landscape-level co-dependence of insecticide-based and natural enemy-based pest management using a simulation model for parasitoid–host interactions in landscapes consisting of conventionally and organically managed fields. In our simulations conventional management consists of broad-spectrum or selective insecticide application, while organic management involves no insecticides. Simulations indicate that insecticide use can easily result in lose–lose scenarios whereby both organically and conventionally managed fields suffer from increased pest loads as compared to a scenario where no insecticides are used, but that under some conditions insecticide use can be compatible with biocontrol. Simulations also suggest that the pathway to achieve the insecticide reduction without triggering additional pest pressure is not straightforward, because increasing the proportion of organically managed fields or reducing the spray frequency in conventional fields can potentially give rise to dramatic increases in pest load. The disruptive effect of insecticide use, however, can be mitigated by spatially clustering organic fields and using selective insecticides, although the effectiveness of this mitigation depends on the behavioral traits of the biocontrol agents. Poorly dispersing parasitoids and parasitoids with high attack rates required a lower amount of organically managed fields for effective pest suppression. Our findings show that the transition from a landscape dominated by conventionally managed crops to organic management has potential pitfalls; intermediate levels of organic management may lead to higher pest burdens than either low or high adoption of organic management.
    Multitrophic interactions on a range-expanding plant species
    Fortuna, T.F.M. - \ 2013
    Wageningen University. Promotor(en): Louise Vet; J.A. Harvey. - Wageningen : Wageningen UR - ISBN 9789461737656 - 229
    planten - invasieve soorten - geïntroduceerde soorten - herbivoren - ongewervelde dieren - natuurlijke vijanden - predatoren - parasitoïden - multitrofe interacties - bunias orientalis - verdedigingsmechanismen - plants - invasive species - introduced species - herbivores - invertebrates - natural enemies - predators - parasitoids - multitrophic interactions - bunias orientalis - defence mechanisms

    Studies on the ecological impacts of exotic invasive plants have mainly focused on inter-continental invasions. However due to global environmental changes, a rapid increase in intra-continental range-expanding plants has been observed. In this context, multitrophic interactions between exotic plants, native herbivores and their natural enemies have been largely ignored. This thesis aimed at examining how an exotic range-expanding plant interacts with aboveground insect herbivores and their natural enemies and how it can contribute to the successful establishment of the exotic plant. In addition, it examines how resistance traits of different populations of the range-expander affect the behaviour and performance of herbivores and their natural enemies in the new habitat. Bunias orientalis (Capparales: Brassicaceae) is perennial plant from extreme south-eastern Europe and Asia that has recently expanded its range and become invasive in northern and central parts of Europe. In the Netherlands, it is considered naturalized but non-invasive.

    Firstly, using a community approach, I found that Bu. orientalis suffered less herbivore damage and harboured smaller invertebrate communities than sympatric native Brassicaceae in the Netherlands. The exotic plant has been found of low quality for the larval growth of the specialist herbivore (Pieris brassicae). Furthermore, two of its gregarious parasitoids were differentially affected by the quality of the exotic plant. The pupal parasitoid (Pteromalus puparum) survived better than the larval parasitoid (Cotesia glomerata), and the latter parasitized less hosts on the exotic than on native plants. Therefore, the herbivore can be selected to adapt to the new plant by conferring an enemy free space to the herbivore. In this case, a plant shift by the specialist herbivore might occur and thus preventing the further spread of the exotic plant. Conversely, in the field I found greater carnivore pressure on Bu. orientalis compared to other native Brassicaceae, particularly in the peak of arthropod abundance. Hence, top-down forces exerted by herbivore natural enemies may act in concert with bottom-up control of plant resistance traits to counteract herbivore plant shift and promote the successful range expansion of the exotic plant.

    Secondly, using a biogeographical approach, I found a considerable intraspecific variation in defence traits (trichomes, glucosinolates, metabolic fingerprints) of Bu. orientalis populations from the native and the exotic range. Plants collected in the native range were better defended than their exotic conspecifics. This variation matched with the performance of a generalist herbivore (Mamestra brassicae) and its parasitoid (Microplitis mediator), which developed poorly in plants from the native range. The results suggest that the defensive mechanisms of Bu. orientalis might have been counter-selected during the range expansion of the exotic plant. Further studies, however, need to examine if enemy release in the new range is followed by an increase in performance of the exotic plant. Finally, a comparative study of multitrophic interactions, both above- and belowground, in the plant native range and along the transect of its range expansion can help to clarify the mechanisms underlying the invasive success of Bu. orientalis.

    Banker plant systeem voor Delphastus catalinae tegen wittevlieg
    Linden, A. van der - \ 2013
    Bleiswijk : Wageningen UR Glastuinbouw (Rapporten WUR GTB 1266) - 18
    sierteelt - plagenbestrijding - trialeurodes vaporariorum - biologische bestrijding - encarsia formosa - coccinellidae - glastuinbouw - organismen ingezet bij biologische bestrijding - predatoren - ornamental horticulture - pest control - trialeurodes vaporariorum - biological control - encarsia formosa - coccinellidae - greenhouse horticulture - biological control agents - predators
    Kaswittevlieg Trialeurodes vaporariorum is voor verscheidene sierteeltgewassen een belangrijke plaag. Naast de inzet van de sluipwesp Encarsia formosa is het lieveheersbeestje Delphasitus catalinae erg geschikt om haarden van kaswittevlieg op te ruimen. Omdat het lieveheersbeestje veel wittevlieg nodig heeft om zich te kunnen ontwikkelen, wordt nagegaan of een andere soort dan kaswittevlieg geschikt is om Delphastus catalinae in grotere aantallen in kassen met sierteelten in stand te houden. De wittevlieg Aleyrodes lonicerae blijkt geschikt als prooi voor Delphastus catalinae. Aleyrodes lonicerae werd gekweekt op zevenblad Aegopodium podagraria en aardbei Fragaria ‘Ellsanta’ maar vestigde zich niet op gerbera, hibiscus. Wel werden eieren gelegd op roos. In roos zou een andere soort wittevlieg kunnen worden toegepast.
    Natuurlijke vijanden in de sierteelt : van uitzetten naar in stand houden
    Grosman, Amir - \ 2013
    ornamental horticulture - plant protection - biological control agents - predators - supplementary feeding - predator prey relationships - augmentation - pest resistance
    Multitrophic effects of plant resistance: from basic ecology to application in transgenic crops
    Kos, M. - \ 2012
    Wageningen University. Promotor(en): Marcel Dicke; Louise Vet, co-promotor(en): Joop van Loon. - S.l. : s.n. - ISBN 9789461732064 - 303
    brassicaceae - verdedigingsmechanismen - insectenplagen - multitrofe interacties - parasitoïden - predatoren - glucosinolaten - vluchtige verbindingen - transgene planten - niet-doelorganismen - ecologische risicoschatting - brassicaceae - defence mechanisms - insect pests - multitrophic interactions - parasitoids - predators - glucosinolates - volatile compounds - transgenic plants - nontarget organisms - ecological risk assessment

    Plants have evolved a wide array of direct and indirect resistance traits that prevent or reduce herbivory by insects. The aim of this thesis was to study the effects of direct and indirect plant resistance traits on the multitrophic interactions between brassicaceous plants, leaf-chewing and phloem-sucking aboveground herbivores and their natural enemies, parasitoids and predators. Brassica oleracea cultivars and Arabidopsis thaliana ecotypes were used that differ in production of glucosinolates or emission of volatiles, secondary plant chemicals acting in direct and indirect resistance respectively. There was a considerable intraspecific variation in the multitrophic effects of plant resistance traits in both plant species. In the field, bottom-up forces (plant chemistry and morphology) appeared more important for herbivore abundance than plant-mediated top-down forces (attraction and arrestment of natural enemies). Under greenhouse conditions, glucosinolates affected the performance of herbivores and that of their natural enemies. The performance of both a generalist and a specialist caterpillar was negatively correlated with glucosinolates in the plant, whereas that of a parasitoid of the specialist caterpillar was positively correlated with glucosinolates. Performance of a specialist aphid was positively correlated with phloem glucosinolates, and the aphid selectively sequestered these glucosinolates. Glucosinolates and their volatile hydrolytic products correlated negatively with the performance and behaviour of one of the predators of this aphid, but positively with that of one of its parasitoids. These results suggest that direct and indirect resistance traits can be in conflict, but they can also work in concert to enhance resistance to herbivores, depending on the biology of the herbivore and carnivore involved. Transgenic A. thaliana plants engineered to emit larger amounts of volatile terpenoids repelled the aphid, attracted the parasitoid, but did not affect predator behaviour.

    These fundamental ecological results provided the background information required to strengthen ecological risk analysis for transgenicplants in the framework of the programme ‘Ecology Regarding Genetically modified Organisms’ funded by the Dutch government. The effects of transgenic plants on non-target organisms were compared with the baseline variation in the effects on non-target organisms that exists among conventional varieties or, in the case of A. thaliana, wild ecotypes. Four B. oleracea cultivars and three A. thaliana ecotypes were selected to represent the baseline variation. The baseline variation in effects on target and non-target organisms was relatively consistent over different environments, soil types and time. The effects of transgenic A. thaliana plants altered in direct and indirect resistance on non-target organisms were mostly within the baseline variation in these effects. Finally, the knowledge gained was applied to develop guidelines for governmental regulators that can be used to assess the potential ecological effects of transgenic crops on non-target organisms, in relation to baseline variation.

    Contaminant exposure in relation to spatio-temporal variation in diet composition: A case study of the little owl (Athene noctua)
    Schipper, A.M. ; Wijnhoven, S. ; Baveco, J.M. ; Brink, N.W. van den - \ 2012
    Environmental Pollution 163 (2012). - ISSN 0269-7491 - p. 109 - 116.
    river floodplains - small mammals - risk-assessment - cadmium accumulation - metal concentrations - food-chain - soil - predators - birds - heterogeneity
    We assessed dietary exposure of the little owl Athene noctua to trace metal contamination in a Dutch Rhine River floodplain area. Diet composition was calculated per month for three habitat types, based on the population densities of six prey types (earthworms, ground beetles and four small mammal species) combined with the little owl’s functional response to these prey types. Exposure levels showed a strong positive relationship with the dietary fraction of earthworms, but also depended on the dietary fraction of common voles, with higher common vole fractions resulting in decreasing exposure levels. Spatio-temporal changes in the availability of earthworms and common voles in particular resulted in considerable variation in exposure, with peaks in exposure exceeding a tentative toxicity threshold. These findings imply that wildlife exposure assessments based on a predefined, average diet composition may considerably underestimate local or intermittent peaks in exposure. --------------------------------------------------------------------------------
    Geen hoofdrol nutriënten in de afname van witvis in de Nederlandse binnenwateren
    Besseling, E. ; Hein, L.G. - \ 2011
    H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 44 (2011)17. - ISSN 0166-8439 - p. 37 - 39.
    visstand - biomassa - populatiedichtheid - binnenwateren - randmeren - eutrofiëring - predatoren - fish stocks - biomass - population density - inland waters - randmeren - eutrophication - predators
    Dit artikel geeft een overzicht van de verandering van witvisbestanden in een aantal Nederlandse binnenwateren en bespreekt de mogelijke oorzaken van deze veranderingen. Deze analyse geeft aan dat de vispopulaties van vier grote Nederlandse binnenwateren onder druk staan van met name de visserij. De invloed van andere factoren, voornamelijk actief biologisch beheer en een toename van het aantal aalscholvers, lijkt kleiner en verschilt per meer. Vermindering van de nutriëntenconcentraties in het water vormt niet de hoofdoorzaak van de afname van witvis.
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