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.

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    Cascading effects of defaunation on the coexistence of two specialized insect seed predators
    Peguero, Guille ; Muller-Landau, Helene C. ; Jansen, Patrick A. ; Wright, S.J. - \ 2017
    Journal of Animal Ecology 86 (2017)1. - ISSN 0021-8790 - p. 136 - 146.
    Attalea butyracea - facilitation - intraguild predation - multi-trophic interactions - Panama - seed beetles - seed fate - top-down control - trophic cascades

    Identification of the mechanisms enabling stable coexistence of species with similar resource requirements is a central challenge in ecology. Such coexistence can be facilitated by species at higher trophic levels through complex multi-trophic interactions, a mechanism that could be compromised by ongoing defaunation. We investigated cascading effects of defaunation on Pachymerus cardo and Speciomerus giganteus, the specialized insect seed predators of the Neotropical palm Attalea butyracea, testing the hypothesis that vertebrate frugivores and granivores facilitate their coexistence. Laboratory experiments showed that the two seed parasitoid species differed strongly in their reproductive ecology. Pachymerus produced many small eggs that it deposited exclusively on the fruit exocarp (exterior). Speciomerus produced few large eggs that it deposited exclusively on the endocarp, which is normally exposed only after a vertebrate handles the fruit. When eggs of the two species were deposited on the same fruit, Pachymerus triumphed only when it had a long head start, and the loser always succumbed to intraguild predation. We collected field data on the fates of 6569 Attalea seeds across sites in central Panama with contrasting degrees of defaunation and wide variation in the abundance of vertebrate frugivores and granivores. Speciomerus dominated where vertebrate communities were intact, whereas Pachymerus dominated in defaunated sites. Variation in the relative abundance of Speciomerus across all 84 sampling sites was strongly positively related to the proportion of seeds attacked by rodents, an indicator of local vertebrate abundance. Synthesis. We show that two species of insect seed predators relying on the same host plant species are niche differentiated in their reproductive strategies such that one species has the advantage when fruits are handled promptly by vertebrates and the other when they are not. Defaunation disrupts this mediating influence of vertebrates and strongly favours one species at the expense of the other, providing a case study of the cascading effects of defaunation and its potential to disrupt coexistence of non-target species, including the hyperdiverse phytophagous insects of tropical forests.

    Data from: Cascading effects of defaunation on the coexistence of two specialized insect seed predators
    Peguero, Guille ; Muller-Landau, Helene C. ; Jansen, P.A. ; Wright, S.J. - \ 2016
    University of Antwerpen
    facilitation - intraguild predation - multi-trophic interactions - seed fate - seed beetles - top-down control - trophic cascades - Attalea butyracea - Pachymerus cardo - Speciomerus giganteus
    Identification of the mechanisms enabling stable coexistence of species with similar resource requirements is a central challenge in ecology. Such coexistence can be facilitated by species at higher trophic levels through complex multi-trophic interactions, a mechanism that could be compromised by ongoing defaunation. We investigated cascading effects of defaunation on Pachymerus cardo and Speciomerus giganteus, the specialized insect seed predators of the Neotropical palm Attalea butyracea, testing the hypothesis that vertebrate frugivores and granivores facilitate their coexistence. Laboratory experiments showed that the two seed parasitoid species differed strongly in their reproductive ecology. Pachymerus produced many small eggs that it deposited exclusively on the fruit exocarp (exterior). Speciomerus produced few large eggs that it deposited exclusively on the endocarp, which is normally exposed only after a vertebrate handles the fruit. When eggs of the two species were deposited on the same fruit, Pachymerus triumphed only when it had a long head start, and the loser always succumbed to intraguild predation. We collected field data on the fates of 6569 Attalea seeds across sites in central Panama with contrasting degrees of defaunation and wide variation in the abundance of vertebrate frugivores and granivores. Speciomerus dominated where vertebrate communities were intact, whereas Pachymerus dominated in defaunated sites. Variation in the relative abundance of Speciomerus across all 84 sampling sites was strongly positively related to the proportion of seeds attacked by rodents, an indicator of local vertebrate abundance. Synthesis. We show that two species of insect seed predators relying on the same host plant species are niche differentiated in their reproductive strategies such that one species has the advantage when fruits are handled promptly by vertebrates and the other when they are not. Defaunation disrupts this mediating influence of vertebrates and strongly favours one species at the expense of the other, providing a case study of the cascading effects of defaunation and its potential to disrupt coexistence of non-target species, including the hyperdiverse phytophagous insects of tropical forests.
    Native and Non-Native Plants Provide Similar Refuge to Invertebrate Prey, but Less than Artificial Plants
    Grutters, B.M.C. ; Pollux, B.J.A. ; Verberk, W.C.E.P. ; Bakker, E.S. - \ 2015
    PLoS ONE 10 (2015)4. - ISSN 1932-6203 - 11 p.
    submerged aquatic vegetation - structural complexity - habitat complexity - foraging success - intraguild predation - largemouth bass - fish predation - hunting mode - body-size - food-web
    Non-native species introductions are widespread and can affect ecosystem functioning by altering the structure of food webs. Invading plants often modify habitat structure, which may affect the suitability of vegetation as refuge and could thus impact predator-prey dynamics. Yet little is known about how the replacement of native by non-native vegetation affects predator-prey dynamics. We hypothesize that plant refuge provisioning depends on (1) the plant’s native status, (2) plant structural complexity and morphology, (3) predator identity, and (4) prey identity, as well as that (5) structurally similar living and artificial plants provide similar refuge. We used aquatic communities as a model system and compared the refuge provided by plants to macroinvertebrates (Daphnia pulex, Gammarus pulex and damselfly larvae) in three short-term laboratory predation experiments. Plant refuge provisioning differed between plant species, but was generally similar for native (Myriophyllum spicatum, Ceratophyllum demersum, Potamogeton perfoliatus) and non-native plants (Vallisneria spiralis, Myriophyllum heterophyllum, Cabomba caroliniana). However, plant refuge provisioning to macroinvertebrate prey depended primarily on predator (mirror carp: Cyprinus carpio carpio and dragonfly larvae: Anax imperator) and prey identity, while the effects of plant structural complexity were only minor. Contrary to living plants, artificial plant analogues did improve prey survival, particularly with increasing structural complexity and shoot density. As such, plant rigidity, which was high for artificial plants and one of the living plant species evaluated in this study (Ceratophyllum demersum), may interact with structural complexity to play a key role in refuge provisioning to specific prey (Gammarus pulex). Our results demonstrate that replacement of native by structurally similar non-native vegetation is unlikely to greatly affect predator-prey dynamics. We propose that modification of predator-prey interactions through plant invasions only occurs when invading plants radically differ in growth form, density and rigidity compared to native plants.
    Species’ traits influence ground beetle responses to farm and landscape level agricultural intensification in Europe
    Winqvist, C. ; Bengtsson, J. ; Öckinger, E. ; Aavik, T. ; Berendse, F. ; Clement, L.W. ; Geiger, F. - \ 2014
    Journal of Insect Conservation 18 (2014)5. - ISSN 1366-638X - p. 837 - 846.
    carabid beetle - habitat fragmentation - biological-control - intraguild predation - functional diversity - spatial scales - arable crops - context - biodiversity - land
    Agricultural intensification may result in important shifts in insect community composition and function, but this remains poorly explored. Studying how groups of species with shared traits respond to local and landscape scale land-use management can reveal mechanisms behind such observed impacts. We tested if ground beetles (Coleoptera: Carabidae) divided into trait groups based on body sizes, wing morphologies and dietary preferences respond differently to farming practise (organic and conventional), farming intensity (measured as yield) and landscape complexity (measured as the proportion of arable land within a 1,000 m radius) across Europe. We used data from 143 farms in five regions in northern and central Europe. Organic farms did not differ in abundance or richness of any trait group compared to conventional farms. As farm scale intensity (yield) increased, overall abundance of beetles decreased, but abundances of small and medium sized beetles, as well as that of wingless beetles, were unaffected. Overall species richness was not affected by yield, whereas consideration of traits revealed that phytophagous and omnivorous beetles were less species rich on farms with high yields. Increasing the proportion of arable land in the landscape increased overall beetle abundance. This was driven by an increase in omnivorous beetles. The total species richness was not affected by an increase in the proportion arable land, although the richness of wingless beetles was found to increase. Potential effects on ecosystem functioning need to be taken into account when designing schemes to maintain agricultural biodiversity, because species with different ecological traits respond differently to local management and landscape changes.
    Natural enemy-mediated indirect interactions among prey species: potential for enhancing biocontrol services in agroecosystems
    Chailleux, A. ; Mohl, E.K. ; Teixeira Alves, M. ; Messelink, G.J. ; Desneux, N. - \ 2014
    Pest Management Science 70 (2014)12. - ISSN 1526-498X - p. 1769 - 1779.
    quantitative food webs - improving biological-control - orius-insidiosus hemiptera - corn leaf aphid - apparent competition - alternative prey - intraguild predation - generalist predators - soybean aphid - macrolophus-caliginosus
    Understanding how arthropod pests and their natural enemies interact in complex agroecosystems is essential for pest management programmes. Theory predicts that prey sharing a predator, such as a biological control agent, can indirectly reduce each other's density at equilibrium (apparent competition). From this premise, we (i) discuss the complexity of indirect interactions among pests in agroecosystems and highlight the importance of natural enemy-mediated indirect interactions other than apparent competition, (ii) outline factors that affect the nature of enemy-mediated indirect interactions in the field and (iii) identify the way to manipulate enemy-mediated interactions for biological control. We argue that there is a need to increase the link between community ecology theory and biological control to develop better agroecological methods of crop protection via conservation biological control. In conclusion, we identify (i) interventions to be chosen depending on agroecosystem characteristics and (ii) several lines of research that will improve the potential for enemy-mediated indirect interactions to be applied to biological control. © 2014 Society of Chemical Industry
    Approaches to conserving natural enemy populations in greenhouse crops: current methods and future prospects
    Messelink, G.J. ; Bennison, J. ; Alomar, O. ; Ingegno, B.L. ; Tavella, L. ; Shipp, L. ; Palevsky, E. ; Wäckers, F.L. - \ 2014
    BioControl 59 (2014)4. - ISSN 1386-6141 - p. 377 - 393.
    biological-control agents - mite neoseiulus-californicus - life-history characteristics - bug macrolophus-caliginosus - orius-insidiosus say - tuta-absoluta - pest-control - frankliniella-occidentalis - intraguild predation - generalist predators
    Biological pest control in greenhouse crops is usually based on periodical releases of mass-produced natural enemies, and this method has been successfully applied for decades. However, in some cases there are shortcomings in pest control efficacy, which often can be attributed to the poor establishment of natural enemies. Their establishment and population numbers can be enhanced by providing additional resources, such as alternative food, prey, hosts, oviposition sites or shelters. Furthermore, natural enemy efficacy can be enhanced by using volatiles, adapting the greenhouse climate, avoiding pesticide side-effects and minimizing disrupting food web complexities. The special case of high value crops in a protected greenhouse environment offers tremendous opportunities to design and manage the system in ways that increase crop resilience to pest infestations. While we have outlined opportunities and tools to develop such systems, this review also identifies knowledge gaps, where additional research is needed to optimize these tools.
    Nonlinearities Lead to Qualitative Differences in Population Dynamics of Predator-Prey Systems
    Ameixa, O. ; Messelink, G.J. ; Kindlmann, P. - \ 2013
    PLoS ONE 8 (2013)4. - ISSN 1932-6203
    intraguild predation - biological-control - aphid populations - field experiments - interspecific competition - ecological communities - emergent impacts - natural enemies - suppression - consequences
    Since typically there are many predators feeding on most herbivores in natural communities, understanding multiple predator effects is critical for both community and applied ecology. Experiments of multiple predator effects on prey populations are extremely demanding, as the number of treatments and the amount of labour associated with these experiments increases exponentially with the number of species in question. Therefore, researchers tend to vary only presence/absence of the species and use only one (supposedly realistic) combination of their numbers in experiments. However, nonlinearities in density dependence, functional responses, interactions between natural enemies etc. are typical for such systems, and nonlinear models of population dynamics generally predict qualitatively different results, if initial absolute densities of the species studied differ, even if their relative densities are maintained. Therefore, testing combinations of natural enemies without varying their densities may not be sufficient. Here we test this prediction experimentally. We show that the population dynamics of a system consisting of 2 natural enemies (aphid predator Adalia bipunctata (L.), and aphid parasitoid, Aphidius colemani Viereck) and their shared prey (peach aphid, Myzus persicae Sulzer) are strongly affected by the absolute initial densities of the species in question. Even if their relative densities are kept constant, the natural enemy species or combination thereof that most effectively suppresses the prey may depend on the absolute initial densities used in the experiment. Future empirical studies of multiple predator – one prey interactions should therefore use a two-dimensional array of initial densities of the studied species. Varying only combinations of natural enemies without varying their densities is not sufficient and can lead to misleading results.
    Comment on "Invasive Harlequin Ladybird Carries Biological Weapons Against Native Competitors"
    Jong, P.W. de; Lenteren, J.C. van; Raak-van den Berg, C.L. - \ 2013
    Science 341 (2013)6152. - ISSN 0036-8075
    intraguild predation - harmonia-axyridis - coccinellidae - coleoptera
    We comment on the implications that Vilcinskas et al. (Reports, 17 May 2013, p. 862) attach to the finding that the exotic, invasive ladybird Harmonia axyridis carries microsporidia to which this species is insensitive but that is lethal to species that are native to the invaded areas. The authors suggest that these microsporidia might serve as “biological weapons” against the native competitors, but we cast doubt on the importance of this suggestion in the field.
    Biological control of aphids in the presence of thrips and their enemies
    Messelink, G.J. ; Bloemhard, C.M.J. ; Sabelis, M.W. ; Janssen, A. - \ 2013
    BioControl 58 (2013)1. - ISSN 1386-6141 - p. 45 - 55.
    intraguild predation - generalist predators - alternative prey - apparent competition - suppression - biocontrol - biodiversity - communities - parasitoids - predictions
    Generalist predators are often used in biological control programs, although they can be detrimental for pest control through interference with other natural enemies. Here, we assess the effects of generalist natural enemies on the control of two major pest species in sweet pepper: the green peach aphid Myzus persicae (Sulzer) and the western flower thrips Frankliniella occidentalis (Pergande). In greenhouses, two commonly used specialist natural enemies of aphids, the parasitoid Aphidius colemani Viereck and the predatory midge Aphidoletes aphidimyza (Rondani), were released together with either Neoseiulus cucumeris Oudemans, a predator of thrips and a hyperpredator of A. aphidimyza, or Orius majusculus (Reuter), a predator of thrips and aphids and intraguild predator of both specialist natural enemies. The combined use of O. majusculus, predatory midges and parasitoids clearly enhanced the suppression of aphids and consequently decreased the number of honeydew-contaminated fruits. Although intraguild predation by O. majusculus on predatory midges and parasitoids will have affected control of aphids negatively, this was apparently offset by the consumption of aphids by O. majusculus. In contrast, the hyperpredator N. cucumeris does not prey upon aphids, but seemed to release aphids from control by consuming eggs of the midge. Both N. cucumeris and O. majusculus did not affect rates of aphid parasitism by A. colemani. Thrips were also controlled effectively by O. majusculus. A laboratory experiment showed that adult predatory bugs feed on thrips as well as aphids and have no clear preference. Thus, the presence of thrips probably promoted the establishment of the predatory bugs and thereby the control of aphids. Our study shows that intraguild predation, which is potentially negative for biological control, may be more than compensated by positive effects of generalist predators, such as the control of multiple pests, and the establishment of natural enemies prior to pest invasions. Future work on biological control should focus on the impact of species interactions in communities of herbivorous arthropods and their enemies.
    Size-based species interactions shape herring and cod population dynamics in the face of exploitation
    Denderen, P.D. van; Kooten, T. van - \ 2013
    Ecosphere 4 (2013)10. - ISSN 2150-8925
    north-sea cod - clupea-harengus - intraguild predation - prey - model - recruitment - recovery - biomass - management - fisheries
    Size-specific competition and predation interactions often link the population dynamics of fish species in their response to exploitation. The effects of harvesting on interacting fish species is of increasing relevance as more and more fish populations worldwide are reduced by fishing. When stocks are harvested, effects of harvesting may percolate to populations of other species with which it interacts through competition, predation, etcetera. When multiple species are exploited, this can lead to interactions between fisheries, mediated by ecological interactions. Nevertheless, most fish stocks are managed using a single-species framework. We studied how single-species explanations of historical population dynamics work out when size-based interactions between harvested species are taken into account. We have taken as a case study the dynamics of cod (Gadus morhua) and herring (Clupea harengus) in the North Sea. These dynamics are generally considered to be shaped by fishing pressure on and food availability to single species. Our results indicate that the explanatory power of these factors is maintained with the inclusion of species interactions, but the processes leading to the observed patterns are altered as the fates of the species are interdependent. The sign and magnitude of the interaction between the species depends on the state of the populations, their exploitation history and environmental factors such as resource productivity. This context-dependent response to changing fishery intensity has important ramifications for management. We show that management plans for the exploitation of either one of these species, or for the recovery of North Sea cod, which do not account for these subtle interactions, may fail or backfire. Hence, such interactions link the fate of these species in complex ways, which must be taken into consideration for successful management of their exploitation, including harvesting at maximum sustainable yield, as we move towards an ecosystem-based management of marine fisheries.
    Amazon poison frogs (Ranitomeya amazonica) use different phytotelm characteristics to determine their suitablility for egg and tadpole deposition
    Poelman, E.H. ; Wijngaarden, R.P.A. van; Raaijmakers, C.E. - \ 2013
    Evolutionary Ecology 27 (2013)4. - ISSN 0269-7653 - p. 661 - 674.
    dendrobates-ventrimaculatus - parental care - intraguild predation - habitat selection - oviposition-site - cannibalism - competition - strategies - anura - size
    Parents have to assess the multivariate characteristics of their reproductive sites to maximize their reproductive success through offspring performance. In addition, they may provide care to ensure optimal performance of their offspring. In poison frogs it has been identified that ecological characteristics of reproductive sites may underlie transitions in the involvement of parental sexes in care for offspring. To elucidate the ecological factors that may drive these transitions, it is important to understand which characteristics poison frogs use to assess the quality of their reproductive site. We studied the use of small water bodies in leaf axils of bromeliads, phytotelmata, for egg and tadpole deposition by Amazon poison frogs (Ranitomeya amazonica). We compared phytotelm quality characteristics for preferred egg and tadpole deposition sites and used two choice tests with plastic cups to study the causal relationship with tadpole deposition for the identified characteristics. The differences among quality characteristics of deposition sites were largest among bromeliad species, and for egg or tadpole deposition different bromeliad species were preferred. However, males were also selective in the leaf axils within a bromeliad species that they used for egg or tadpole deposition. Eggs were deposited in small, resource limited water bodies that were close to the forest floor. Tadpoles were deposited in leaf axils holding resource-rich phytotelmata with larger water volumes. Preference of detritus containing water over clear water in choice tests confirmed that Amazon poison frogs assess quality of their tadpole deposition sites on food availability. We conclude that preference for large water volume and resource rich phytotelmata plays an important role in determining male involvement in parental care and speculate that distribution of preferred resources may bring about selection on female involvement in parental care.
    Impact of grazing management on hibernating caterpillars of the butterfly Melitaea cinxia in calcareous grasslands
    Noordwijk, C.G.E. ; Flierman, D.E. ; Remke, E. ; Wallis de Vries, M.F. ; Berg, M.P. - \ 2012
    Journal of Insect Conservation 16 (2012)6. - ISSN 1366-638X - p. 909 - 920.
    life-history strategies - restoration management - seminatural grasslands - intraguild predation - phytophagous insects - species-diversity - conservation - intensity - herbivores - vegetation
    Semi-natural grasslands are increasingly grazed by large herbivores for nature conservation purposes. For many insects such grazing is essential for the conservation of their habitat, but at the same time, populations decrease at high grazing intensity. We hypothesised that grazing management may cause increased butterfly mortality, especially for life-stages with low mobility, such as hibernating caterpillars. To test this, we measured the effect of sheep grazing on overwinter larval survival. We used the Glanville fritillary (Melitaea cinxia), which has gregarious caterpillars hibernating in silk nests, as a model species. Caterpillar nests were monitored throughout the hibernating period in calcareous grassland reserves with low and high intensity sheep grazing and in an ungrazed control treatment. After grazing, 64 % of the nests at the high intensity grazing treatment were damaged or missing, compared to 8 and 12 % at the ungrazed and low intensity grazing treatment, respectively. Nest volume and caterpillar survival were 50 % lower at the high intensity grazing treatment compared to both ungrazed and low intensity grazing treatments. Nest damage and increased mortality were mainly caused by incidental ingestion of the caterpillars by the sheep. It is likely that grazing similarly affects other invertebrates, depending on their location within the vegetation and their ability to actively avoid herbivores. This implies that the impact of grazing strongly depends on the timing of this management in relation to the phenology of the species. A greater focus on immature and inactive life-stages in conservation policy in general and particularly in action plans for endangered species is required to effectively preserve invertebrate diversity.
    Dietary overlap between the potential competitors herring, sprat and anchovy in the North Sea
    Raab, K.E. ; Nagelkerke, L.A.J. ; Boeree, C. ; Rijnsdorp, A.D. ; Temming, A. ; Dickey-Collas, M. - \ 2012
    Marine Ecology Progress Series 470 (2012). - ISSN 0171-8630 - p. 101 - 111.
    engraulis-encrasicolus l. - central baltic sea - clupea-harengus - feeding-behavior - intraguild predation - trophic interactions - population-dynamics - mediterranean sea - fish eggs - irish sea
    European anchovy Engraulis encrasicolus increased its abundance and distribution in the North Sea during the mid-1990s and may consume similar zooplankton to and/or compete with other occupants of the North Sea like herring Clupea harengus and sprat Sprattus sprattus. The diets of adult anchovy, sprat and juvenile herring of comparable sizes, sampled close in time and space, were compared to understand how the 3 species prey on zooplankton and establish whether their diets overlap or not. Anchovy was found to be more generalist, consuming a higher diversity of prey items. Herring was more specialized, with low diversity of food items. Sprat was intermediate between anchovy and herring. The dietary overlap between anchovy and sprat was highest, followed by herring and sprat before anchovy and herring. The mean weight of stomach contents did not differ between species. We conclude that of the 3 species, anchovy is likely to be the least affected by changing plankton communities.
    Winter survival of Harmonia axyridis in The Netherlands
    Raak-van den Berg, C.L. ; Stam, J.M. ; Jong, P.W. de; Hemerik, L. ; Lenteren, J.C. van - \ 2012
    Biological Control 60 (2012)1. - ISSN 1049-9644 - p. 68 - 76.
    asian lady beetle - septempunctata col.-coccinellidae - environmental risk-assessment - biological-control agents - adalia-bipunctata l - coleoptera-coccinellidae - pallas coleoptera - intraguild predation - united-states - overwintering survival
    Since the establishment of Harmonia axyridis in Europe, populations of native ladybirds have decreased. Overwintering survival is one of the aspects of the biology of H. axyridis that may contribute to its firm establishment in and invasion of a new area. In this study winter survival of five wild H. axyridis populations was assessed under natural and semi-natural conditions, with a focus on the potential influence of location and orientation on winter survival. Overwintering survival of H. axyridis in the Netherlands is high: 70.8–88.2%. When overwintering at one central site, populations sampled at five locations showed statistically significant different mortality rates. Furthermore, winter survival of H. axyridis at the sample sites was higher when beetles were hibernating at the southwestern sides of buildings, where most aggregations of ladybirds were found. Survival was higher at sheltered sites compared to exposed sites. Harmonia axyridis has a comparable or higher overwintering survival than most common native ladybird species. A high overwintering survival results in a large post-hibernation population in spring, leading to a rapid population build-up. Thus, the high winter survival probably contributes to the success of the exotic H. axyridis
    Intrinsic competition between two secondary hyperparasitoids results in temporal trophic switch
    Harvey, J.A. ; Pashalidou, F.G. ; Soler, R. ; Bezemer, T.M. - \ 2011
    Oikos 120 (2011)2. - ISSN 0030-1299 - p. 226 - 233.
    solitary parasitoid wasp - physiological suppression - leptopilina-heterotoma - insect parasitoids - interspecific competition - intraguild predation - host discrimination - aphytis-melinus - lysibia-nana - superparasitism
    Interspecific competition amongst parasitoids is important in shaping the evolution of life-history strategies in these insects as well as community structure. Competition for hosts may occur between adult female parasitoids (‘extrinsic’ competition) or their progeny (‘intrinsic’ competition). Here, we examined intrinsic competition between two solitary secondary hyperparasitoids, Lysibia nana and Gelis agilis in cocoons of a primary parasitoid, Cotesia glomerata. Each species was allowed to sting hosts previously parasitized by the other at 24 h time intervals over the course of 144 h (6 days). When hosts were attacked simultaneously, neither species was dominant although the species to attack first won most encounters when it had a 24–48 h head start. However, after this time there was dramatic shift in the outcome with G. agilis dominating in all hosts > 72-h old, regardless of which species had parasitized C. glomerata first. G. agilis larvae, which initially had competed with L. nana for control of C. glomerata resources, began attacking the larvae of L. nana, whereas L. nana rejected hosts with older G. agilis larvae or pupae. Effects of multiparasitism also affected the development time and adult mass of the winning parasitoid. Our results reveal a shift in the trophic status of G. agilis from C. glomerata (in younger hosts) to L. nana (in older hosts), the first time such a phenomenon has been reported in parasitoids
    Hyperpredation by generalist predatory mites disrupts biological control of aphids by the aphidophagous gall midge Aphidoletes aphidimyza
    Messelink, G.J. ; Bloemhard, C.M.J. ; Cortes, J.A. ; Sabelis, M.W. ; Jansen, A. - \ 2011
    Biological Control 57 (2011)3. - ISSN 1049-9644 - p. 246 - 252.
    intraguild predation - phytoseiid predators - neoseiulus-cucumeris - amblyseius-swirskii - bemisia-tabaci - acari phytoseiidae - prey communities - alternative food - myzus-persicae - control agents
    Biological control of different species of pest with various species of generalist predators can potentially disrupt the control of pests through predator-predator interactions. We evaluate the impact of three species of generalist predatory mites on the biological control of green peach aphids, Myzus persicae (Sulzer) with the aphidophagous gall midge Aphidoletes aphidimyza (Rondani). The predatory mites tested were Neoseiulus cucumeris (Oudemans), Iphiseius degenerans (Berlese) and Amblyseius swirskii Athias–Henriot, which are all commonly used for pest control in greenhouse sweet pepper. All three species of predatory mites were found to feed on eggs of A. aphidimyza, even in the presence of abundant sweet pepper pollen, an alternative food source for the predatory mites. In a greenhouse experiment on sweet pepper, all three predators significantly reduced population densities of A. aphidimyza, but aphid densities only increased significantly in the presence of A. swirskii when compared to the treatment with A. aphidimyza only. This stronger effect of A. swirskii can be explained by the higher population densities that this predator reached on sweet pepper plants compared to the other two predator species. An additional experiment showed that female predatory midges do not avoid oviposition sites with the predator A. swirskii. On the contrary, they even deposited more eggs on plants with predatory mites than on plants without. Hence, this study shows that disruption of aphid control by predatory mites is a realistic scenario in sweet pepper, and needs to be considered when optimizing biological control strategies.
    Anchovy Engraulis encrasicolus diet in the North and Baltic Seas
    Raab, K.E. ; Nagelkerke, L.A.J. ; Boerée, L.A.J. ; Rijnsdorp, A.D. ; Temming, A. ; Dickey-Collas, M. - \ 2011
    Journal of Sea Research 65 (2011)1. - ISSN 1385-1101 - p. 131 - 140.
    herring clupea-harengus - cod gadus-morhua - haddock melanogrammus-aeglefinus - whiting merlangius-merlangus - long-term changes - intraguild predation - feeding-behavior - irish sea - sprattus-sprattus - mediterranean sea
    The diet of anchovy (Engraulis encrasicolus) in the North and Baltic Seas was studied using stomach analysis from four sampling events in different areas. Zooplanktivory was confirmed; the most frequent prey items (in over 40% of stomachs) were copepods, malacostracan larvae and fish larvae. In the Baltic Sea, Paracalanus spp. and Pseudocalanus spp. were important in relative terms; in the German Bight, Temora spp. dominated the stomach contents. Relative abundances of prey items varied with area more than absolute abundance or presence absence of items. Moreover, the level of resolution of prey categories influenced which prey categories were considered to be most important in driving variability in stomach content. Anchovy diet is broad across the seasons, years and areas sampled, suggesting that it is not a specialist feeder in the North Sea. The similarity of diet between anchovy and other clupeids, as well as anchovy consumption of larval fish, makes the new increased anchovy population a potential intraguild predator of commercial species like herring.
    Relationship between the ability to penetrate complex webs of Tetranychus spider mites and the ability of thread-cutting behavior in phytoseiid predatory mites
    Shimoda, T. ; Kishimoto, H. ; Takabayashi, J. ; Amano, H. ; Dicke, M. - \ 2010
    Biological Control 53 (2010)3. - ISSN 1049-9644 - p. 273 - 279.
    womersleyi schicha acari - kanzawai kishida acari - intraguild predation - amblyseius-womersleyi - natural enemies - prey preference - food - specialization - populations - orchards
    Predatory mites, that are important natural enemies of Tetranychus spider mites, are less hindered by complex webs of the spider mites than are other predatory mites that are natural enemies of other pest herbivores. This can be partly explained by their chaetotaxy, a morphological protection against the webs. However, it has up to now been unclear whether the ability to penetrate complex webs is related to the ability of thread-cutting behavior to reduce the effects of the webs. The two predatory mites Neo-seiulus cucumeris and Typhlodromus vulgaris, that are natural enemies of other pest herbivores, were often entrapped by the sticky silken threads while moving within the complex web produced by the two-spotted spider mites Tetranychus urticae. Once captured, their movements and foraging activities were hindered until their escape from entrapment. In contrast, N. womersleyi and Phytoseiulus persimilis, that are important natural enemies of Tetranychus mites, were significantly less frequently entrapped by the web and for shorter periods. Furthermore, N. womersleyi and P. persimilis cut significantly more silken threads within the web than did N. cucumeris and T. vulgaris. The different behavioral activities exhibited by N. cucumeris and N. womersleyi could not be explained by their rearing conditions (i.e., past experience with complex webs). These results supported the hypothesis and might offer an ecological indicator for distinguishing potential important natural enemies of Tetranychus mites from less useful types. (c) 2010 Elsevier Inc. All rights reserved.
    Omnivory by planktivores stabilizes plankton dynamics, but may either promote or reduce algal biomass
    Attayde, J.L. ; Nes, E.H. van; Araujo, A.I.L. ; Corso, G. ; Scheffer, M. - \ 2010
    Ecosystems 13 (2010)3. - ISSN 1432-9840 - p. 410 - 420.
    tilapia oreochromis-niloticus - top-down control - filter-feeding fish - food webs - shallow lakes - silver carp - intraguild predation - nile tilapia - hypophthalmichthys-molitrix - enclosure experiment
    Classical models of phytoplankton–zooplankton interaction show that with nutrient enrichment such systems may abruptly shift from limit cycles to stable phytoplankton domination due to zooplankton predation by planktivorous fish. Such models assume that planktivorous fish eat only zooplankton, but there are various species of filter-feeding fish that may also feed on phytoplankton. Here, we extend these classical models to systematically explore the effects of omnivory by planktivorous fish. Our analysis indicates that if fish forage on phytoplankton in addition to zooplankton, the alternative attractors predicted by the classical models disappear for all realistic parameter settings, even if omnivorous fish have a strong preference for zooplankton. Our model also shows that the level of fish biomass above which zooplankton collapse should be higher when fish are omnivorous than when fish are zooplanktivorous. We also used the model to explore the potential effects of the now increasingly common practice of stocking lakes with filter-feeding fish to control cyanobacteria. Because omnivorous filter-feeding fish forage on phytoplankton as well as on the main grazers of phytoplankton, the net effect of such fish on the phytoplankton biomass is not obvious. Our model suggests that there may be a unimodal relationship between the biomass of omnivorous filter-feeding fish and the biomass of phytoplankton. This implies that to manage for reductions in phytoplankton biomass, heavy stocking or strong reduction of such fish is best
    "Protected biological control"- Biological pest management in the greenhouse industry
    Pilkington, L.J. ; Messelink, G.J. ; Lenteren, J.C. van; Mottee, K. Le - \ 2010
    Biological Control 52 (2010)3. - ISSN 1049-9644 - p. 216 - 220.
    parasitoid encarsia-formosa - western flower thrips - phytoseiid predators - control agents - intraguild predation - biocontrol - populations - pesticides - cucumber - benefits
    This paper briefly describes the foundations and characteristics of biological control in protected cropping and what drivers are behind adoption of this management system within this industry. Examining a brief history of biological control in greenhouses and what makes it a successful management strategy within the industry, the authors describe the rapid growth of biological control in parts of Europe and what this may mean for the industry in other parts of the world. The reaction of the greenhouse industry to several consumer led campaigns aimed at reducing the incidence of pesticides in the marketplace may be replicated in many other parts of the world. The size and robustness of the biological control industry in greenhouses, which is a reflection of the inherent characteristics of this industry that lends itself to biological control, is strong and growing with indications that this trend will be followed in many areas of the world
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