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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    Plant responses to butterfly oviposition partly explain preference–performance relationships on different brassicaceous species
    Griese, Eddie ; Pineda, Ana ; Pashalidou, Foteini G. ; Iradi, Eleonora Pizarro ; Hilker, Monika ; Dicke, Marcel ; Fatouros, Nina E. - \ 2020
    Oecologia 192 (2020)2. - ISSN 0029-8549 - p. 463 - 475.
    Egg-killing - Hypersensitive response - Oviposition-induced - Pieridae - Priming

    The preference–performance hypothesis (PPH) states that herbivorous female insects prefer to oviposit on those host plants that are best for their offspring. Yet, past attempts to show the adaptiveness of host selection decisions by herbivores often failed. Here, we tested the PPH by including often neglected oviposition-induced plant responses, and how they may affect both egg survival and larval weight. We used seven Brassicaceae species of which most are common hosts of two cabbage white butterfly species, the solitary Pieris rapae and gregarious P. brassicae. Brassicaceous species can respond to Pieris eggs with leaf necrosis, which can lower egg survival. Moreover, plant-mediated responses to eggs can affect larval performance. We show a positive correlation between P. brassicae preference and performance only when including the egg phase: 7-day-old caterpillars gained higher weight on those plant species which had received most eggs. Pieris eggs frequently induced necrosis in the tested plant species. Survival of clustered P. brassicae eggs was unaffected by the necrosis in most tested species and no relationship between P. brassicae egg survival and oviposition preference was found. Pieris rapae preferred to oviposit on plant species most frequently expressing necrosis although egg survival was lower on those plants. In contrast to the lower egg survival on plants expressing necrosis, larval biomass on these plants was higher than on plants without a necrosis. We conclude that egg survival is not a crucial factor for oviposition choices but rather egg-mediated responses affecting larval performance explained the preference–performance relationship of the two butterfly species.

    Bacterial Symbionts in Lepidoptera : Their Diversity, Transmission, and Impact on the Host
    Paniaqua Voirol, Luis R. ; Frago, Enric ; Kaltenpoth, Martin ; Hilker, M. ; Fatouros, N.E. - \ 2018
    Frontiers in Microbiology 9 (2018). - ISSN 1664-302X
    The insect’s microbiota is well acknowledged as a “hidden” player influencing essential insect traits. The gut microbiome of butterflies and moths (Lepidoptera) has been shown to be highly variable between and within species, resulting in a controversy on the functional relevance of gut microbes in this insect order. Here, we aim to (i) review current knowledge on the composition of gut microbial communities across Lepidoptera and (ii) elucidate the drivers of the variability in the lepidopteran gut microbiome and provide an overview on (iii) routes of transfer and (iv) the putative functions of microbes in Lepidoptera. To find out whether Lepidopterans possess a core gut microbiome, we compared studies of the microbiome from 30 lepidopteran species. Gut bacteria of the Enterobacteriaceae, Bacillaceae, and Pseudomonadaceae families were the most widespread across species, with Pseudomonas, Bacillus, Staphylococcus, Enterobacter, and Enterococcus being the most common genera.
    Several studies indicate that habitat, food plant, and age of the host insect can greatly impact the gut microbiome, which contributes to digestion, detoxification, or defense against natural enemies. We mainly focus on the gut microbiome, but we also include some examples of intracellular endosymbionts. These symbionts are present across a broad range of insect taxa and are known to exert different effects on their host, mostly including nutrition and reproductive manipulation. Only two intracellular bacteria genera
    (Wolbachia and Spiroplasma) have been reported to colonize reproductive tissues of Lepidoptera, affecting their host’s reproduction. We explore routes of transmission of both gut microbiota and intracellular symbionts and have found that these microbes may be horizontally transmitted through the host plant, but also vertically via the egg stage. More detailed knowledge about the functions and plasticity of the microbiome in Lepidoptera may provide novel leads for the control of lepidopteran pest species.
    Plant response to butterfly eggs : Inducibility, severity and success of egg-killing leaf necrosis depends on plant genotype and egg clustering /631/158/2456 /631/158/856 article
    Griese, Eddie ; Dicke, Marcel ; Hilker, Monika ; Fatouros, Nina E. - \ 2017
    Scientific Reports 7 (2017)1. - ISSN 2045-2322
    Plants employ various defences killing the insect attacker in an early stage. Oviposition by cabbage white butterflies (Pieris spp.) on brassicaceous plants, including Brassica nigra, induces a hypersensitive response (HR) - like leaf necrosis promoting desiccation of eggs. To gain a deeper insight into the arms race between butterflies and plants, we conducted field and greenhouse experiments using different B. nigra genotypes. We investigated variation in HR and consequent survival of P. brassicae egg clusters. Impact of egg density, distribution type and humidity on HR formation and egg survival was tested. HR differed among plant genotypes as well as plant individuals. Egg density per plant did not affect HR formation. Remarkably, egg survival did not depend on the formation of HR, unless butterflies were forced to lay single eggs. Larval hatching success from single eggs was lower on plants expressing HR. This may be due to increased vulnerability of single eggs to low humidity conditions at necrotic leaf sites. We conclude that effectiveness of HR-like necrosis in B. nigra varies with plant genotype, plant individual and the type of egg laying behaviour (singly or clustered). By clustering eggs, cabbage white butterflies can escape the egg-killing, direct plant defence trait.
    Resisting the onset of herbivore attack : Plants perceive and respond to insect eggs
    Hilker, Monika ; Fatouros, Nina E. - \ 2016
    Current Opinion in Plant Biology 32 (2016). - ISSN 1369-5266 - p. 9 - 16.

    Plants can respond to attack by herbivorous insects very soon after herbivores start producing a new generation by depositing eggs onto their leaves. Egg-induced plant responses may result in killing the attacker in its egg stage. However, if the eggs do survive, they can also prime feeding-induced plant defenses against the larvae hatching from eggs. In this paper we focus first on egg-induced plant responses that resemble hypersensitive responses (HR) to phytopathogens and lead to egg desiccation or detachment from plants. We then summarize the current knowledge about egg-mediated effects on feeding-induced plant defenses against larvae. Finally, we discuss the insect species specificity of plant responses to eggs and the variability of insect susceptibility to these responses.

    Plant responses to insect egg deposition
    Hilker, M. ; Fatouros, N.E. - \ 2015
    Annual Review of Entomology 60 (2015). - ISSN 0066-4170 - p. 493 - 515.
    sogatella-furcifera horvath - elm leaf beetle - parasitoid anagrus-nilaparvatae - medfly ceratitis-capitata - oryza-sativa l. - defense responses - pieris-brassicae - host location - phytophagous insects - ovicidal substance
    Plants can respond to insect egg deposition and thus resist attack by herbivorous insects from the beginning of the attack, egg deposition. We review ecological effects of plant responses to insect eggs and differentiate between egg-induced plant defenses that directly harm the eggs and indirect defenses that involve egg parasitoids. Furthermore, we discuss the ability of plants to take insect eggs as warning signals; the eggs indicate future larval feeding damage and trigger plant changes that either directly impair larval performance or attract enemies of the larvae. We address the questions of how egg-associated cues elicit plant defenses, how the information that eggs have been laid is transmitted within a plant, and which molecular and chemical plant responses are induced by egg deposition. Finally, we highlight evolutionary aspects of the interactions between plants and insect eggs and ask how the herbivorous insect copes with egg-induced plant defenses and may avoid them by counteradaptations.
    Insect egg deposition induces indirect defense and epicuticular wax changes in Arabidopsis thaliana
    Blenn, B. ; Bandoly, M. ; Küffner, A. ; Otte, T. ; Geiselhardt, S. ; Fatouros, N.E. ; Hilker, M. - \ 2012
    Journal of Chemical Ecology 38 (2012)7. - ISSN 0098-0331 - p. 882 - 892.
    furcifera horvath homoptera - plant cuticular waxes - whitebacked planthopper - eceriferum mutants - trissolcus-basalis - pierid butterflies - nezara-viridula - host location - up-regulation - rice plants
    Egg deposition by the Large Cabbage White butterfly Pieris brassicae on Brussels sprouts plants induces indirect defense by changing the leaf surface, which arrests the egg parasitoid Trichogramma brassicae. Previous studies revealed that this indirect defense response is elicited by benzyl cyanide (BC), which is present in the female accessory reproductive gland (ARG) secretion and is released to the leaf during egg deposition. Here, we aimed (1) to elucidate whether P. brassicae eggs induce parasitoid-arresting leaf surface changes in another Brassicacean plant, i.e., Arabidopsis thaliana, and, if so, (2) to chemically characterize the egg-induced leaf surface changes. Egg deposition by P. brassicae on A. thaliana leaves had similar effects to egg deposition on Brussels sprouts with respect to the following: (a) Egg deposition induced leaf surface changes that arrested T. brassicae egg parasitoids. (b) Application of ARG secretion of mated female butterflies or of BC to leaves had the same inductive effects as egg deposition. Based on these results, we conducted GC-MS analysis of leaf surface compounds from egg- or ARG-induced A. thaliana leaves. We found significant quantitative differences in epicuticular waxes compared to control leaves. A discriminant analysis separated surface extracts of egg-laden, ARG-treated, untreated control and Ringer solution-treated control leaves according to their quantitative chemical composition. Quantities of the fatty acid tetratriacontanoic acid (C34) were significantly higher in extracts of leaf surfaces arresting the parasitoids (egg-laden or ARG-treated) than in respective controls. In contrast, the level of tetracosanoic acid (C24) was lower in extracts of egg-laden leaves compared to controls. Our study shows that insect egg deposition on a plant can significantly affect the quantitative leaf epicuticular wax composition. The ecological relevance of this finding is discussed with respect to its impact on the behavior of egg parasitoids.
    Anti-aphrodisiac compounds of male butterflies increase the risk of egg parasitoid attack by inducing plant synomone production
    Fatouros, N.E. ; Pashalidou, F.G. ; Aponte Cordero, W.V. ; Loon, J.J.A. van; Mumm, R. ; Dicke, M. ; Hilker, M. ; Huigens, M.E. - \ 2009
    Journal of Chemical Ecology 35 (2009)11. - ISSN 0098-0331 - p. 1373 - 1381.
    pieris-rapae - methyl salicylate - predatory mite - defense responses - pinus-sylvestris - cabbage white - host location - insect - volatiles - oviposition
    During mating in many butterfly species, males transfer spermatophores that contain anti-aphrodisiacs to females that repel conspecific males. For example, males of the large cabbage white, Pieris brassicae (Lepidoptera: Pieridae), transfer the anti-aphrodisiac, benzyl cyanide (BC) to females. Accessory reproductive gland (ARG) secretion of a mated female P. brassicae that is deposited with an egg clutch contains traces of BC, inducing Brussels sprouts plants (Brassica oleracea var. gemmifera) to arrest certain Trichogramma egg parasitoids. Here, we assessed whether deposition of one egg at a time by the closely related small cabbage white, Pieris rapae, induced B. oleracea var. gemmifera to arrest Trichogramma wasps, and whether this plant synomone is triggered by substances originating from male P. rapae seminal fluid. We showed that plants induced by singly laid eggs of P. rapae arrest T. brassicae wasps three days after butterfly egg deposition. Elicitor activity was present in ARG secretion of mated female butterflies, whereas the secretion of virgin females was inactive. Pieris rapae used a mixture of methyl salicylate (MeSA) and indole as an anti-aphrodisiac. We detected traces of both anti-aphrodisiacal compounds in the ARG secretion of mated female P. rapae, whereas indole was lacking in the secretion of virgin female P. rapae. When applied onto the leaf, indole induced changes in the foliar chemistry that arrested T. brassicae wasps. This study shows that compounds of male seminal fluid incur possible fitness costs for Pieris butterflies by indirectly promoting egg parasitoid attack
    Foraging behavior of egg parasitoids exploiting chemical information
    Fatouros, N.E. ; Dicke, M. ; Mumm, R. ; Meiners, T. ; Hilker, M. - \ 2008
    Behavioral Ecology 19 (2008)3. - ISSN 1045-2249 - p. 677 - 689.
    trichogramma-evanescens hymenoptera - telenomus-euproctidis hymenoptera - australis fabricius heteroptera - podisus-maculiventris hemiptera - trissolcus-basalis hymenoptera - heliothis-zea lepidoptera - european corn-borer - pieris-brassicae l - footed plant bug
    Female parasitic wasps seek hosts for their offspring often in a dynamic environment. Foraging egg parasitoids rely on a variety of chemical cues originating from the adult host, host products, or the host plant rather than from the attacked host stage¿the insect egg itself. Besides pupae, insect eggs are the most inconspicuous host stage attacked by parasitic wasps. To overcome the problem of low detectability of host eggs, egg parasitoids have evolved several strategies such as exploiting long-range kairomones of the adult hosts, for example, host aggregation and sex pheromones, plant synomones induced by egg deposition or host feeding, or short-range contact cues derived from the adult host or the host plant. Moreover, egg parasitoids have evolved the ability to use chemical espionage in combination with hitchhiking on the adult host (phoresy) to compensate their limited flight capability and to gain access to freshly laid host eggs. Here, we provide a comprehensive overview on the variety of host-foraging strategies of egg parasitoids exploiting chemical signals. Furthermore, the use of such infochemicals is discussed with respect to the wasps¿ dietary breadth and their ability to learn
    Male-derived butterfly anti-aphrodisiac mediates induced indirect plant defense
    Fatouros, N.E. ; Broekgaarden, C. ; Bukovinszkine-Kiss, G. ; Loon, J.J.A. van; Mumm, R. ; Huigens, M.E. ; Dicke, M. ; Hilker, M. - \ 2008
    Proceedings of the National Academy of Sciences of the United States of America 105 (2008). - ISSN 0027-8424 - p. 10033 - 10038.
    parasitic wasps - pierid butterflies - oral secretions - gene-expression - host location - atp synthase - insect - elicitors - volatiles - oviposition
    Plants can recruit parasitic wasps in response to egg deposition by herbivorous insects¿a sophisticated indirect plant defense mechanism. Oviposition by the Large Cabbage White butterfly Pieris brassicae on Brussels sprout plants induces phytochemical changes that arrest the egg parasitoid Trichogramma brassicae. Here, we report the identification of an elicitor of such an ovipositioninduced plant response. Eliciting activity was present in accessory gland secretions released by mated female butterflies during egg deposition. In contrast, gland secretions from virgin female butterflies were inactive. In the male ejaculate, P. brassicae females receive the anti-aphrodisiac benzyl cyanide (BC) that reduces the females¿ attractiveness for subsequent mating. We detected this pheromone in the accessory gland secretion released by mated female butterflies. When applied onto leaves, BC alone induced phytochemical changes that arrested females of the egg parasitoid. Microarray analyses revealed a similarity in induced plant responses that may explain the arrest of T. brassicae to egg-laden and BC-treated plants. Thus, a male-derived compound endangers the offspring of the butterfly by inducing plant defense. Recently, BC was shown to play a role in foraging behavior of T. brassicae, by acting as a cue to facilitate phoretic transport by mated female butterflies to oviposition sites. Our results suggest that the antiaphrodisiac pheromone incurs fitness costs for the butterfly by both mediating phoretic behavior and inducing plant defense.
    The role of comptetitors for Chrysomela lapponica, a north Eurasian willow pest, in pioneering a new host plant
    Gross, J. ; Fatouros, N.E. ; Neuvonen, S. ; Hilker, M. - \ 2007
    Journal of Pest Science 80 (2007)3. - ISSN 1612-4758 - p. 139 - 143.
    defensive secretion - leaf beetles - coleoptera - insects - specialization - performance - quality - europe - larvae
    The Palaearctic leaf beetle Chrysomela lapponica usually feeds upon willows in the northern region of its occurrence. However, in Central Europe, some populations are known that have specialised on birch. In this study, we investigated the significance of other herbivores occurring together on the same host plants as possible exploitative competitors of C. lapponica. Two populations were studied: a population from Finland specialised on the willow Salix borealis, and a population from the Czech Republic, specialised on the birch Betula pubescens. Abundances of folivorous and suctivorous insects on both host plants were recorded at both population sites. The willow leaf beetle Phratora vitellinae was the most abundant herbivorous insect at both study sites on willow. A field study was conducted to examine the effects of P. vitellinae on the performance of C. lapponica. The presence of P. vitellinae larvae on the same twig upon which C. lapponica larvae were feeding did not affect increase of body weight in C. lapponica larvae. Thus, the high resource availability of both willows and birches suggest that interspecific competition is unlikely to be a selection factor driving the evolution of host shift in C. lapponica.
    The response specificity of Trichogramma egg parasitoids towards infochemicals during host location
    Fatouros, N.E. ; Bukovinszkine-Kiss, G. ; Dicke, M. ; Hilker, M. - \ 2007
    Journal of Insect Behavior 20 (2007)1. - ISSN 0892-7553 - p. 53 - 65.
    pieris-brassicae l - evanescens westwood - behavioral variations - mamestra-brassicae - biological-control - strains - hymenoptera - oviposition - lepidoptera - kairomones
    Parasitoids are confronted with many different infochemicals of their hosts and food plants during host selection. Here, we investigated the effect of kairomones from the adult host Pieris brassicae and of cues present on Brussels sprout plants infested by P. brassicae eggs on the behavioral response of the egg parasitoid Trichogramma evanescens. Additionally, we tested whether the parasitoid¿s acceptance of P. brassicae eggs changes with different host ages. The wasps did not discriminate between olfactory cues from mated and virgin females or between mated females and males of P. brassicae. T. evanescens randomly climbed on the butterflies, showing a phoretic behavior without any preference for a certain sex. The parasitoid was arrested on leaf parts next to 1-day-old host egg masses. This arrestment might be due to cues deposited during oviposition. The wasps parasitized host eggs up to 3 days old equally well. Our results were compared with former studies on responses by T .brassicae showing that T. evanescens makes less use of infochemicals from P. brassicae than T. brassicae.
    Direct and indirect chemical defence of pine against folivorous insects
    Mumm, R. ; Hilker, M. - \ 2006
    Trends in Plant Science 11 (2006)7. - ISSN 1360-1385 - p. 351 - 358.
    dependent pheromone responses - spruce budworm defoliation - sawfly diprion-pini - scots pine - bark beetles - lodgepole pine - egg deposition - douglas-fir - natural defoliation - volatile emissions
    The chemical defence of pine against herbivorous insects has been intensively studied with respect to its effects on the performance and behaviour of the herbivores as well as on the natural enemies of pine herbivores. The huge variety of terpenoid pine components play a major role in mediating numerous specific food web interactions. The constitutive terpenoid pattern can be adjusted to herbivore attack by changes induced by insect feeding or oviposition activity. Recent studies on folivorous pine sawflies have highlighted the role of induced pine responses in herbivore attack and have demonstrated the importance of analysing the variability of pine defence and its finely tuned specificity with respect to the herbivore attacker in a multitrophic context.
    Reproductive isolation between populations from Northern and Central Europe of the leaf beetle Chrysomela lapponica L.
    Fatouros, N.E. ; Hilker, M. ; Gross, J. - \ 2006
    Chemoecology 16 (2006)4. - ISSN 0937-7409 - p. 241 - 251.
    phratora-vitellinae coleoptera - insect plant interactions - host-plant - galerucella-nymphaeae - defensive secretion - chemical defense - antimicrobial activity - chemotaxonomic survey - adalia-bipunctata - life-history
    Allopatric populations of the leaf beetle Chrysomela lapponica are known to feed upon either willow (Salicaceae) or birch (Betulaceae). This study aimed to elucidate the differentiation process of these allopatric populations. We investigated whether these allopatric populations specialized on different host plants are still able to produce fertile offspring when interbreeding. Individuals from a population in Finland (willow specialists) and one in the Czech Republic (birch specialists) were crossed in laboratory. Hybrid formation succeeded only between females from the Czech, birch specialized population and males from the Finnish, willow specialized population, while no eggs were produced by females of the willow specialists having mated males of the birch specialists. Behavioral, morphological, physiological, and chemical features of the F1 hybrids were studied. The chemical composition of larval defensive secretion and feeding preferences of the resulting F1 hybrids mainly showed similarities with the paternal phenotype, while the area of black coloring on the offspring¿s elytra was intermediate between those of the parental elytra. F1 hybrids did not accept the host plant (birch) of their mothers for feeding and only survived on willow. Thus, since mothers only lay eggs on birch, we found evidence for a postzygotic isolation mechanism between the individuals of the two investigated populations: when having been mated with willow specialized Finnish males, the birch specialized Czech mothers place the hybrid eggs on a plant species (birch), on which the hatching larvae cannot survive.
    The significance of background odour for an egg parasitoid to detect plants with host eggs
    Mumm, R. ; Hilker, M. - \ 2005
    Chemical Senses 30 (2005)4. - ISSN 0379-864X - p. 337 - 343.
    achromatic cues - phytoseiulus-persimilis - olfactory responses - volatile emissions - insect herbivores - colored patterns - pinus-sylvestris - alarm pheromone - cotton plants - bark beetles
    Scots pine has been shown to produce a volatile bouquet that attracts egg parasitoids in response to oviposition of the herbivorous sawfly Diprion pini. Previous analyses of headspace volatiles of oviposition-induced pine twigs revealed only quantitative changes; in particular, the sesquiterpene (E)-ß-farnesene was emitted in significantly higher quantities by oviposition-induced pine. Here we investigated whether (E)-ß-farnesene attracted the egg parasitoid Chrysonotomyia ruforum. We tested the behavioural response of C. ruforum females to different concentrations of (E)-ß-farnesene. Egg parasitoids did not respond to this sesquiterpene at either concentration tested. However, they did respond significantly to (E)-ß-farnesene when this compound was offered in combination with the volatile blend emitted from pine twigs without eggs. This response was dependent on the applied concentration of (E)-ß-farnesene. Further bioassays with other components [(E)-ß-caryophyllene, -cadinene] of the odour blend of pine were conducted in combination with the volatile blend from egg-free pine as background odour. None of the compounds tested against the background of odour from an egg-free pine twig were attractive to the egg parasitoid. These results suggest that the egg parasitoids responded specifically to (E)-ß-farnesene, but only when this compound was experienced in the `right` context, i.e. when contrasted with a background odour of non-oviposition-induced pine volatiles
    Induction of terpenoid pine volatiles by insect egg deposition: analysis of volatiles and tritrophic interactions
    Mumm, R. ; Hilker, M. - \ 2005
    Choosy egg parasitoids: specificity of oviposition-induced pine volatiles exploited by an egg parasitoid of pine sawflies
    Mumm, R. ; Tiemann, T. ; Varama, M. ; Hilker, M. - \ 2005
    Entomologia Experimentalis et Applicata 115 (2005)1. - ISSN 0013-8703 - p. 217 - 225.
    plant-carnivore mutualism - diprion-pini - dietary specialization - infochemical use - natural enemies - apis-mellifera - complex odors - host location - genus pinus - black pine
    Generalist parasitoids are well-known to be able to cope with the high genotypic and phenotypic plasticity of plant volatiles by learning odours during their host encounters. In contrast, specialised parasitoids often respond innately to host-specific cues. Previous studies have shown that females of the specialised egg parasitoid Chrysonotomyia ruforum Krausse (Hymenoptera: Eulophidae) are attracted to volatiles from Pinus sylvestris L. induced by the egg deposition of its host Diprion pini L. (Hymenoptera: Diprionidae), when they have previously experienced pine twigs with host eggs. In this study we investigated by olfactometer bioassays how specifically C. ruforum responded to oviposition-induced plant volatiles. Furthermore, we studied whether parasitoids show an innate response to oviposition-induced pine volatiles. Naïve parasitoids were not attracted to oviposition-induced pine volatiles. The attractiveness of volatiles from pines carrying eggs was shown to be specific for the pine and herbivore species, respectively (species specificity). We also tested whether not only oviposition, but also larval feeding, induces attractive volatiles (developmental stage specificity). The feeding of D. pini larvae did not induce the emission of P. sylvestris volatiles attractive to the egg parasitoid. Our results show that a specialist egg parasitoid does not innately show a positive response to oviposition-induced plant volatiles, but needs to learn them. Furthermore, the results show that C. ruforum as a specialist does not learn a wide range of volatiles as some generalists do, but instead learns only a very specific oviposition-induced plant volatile pattern, i.e., a pattern induced by the most preferred host species laying eggs on the most preferred food plant
    Oviposition-induced plant cues: do they arrest Trichogramma wasps during host location?
    Fatouros, N.E. ; Bukovinszkine-Kiss, G. ; Kalkers, L.A. ; Soler Gamborena, R. ; Dicke, M. ; Hilker, M. - \ 2005
    Entomologia Experimentalis et Applicata 115 (2005)1. - ISSN 0013-8703 - p. 207 - 215.
    pieris-brassicae - carnivorous arthropods - insect oviposition - pinus-sylvestris - infochemical use - natural enemies - egg parasitoids - sex-pheromone - tussock moth - volatiles
    Plants can defend themselves against herbivorous insects before the larvae hatch from eggs and start feeding. One of these preventive defence strategies is to produce plant volatiles, in response to egg deposition, which attract egg parasitoids that subsequently kill the herbivore eggs. Here, we studied whether egg deposition by Pieris brassicae L. (Lepidoptera: Pieridae) induces Brussels sprouts plants to produce cues that attract or arrest Trichogramma brassicae Bezdeko (Hymenoptera: Trichogrammatidae). Olfactometer bioassays revealed that odours from plants with eggs did not attract or arrest parasitoids. However, contact bioassays showed that T. brassicae females were arrested on egg-free leaf squares excised from leaves with 72 h-old egg masses, which are highly suitable for parasitisation. We tested the hypothesis that this arresting activity is due to scales and chemicals deposited by the butterflies during oviposition and which are thus present on the leaf surface in the vicinity of the eggs. Indeed, leaf squares excised from egg-free leaves, but contaminated with butterfly deposits, arrested the wasps when the squares were tested 1 day after contamination. However, squares from egg-free leaves with 72 h-old butterfly deposits had no arresting activity. Thus, we exclude that the arresting activity of the leaf area near 72 h-old egg masses was elicited by cues from scales and other butterfly deposits. We suggest that egg deposition of P. brassicae induces a change in the leaf surface chemicals in leaves with egg masses. A systemic induction extending to an egg-free leaf neighbouring an egg-carrying leaf could not be detected. Our data suggest that a local, oviposition-induced change of leaf surface chemicals arrests T. brassicae in the vicinity of host eggs
    Editorial: Butterfly anti-aphrodisiac lures parasitic wasps
    Fatouros, N.E. ; Huigens, M.E. ; Loon, J.J.A. van; Dicke, M. ; Hilker, M. - \ 2005
    Nature 433 (2005)7027. - ISSN 0028-0836 - p. 704 - 704.
    scelionidae - hymenoptera
    To locate their hosts, parasitic wasps can 'eavesdrop' on the intraspecific chemical communications of their insect hosts1, 2, 3. Here we describe an example in which the information exploited by the parasitic wasp Trichogramma brassicae is a butterfly anti-aphrodisiac that is passed from male to female Pieris brassicae butterflies during mating, to render them less attractive to conspecific males4, 5, 6. When the tiny wasp detects the odour of a mated female butterfly, it rides on her (Fig. 1) to her egg-laying sites and then parasitizes the freshly laid eggs. If this fascinating strategy is widespread in nature, it could severely constrain the evolution of sexual communication between hosts.
    Induced plant responses towards herbivory
    Hilker, M. ; Dicke, M. - \ 2003
    Basic and Applied Ecology 4 (2003)1. - ISSN 1439-1791 - p. 1 - 2.
    Induced plant defences : from molecular biology to evolutionary ecology
    Dicke, M. ; Hilker, M. - \ 2003
    Basic and Applied Ecology 4 (2003)1. - ISSN 1439-1791 - p. 3 - 14.
    bottom-up forces - herbivore-induced volatiles - jasmonate-induced responses - manduca-sexta lepidoptera - host nicotiana-attenuata - arabidopsis-thaliana - top-down - gene-expression - induced resistance - beta-glucosidase
    Phenotypic plasticity enables invididuals to change their phenotype in response to their environment. These phenotypic changes can affect many interactions between the members of a community. Plants are able to respond towards herbivore attack by defensive mechanisms directly affecting the herbivore and by so-called indirect defences that negatively affect the herbivore by maintenance or attraction of carnivores. The phenotypic changes of plants caused by induced defences may vary with the type of attackers. Different attackers can evoke different plant responses due to specific elicitors or wounding. These different plant responses may be mediated by different choreographies of gene expression. Symbiotic and pathogenic microorganisms associated with the plant or the herbivore may play an important role in the induction process. Thus, a plethora of biotic factors affect the physiological, chemical, and molecular characteristics of plants in response to attack. The adaptiveness of phenotypic plasticity in terms of induced responses depends on the balance of their physiological and ecological costs and benefits. An integrated approach is necessary considering ecological, molecular and chemical aspects to gain deeper insight into induced defence and its application in environmentally benign crop protection.
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