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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    To be in time: egg deposition enhances plant-mediated detection of young caterpillars by parasitoids
    Pashalidou, F.G. ; Gols, R. ; Berkhout, B.W. ; Weldegergis, B.T. ; Loon, J.J.A. van; Dicke, M. ; Fatouros, N.E. - \ 2015
    Oecologia 177 (2015)2. - ISSN 0029-8549 - p. 477 - 486.
    different larval instars - pieris-brassicae - specialist herbivore - volatile emissions - cotesia-glomerata - host location - oviposition - responses - maize - generalist
    Animals use information from their environment while foraging for food or prey. When parasitic wasps forage for hosts, they use plant volatiles induced by herbivore activities such as feeding and oviposition. Little information is available on how wasps exploit specific plant volatiles over time, and which compounds indicate changes in host quality. In experiments investigating the role of herbivore-induced plant volatiles in wasp foraging, induction of plant response is usually achieved by placing larvae on clean plants instead of allowing the natural sequence of events: to let eggs deposited by the herbivore develop into larvae. We compared the attraction of the parasitoid Cotesia glomerata to volatiles emitted by black mustard (Brassica nigra) plants induced by eggs and successive larval stages of the Large Cabbage White butterfly (Pieris brassicae) to the attraction of this parasitoid to black mustard plant volatiles induced only by larval feeding in a wind tunnel setup. We show that wasps are attracted to plants infested with eggs just before and shortly after larval hatching. However, wasp preference changed at later time points towards plants induced only by larval feeding. These temporal changes in parasitoid attraction matched with changes in the chemical compositions of the blends of plant volatiles. Previous studies have shown that host quality/suitability decreases with caterpillar age and that P. brassicae oviposition induces plant defences that negatively affect subsequently feeding caterpillars. We investigated parasitoid performance in hosts of different ages. Wasp performance was positively correlated with preference. Moreover, parasitism success decreased with time and host stage. In conclusion, the behaviour of Cotesia glomerata is fine-tuned to exploit volatiles induced by eggs and early host stages that benefit parasitoid fitness.
    Variation in plant defences among populations of a range-expanding plant: consequences for trophic interactions
    Fortuna, T.M. ; Eckert, S. ; Harvey, J.A. ; Vet, L.E.M. ; Müller, C. ; Gols, R. - \ 2014
    New Phytologist 204 (2014)4. - ISSN 0028-646X - p. 989 - 999.
    increased competitive ability - bunias orientalis l - invasive plant - insect herbivores - secondary metabolites - specialist herbivore - alliaria-petiolata - chemical defense - native insect - host
    Although plant-herbivore-enemy interactions have been studied extensively in cross-continental plant invasions, little is known about intra-continental range expanders, despite their rapid spread globally. Using an ecological and metabolomics approach, we compared the insect performance of a generalist and specialist herbivore and a parasitoid, as well as plant defence traits, among native, exotic invasive and exotic non-invasive populations of the Turkish rocket, Bunias orientalis, a range-expanding species across parts of Eurasia. In the glasshouse, the generalist herbivore, Mamestra brassicae, and its parasitoid, Microplitis mediator, performed better on non-native than on native plant populations. Insect performance did not differ between the two non-native origins. By contrast, the specialist herbivore, Pieris brassicae, developed poorly on all populations. Differences in trichome densities and in the metabolome, particularly in the family-specific secondary metabolites (i.e. glucosinolates), may explain population-related variation in the performance of the generalist herbivore and its parasitoid. Total glucosinolate concentrations were significantly induced by herbivory, particularly in native populations. Native populations of B. orientalis are generally better defended than non-native populations. The role of insect herbivores and dietary specialization as a selection force on defence traits in the range-expanding B. orientalis is discussed.
    Sequential effects of root and foliar herbivory on aboveground and belowground induced plant defense responses and insect performance
    Wang, M. ; Biere, A. ; Putten, W.H. van der; Bezemer, T.M. - \ 2014
    Oecologia 175 (2014)1. - ISSN 0029-8549 - p. 187 - 198.
    deterrent iridoid glycosides - mediated interactions - specialist herbivore - chemical defense - lanceolata l - induction - generalist - damage - age - chemistry
    Plants are often simultaneously or sequentially attacked by multiple herbivores and changes in host plants induced by one herbivore can influence the performance of other herbivores. We examined how sequential feeding on the plant Plantago lanceolata by the aboveground herbivore Spodoptera exigua and the belowground herbivore Agriotes lineatus influences plant defense and the performance of both insects. Belowground herbivory caused a reduction in the food consumption by the aboveground herbivore independent of whether it was initiated before, at the same time, or after that of the aboveground herbivore. By contrast, aboveground herbivory did not significantly affect belowground herbivore performance, but significantly reduced the performance of later arriving aboveground conspecifics. Interestingly, belowground herbivores negated negative effects of aboveground herbivores on consumption efficiency of their later arriving conspecifics, but only if the belowground herbivores were introduced simultaneously with the early arriving aboveground herbivores. Aboveground–belowground interactions could only partly be explained by induced changes in an important class of defense compounds, iridoid glycosides (IGs). Belowground herbivory caused a reduction in IGs in roots without affecting shoot levels, while aboveground herbivory increased IG levels in roots in the short term (4 days) but only in the shoots in the longer term (17 days). We conclude that the sequence of aboveground and belowground herbivory is important in interactions between aboveground and belowground herbivores and that knowledge on the timing of exposure is essential to predict outcomes of aboveground–belowground interactions.
    Development of a generalist predator, Podisus maculiventris, on glucosinolate sequestering and nonsequestering prey
    Geem, M. van; Harvey, J.A. ; Gols, R. - \ 2014
    Naturwissenschaften 101 (2014)9. - ISSN 0028-1042 - p. 707 - 714.
    sawfly athalia-rosae - plant-chemical defense - pyrrolizidine alkaloids - insect herbivore - multitrophic interactions - specialist herbivore - trophic levels - trade-offs - sequestration - host
    Insect herbivores exhibit various strategies to counter the toxic effects of plant chemical defenses. These strategies include the detoxification, excretion, and sequestration of plant secondary metabolites. The latter strategy is often considered to provide an additional benefit in that it provides herbivores with protection against natural enemies such as predators. Profiles of sequestered chemicals are influenced by the food plants from which these chemicals are derived. We compared the effects of sequestration and nonsequestration of plant secondary metabolites in two specialist herbivores on the development of a generalist predator, Podisus maculiventris. Profiles of glucosinolates, secondary metabolites characteristic for the Brassicaceae, are known to differ considerably both inter- and intraspecifically. Throughout their immature (=nymphal) development, the predator was fed on larval stages of either sequestering (turnip sawfly, Athalia rosae) or nonsequestering (small cabbage white butterfly, Pieris rapae) prey that in turn had been feeding on plants originating from three wild cabbage (Brassica oleracea) populations that have previously been shown to differ in their glucosinolate profiles. We compared survival, development time, and adult body mass as parameters for bug performance. Our results show that sequestration of glucosinolates by A. rosae only marginally affected the development of P. maculiventris. The effects of plant population on predator performance were variable. We suggest that sequestration of glucosinolates by A. rosae functions not only as a defensive mechanism against some predators, but may also be an alternative way of harmlessly dealing with plant allelochemicals.
    Direct and indirect chemical defences against insects in a multitrophic framework
    Gols, R. - \ 2014
    Plant, Cell & Environment 37 (2014)8. - ISSN 0140-7791 - p. 1741 - 1752.
    induced plant volatiles - natural enemy interactions - high-mortality hypothesis - 4 trophic levels - host-plant - lepidopteran herbivores - specialist herbivore - mycorrhizal fungi - brassica-oleracea - slow-growth
    Plant secondary metabolites play an important role in mediating interactions with insect herbivores and their natural enemies. Metabolites stored in plant tissues are usually investigated in relation to herbivore behaviour and performance (direct defence), whereas volatile metabolites are often studied in relation to natural enemy attraction (indirect defence). However, so-called direct and indirect defences may also affect the behaviour and performance of the herbivore's natural enemies and the natural enemy's prey or hosts, respectively. This suggests that the distinction between these defence strategies may not be as black and white as is often portrayed in the literature. The ecological costs associated with direct and indirect chemical defence are often poorly understood. Chemical defence traits are often studied in two-species interactions in highly simplified experiments. However, in nature, plants and insects are often engaged in mutualistic interactions with microbes that may also affect plant secondary chemistry. Moreover, plants are challenged by threats above- and belowground and herbivory may have consequences for plant-insect multitrophic interactions in the alternative compartment mediated by changes in plant secondary chemistry. These additional associations further increase the complexity of interaction networks. Consequently, the effect of a putative defence trait may be under- or overestimated when other interactions are not considered.
    Reciprocal crosstalk between jasmonate and salicylate defence-signalling pathways modulates plant volatile emission and herbivore host-selection behaviour
    Wei, J. ; Loon, J.J.A. van; Gols, R. ; Menzel, T.R. ; Li, N. ; Kang, L. ; Dicke, M. - \ 2014
    Journal of Experimental Botany 65 (2014)12. - ISSN 0022-0957 - p. 3289 - 3298.
    mediated interactions - specialist herbivore - tetranychus-urticae - induced resistance - parasitic wasps - cotton plants - spider-mites - insect - acid - pathogen
    The jasmonic acid (JA) and salicylic acid (SA) signalling pathways, which mediate induced plant defence responses, can express negative crosstalk. Limited knowledge is available on the effects of this crosstalk on host-plant selection behaviour of herbivores. We report on temporal and dosage effects of such crosstalk on host preference and oviposition-site selection behaviour of the herbivorous spider mite Tetranychus urticae towards Lima bean (Phaseolus lunatus) plants, including underlying mechanisms. Behavioural observations reveal a dynamic temporal response of mites to single or combined applications of JA and SA to the plant, including attraction and repellence, and an antagonistic interaction between SA- and JA-mediated plant responses. Dose-response experiments show that concentrations of 0.001mM and higher of one phytohormone can neutralize the repellent effect of a 1mM application of the other phytohormone on herbivore behaviour. Moreover, antagonism between the two signal-transduction pathways affects phytohormone-induced volatile emission. Our multidisciplinary study reveals the dynamic plant phenotype that is modulated by subtle changes in relative phytohormonal titres and consequences for the dynamic host-plant selection by an herbivore. The longer-term effects on plant–herbivore interactions deserve further investigation.
    Seasonal phenology of interactions involving short-lived annual plants, a multivoltine herbivore and its endoparasitoid wasp
    Fei, M. ; Gols, R. ; Harvey, J.A. - \ 2014
    Journal of Animal Ecology 83 (2014)1. - ISSN 0021-8790 - p. 234 - 244.
    specialist herbivore - brassica-oleracea - trophic levels - quality - evolution - sequestration - consequences - constraints - parasitoids - coleoptera
    Spatial-temporal realism is often missing in many studies of multitrophic interactions, which are conducted at a single time frame and/or involving interactions between insects with a single species of plant. In this scenario, an underlying assumption is that the host-plant species is ubiquitous throughout the season and that the insects always interact with it. We studied interactions involving three naturally occurring wild species of cruciferous plants, Brassica rapa, Sinapis arvensis and Brassica nigra, that exhibit different seasonal phenologies, and a multivoltine herbivore, the large cabbage white butterfly, Pieris brassicae, and its gregarious endoparasitoid wasp, Cotesia glomerata. The three plants have very short life cycles. In central Europe, B. rapa grows in early spring, S. arvensis in late spring and early summer, and B. nigra in mid to late summer. P. brassicae generally has three generations per year, and C. glomerata at least two. This means that different generations of the insects must find and exploit different plant species that may differ in quality and which may be found some distance from one another. Insects were either reared on each of the three plant species for three successive generations or shifted between generations from B. rapa to S. arvensis to B. nigra. Development time from neonate to pupation and pupal fresh mass were determined in P. brassicae and egg-to-adult development time and body mass in C. glomerata. Overall, herbivores performed marginally better on S. arvensis and B. nigra plants than on B. rapa plants. Parasitoids performance was closely tailored with that of the host. Irrespective as to whether the insects were shifted to a new plant in successive generations or not, development time of P. brassicae and C. glomerata decreased dramatically over time. Our results show that there were some differences in insect development on different plant species and when transferred from one species to another. However, all three plants were of generally high quality in terms of insect performance. We discuss ecological and evolutionary constraints on insects that must search in new habitats for different plant species over successive generations.
    A tritrophic approach to the preference-performance hypothesis involving an exotic and a native plant
    Fortuna, T.F.M. ; Woelke, J.B. ; Hordijk, C.A. ; Jansen, J.J. ; Dam, N.M. van; Vet, L.E.M. ; Harvey, J.A. - \ 2013
    Biological Invasions 15 (2013)11. - ISSN 1387-3547 - p. 2387 - 2401.
    parasitoids cotesia-glomerata - phytophagous insects - oviposition preference - invasive plant - c-rubecula - specialist herbivore - bunias orientalis - natural enemies - host - butterflies
    Exotic plants often generate physical and chemical changes in native plant communities where they become established. A major challenge is to understand how novel plants may affect trophic interactions in their new habitats, and how native herbivores and their natural enemies might respond to them. We compared the oviposition preference and offspring performance of the crucifer specialist, Pieris brassicae, on an exotic plant, Bunias orientalis, and on a related native plant, Sinapis arvensis. Additionally, we studied the response of the parasitoid, Cotesia glomerata to herbivore-induced plant volatiles (HIPV) and determined the volatile blend composition to elucidate which compound(s) might be involved in parasitoid attraction. On both host plants we also compared the parasitism rate of P. brassicae by C. glomerata. Female butterflies preferred to oviposit on the native plant and their offspring survival and performance was higher on the native plant compared to the exotic. Although, headspace analysis revealed qualitative and quantitative differences in the volatile blends of both plant species, C. glomerata did not discriminate between the HIPV blends in flight-tent bioassays. Nevertheless, parasitism rate of P. brassicae larvae was higher on the native plant under semi-field conditions. Overall, P. brassicae oviposition preference may be more influenced by bottom-up effects of the host plant on larval performance than by top-down pressure exerted by its parasitoid. The potential for dietary breadth expansion of P. brassicae to include the exotic B. orientalis and the role of top-down processes played by parasitoids in shaping herbivore host shifts are further discussed
    Pyrrolizidine Alkaloid Composition Influences Cinnabar Moth Oviposition Preferences in Jacobaea Hybrids
    Cheng, D. ; Meijden, E. van der; Mulder, P.P.J. ; Vrieling, K. ; Klinkhamer, P.G.L. - \ 2013
    Journal of Chemical Ecology 39 (2013)3. - ISSN 0098-0331 - p. 430 - 437.
    host-plant choice - senecio-jacobaea - specialist herbivore - generalist herbivores - tyria-jacobaeae - chemical defense - evolution - hybridization - populations - performance
    Plants produce a variety of secondary metabolites (PSMs) that may be selective against herbivores. Yet, specialist herbivores may use PSMs as cues for host recognition, oviposition, and feeding stimulation, or for their own defense against parasites and predators. This summarizes a dual role of PSMs: deter generalists but attract specialists. It is not clear yet whether specialist herbivores are a selective force in the evolution of PSM diversity. A prerequisite for such a selective force would be that the preference and/or performance of specialists is influenced by PSMs. To investigate these questions, we conducted an oviposition experiment with cinnabar moths (Tyria jacobaeae) and plants from an artificial hybrid family of Jacobaea vulgaris and Jacobaea aquatica. The cinnabar moth is a specialist herbivore of J. vulgaris and is adapted to pyrrolizidine alkaloids (PAs), defensive PSMs of these plants. The number of eggs and egg batches oviposited by the moths were dependent on plant genotype and positively correlated to concentrations of tertiary amines of jacobine-like PAs and some otosenine-like PAs. The other PAs did not correlate with oviposition preference. Results suggest that host plant PAs influence cinnabar moth oviposition preference, and that this insect is a potential selective factor against a high concentration of some individual PAs, especially those that are also involved in resistance against generalist herbivores
    Effects of an invasive plant on the performance of two parasitoids with different host exploitation strategies
    Fortuna, T.F.M. ; Vet, L.E.M. ; Harvey, J.A. - \ 2012
    Biological Control 62 (2012)3. - ISSN 1049-9644 - p. 213 - 220.
    enemy release hypothesis - insect herbivores - bunias-orientalis - natural enemies - reproductive strategies - specialist herbivore - native plant - ecology - quality - growth
    In their new range, exotic plants create the possibility for novel interactions to occur with native consumers. Whereas there is evidence that these novel interactions can be negative for native insects, alien plants that are closely related to native species may in fact act as important food sources for native insects during the growing season. Thus far, studies with invasive plants have mostly focused on plant–herbivore interactions. However, to better understand how top-down and bottom-up processes may affect the success of potential invaders we also need to consider the effects of invasive plants on higher trophic levels. We examine multitrophic interactions on an exotic invasive crucifer, Bunias orientalis, and a native crucifer, Brassica nigra. The performance of a specialist herbivore, Pieris brassicae, and two of its gregarious endoparasitoids, the koinobiont Cotesia glomerata and the idiobiont Pteromalus puparum, was investigated. Emphasis was laid on parasitoid host-resource use strategies and how these may be differently affected by the quality of the exotic food plant. P. brassicae larvae performed poorly on the exotic plant, with lower survival, longer development time and a lower pupal mass, than on the native plant. The exotic plant affected the performance of the two parasitoid species in different ways. C. glomerata survival was strongly co-ordinated with the survival of its larval host, showing also high mortality. Adult wasps that survived on Bu. orientalis had an extended development time and small body size. By contrast, Pt. puparum survival was similar on pupal hosts reared on both plant species. Our results show that constraints imposed by differing plant quality of native and exotic plants on trophic interactions can depend on resource use strategies of the species involved, suggesting that effects of exotic species should be elucidated on a case-by-case basis.
    Population-Related Variation in Plant Defense more Strongly Affects Survival of an Herbivore than Its Solitary Parasitoid Wasp
    Harvey, J.A. ; Gols, R. - \ 2011
    Journal of Chemical Ecology 37 (2011)10. - ISSN 0098-0331 - p. 1081 - 1090.
    hyperparasitoid performance - lepidopteran herbivores - campoletis-sonorensis - specialist herbivore - mortality hypothesis - insect parasitoids - brassica-oleracea - trichoplusia-ni - pieris-rapae - host-plant
    The performance of natural enemies, such as parasitoid wasps, is affected by differences in the quality of the host’s diet, frequently mediated by species or population-related differences in plant allelochemistry. Here, we compared survival, development time, and body mass in a generalist herbivore, the cabbage moth, Mamestra brassicae, and its solitary endoparasitoid, Microplitis mediator, when reared on two cultivated (CYR and STH) and three wild (KIM, OH, and WIN) populations of cabbage, Brassica oleracea. Plants either were undamaged or induced by feeding of larvae of the cabbage butterfly, Pieris rapae. Development and biomass of M. brassicae and Mi. mediator were similar on both cultivated and one wild cabbage population (KIM), intermediate on the OH population, and significantly lower on the WIN population. Moreover, development was prolonged and biomass was reduced on herbivore-induced plants. However, only the survival of parasitized hosts (and not that of healthy larvae) was affected by induction. Analysis of glucosinolates in leaves of the cabbages revealed higher levels in the wild populations than cultivars, with the highest concentrations in WIN plants. Multivariate statistics revealed a negative correlation between insect performance and total levels of glucosinolates (GS) and levels of 3-butenyl GS. However, GS chemistry could not explain the reduced performance on induced plants since only indole GS concentrations increased in response to herbivory, which did not affect insect performance based on multivariate statistics. This result suggests that, in addition to aliphatic GS, other non-GS chemicals are responsible for the decline in insect performance, and that these chemicals affect the parasitoid more strongly than the host. Remarkably, when developing on WIN plants, the survival of Mi. mediator to adult eclosion was much higher than in its host, M. brassicae. This may be due to the fact that hosts parasitized by Mi. mediator pass through fewer instars, and host growth is arrested when they are only a fraction of the size of healthy caterpillars. Certain aspects of the biology and life-history of the host and parasitoid may determine their response to chemical challenges imposed by the food plant.
    Aboveground herbivory affects indirect defences of brassicaceous plants against the root feeder Delia radicum Linnaeus: laboratory and field evidence
    Pierre, P.S. ; Dugravot, S. ; Ferry, A. ; Soler, R. ; Dam, N.M. van; Cortesero, A.M. - \ 2011
    Ecological Entomology 36 (2011)3. - ISSN 0307-6946 - p. 326 - 334.
    natural enemies - entomopathogenic nematodes - specialist herbivore - insect herbivores - induced volatiles - infochemical use - cabbage plants - host-plant - performance - attraction
    1. Belowground herbivory has recently been shown to disrupt the host location behaviour of aboveground parasitoids and thereby impact plants indirect defences. Reverse interactions, on the other hand, have received little attention so far. 2. Lab and field studies were conducted to examine whether the presence of the leaf herbivore Pieris brassicae Linnaeus on brassicaceous plants influences the response of Trybliographa rapae Westwood, a specialist parasitoid of the root feeder Delia radicum Linnaeus. 3. The present results show that the attraction of the parasitoid towards host-infested plants disappeared when these plants were also infested by P. brassicae. This absence of attraction was observed both when the complete odour blend or only undamaged leaves from damaged plants were offered, emphasising the role of systemically induced volatiles for host location in T. rapae. 4. Furthermore, the field study revealed that parasitism levels dropped from 30% on root-infested plants to 4% on double-infested plants. 5. The present study is the first to confirm that reduced attraction to host-infested plants as a result of simultaneous attack by below- and aboveground herbivores translates into lower levels of parasitism in the field.
    Identification of Biologically Relevant Compounds in Aboveground and Belowground Induced Volatile Blends
    Dam, N.M. van; Qiu, B.L. ; Hordijk, C.A. ; Vet, L.E.M. ; Jansen, J.J. - \ 2010
    Journal of Chemical Ecology 36 (2010)9. - ISSN 0098-0331 - p. 1006 - 1016.
    herbivore-induced volatiles - partial least-squares - jasmonic acid - specialist herbivore - cotesia-glomerata - parasitic wasps - natural enemies - plants - root - performance
    Plants under attack by aboveground herbivores emit complex blends of volatile organic compounds (VOCs). Specific compounds in these blends are used by parasitic wasps to find their hosts. Belowground induction causes shifts in the composition of aboveground induced VOC blends, which affect the preference of parasitic wasps. To identify which of the many volatiles in the complex VOC blends may explain parasitoid preference poses a challenge to ecologists. Here, we present a case study in which we use a novel bioinformatics approach to identify biologically relevant differences between VOC blends of feral cabbage (Brassica oleracea L.). The plants were induced aboveground or belowground with jasmonic acid (JA) and shoot feeding caterpillars (Pieris brassicae or P. rapae). We used Partial Least Squares--Discriminant Analysis (PLSDA) to integrate and visualize the relation between plant-emitted VOCs and the preference of female Cotesia glomerata. Overall, female wasps preferred JA-induced plants over controls, but they strongly preferred aboveground JA-induced plants over belowground JA-induced plants. PLSDA revealed that the emission of several monoterpenes was enhanced similarly in all JA-treated plants, whereas homoterpenes and sesquiterpenes increased exclusively in aboveground JA-induced plants. Wasps may use the ratio between these two classes of terpenes to discriminate between aboveground and belowground induced plants. Additionally, it shows that aboveground applied JA induces different VOC biosynthetic pathways than JA applied to the root. Our bioinformatic approach, thus, successfully identified which VOCs matched the preferences of the wasps in the various choice tests. Additionally, the analysis generated novel hypotheses about the role of JA as a signaling compound in aboveground and belowground induced responses in plants
    Ecological fits, mis-fits and lotteries involving insect herbivores on the invase plant, Bunias orientalis
    Harvey, J.A. ; Biere, A. ; Fortuna, T.F.M. ; Vet, L.E.M. ; Engelkes, T. ; Morriën, W.E. ; Gols, R. ; Verhoeven, K.J.F. ; Vogel, H. ; Macel, M. ; Heidel-Fischer, H.M. ; Schramm, K. ; Putten, W.H. van der - \ 2010
    Biological Invasions 12 (2010)9. - ISSN 1387-3547 - p. 3045 - 3059.
    enemy release hypothesis - pieris-rapae - specialist herbivore - host-specificity - evolution - deterrents - community - larvae - associations - coevolution
    Exotic plants bring with them traits that evolved elsewhere into their new ranges. These traits may make them unattractive or even toxic to native herbivores, or vice versa. Here, interactions between two species of specialist (Pieris rapae and P. brassicae) and two species of generalist (Spodoptera exigua and Mamestra brassicae) insect herbivores were examined on two native crucifer species in the Netherlands, Brassica nigra and Sinapis arvensis, and an exotic, Bunias orientalis. Bu. orientalis originates in eastern Europe and western Asia but is now an invasive pest in many countries in central Europe. P. rapae, P. brassicae and S. exigua performed very poorly on Bu. orientalis, with close to 100% of larvae failing to pupate, whereas survival was much higher on the native plants. In choice experiments, the pierid butterflies preferred to oviposit on the native plants. Alternatively, M. brassicae developed very poorly on the native plants but thrived on Bu. orientalis. Further assays with a German Bu. orientalis population also showed that several specialist and generalist herbivores performed very poorly on this plant, with the exception of Spodoptera littoralis and M. brassicae. Bu. orientalis produced higher levels of secondary plant compounds (glucosinolates) than B. nigra but not S. arvensis but these do not appear to be important factors for herbivore development. Our results suggest that Bu. orientalis is a potential demographic ‘trap’ for some herbivores, such as pierid butterflies. However, through the effects of an evolutionary ‘lottery’, M. brassicae has found its way through the plant’s chemical ‘minefield’.
    Are population differences in plant quality reflected in the preference and performance of two endoparasitoid wasps?
    Gols, R. ; Dam, N.M. van; Raaijmakers, C.E. ; Dicke, M. ; Harvey, J.A. - \ 2009
    Oikos 118 (2009)5. - ISSN 0030-1299 - p. 733 - 743.
    diadegma-semiclausum hellen - host-searching behavior - natural enemies - specialist herbivore - chemical defense - tritrophic interactions - cotesia-glomerata - genetic-variation - pieris-brassicae - food plants
    In recent years, increasing attention has been paid in exploring the role of direct plant defence, through the production of allelochemicals, on the performance of parasitoid wasps and their hosts. However, few studies have determined if parasitoids can detect differences in plant quality and thus preferentially attack hosts on which their progeny develop most successfully. In this study we examined the development and preference of two endoparasitoids, Diadegmasemiclausum and Cotesia glomerata, developing in larvae of their respective hosts, Plutella xylostella and Pieris brassicae. In turn, these were reared on different wild populations of black mustard Brassica nigra originating in the Netherlands and Sicily (Italy), as well as single cultivated strains of B. nigra and brown mustard, B. juncea. Chemical analyses of foliar glucosinolates and volatile emissions by P. xylostella-damaged plants revealed large differences between B. nigra and B. juncea plants, with smaller differences among the B. nigra populations. The four mustard populations differentially affected development time and body mass of the herbivores and parasitoids. Contrasts among the means revealed significant differences mainly between B. nigra and B. juncea. Both parasitoids, however, preferred to alight on plants in which their progeny developed most successfully. In behavioural bioassays, D. semiclausum did not discriminate among the B. nigra populations and preferred to alight on B. juncea, which was the best plant population for parasitoid development. By contrast, C. glomerata females exhibited the lowest preference for Italian B. nigra populations, on which adult parasitoid size was the smallest. These results reveal that parasitoids can detect even small differences in plant quality presumably through their volatile blends and that plant preference and offspring performance in the two species are 'optimally synchronized'.
    Effects of dietary nicotine on the development of an insect herbivore, its parasitoid and secondary hyperparasitoid over four trophic levels
    Harvey, J.A. ; Dam, N.M. van; Witjes, L.M.A. ; Soler, R. ; Gols, R. - \ 2007
    Ecological Entomology 32 (2007)q. - ISSN 0307-6946 - p. 15 - 23.
    host-plant chemistry - manduca-sexta - cotesia-congregata - specialist herbivore - hyposoter-annulipes - tobacco hornworm - natural enemies - allelochemicals - hymenoptera - performance
    1. Allelochemicals in herbivore diet are known to affect the development of higher trophic levels, such as parasitoids and predators. 2. This study examines how differing levels of nicotine affects the development of a herbivore, its parasitoid and secondary hyperparasitoid over four trophic levels. Separate cohorts of the herbivore, Manduca sexta, were fed on artificial diets containing 0.0, 0.1, and 0.5% wet weights of nicotine. Some of the larvae in each cohort were separately parasitised in the first (L1) and third (L3) instars by the gregarious endoparasitoid, Cotesia congregata. Newly emerged parasitoid cocoons were, in turn, parasitised by the hyperparasitoid, Lysibia nana. 3. Pupal mass in M. sexta was negatively correlated with nicotine concentrations in the artificial diet, although larval development time was unaffected. 4. Hyperparasitoid survival was highest when there were low levels of nicotine in the diet of M. sexta. Cocoon mass in C. congregata and adult mass in L. nana were mostly affected by nicotine levels in host diet when L1 M. sexta larvae were parasitised. The effects were slightly stronger on L. nana than on C. congregata, indicating the presence of both qualitative and quantitative effects of nicotine concentration on both species. 5. The results suggest that allelochemicals in herbivore diet can have both direct and indirect effects on the performance of higher trophic levels. However, in multitrophic interactions these effects can vary with the stage of the herbivore attacked by the primary parasitoid, as well as with the strategy employed by the herbivore to deal with plant phytotoxins.
    Development of an insect herbivore and its pupal parasitoid reflect differences in direct plant defense
    Harvey, J.A. ; Gols, R. ; Wagenaar, R. ; Bezemer, T.M. - \ 2007
    Journal of Chemical Ecology 33 (2007)8. - ISSN 0098-0331 - p. 1556 - 1569.
    4 trophic levels - host-plant - specialist herbivore - phytophagous insects - plutella-xylostella - brassica-oleracea - wild populations - trichoplusia-ni - manduca-sexta - pieris-rapae
    In nature, plants defend themselves by production of allelochemicals that are toxic to herbivores. There may be considerable genetic variation in the expression of chemical defenses because of various selection pressures. In this study, we examined the development of the small cabbage butterfly, Pieris rapae, and its gregarious pupal ectoparasitoid, Pteromalus puparum, when reared on three wild populations (Kimmeridge, Old Harry, Winspit) of cabbage, Brassica oleracea, and a Brussels sprout cultivar. Wild plant populations were obtained from seeds of plants that grow naturally along the south coast of Dorset, England. Significant differences in concentrations of allelochemicals (glucosinolates) were found in leaves of plants damaged by P. rapae. Total glucosinolate concentrations in Winspit plants, the population with the highest total glucosinolate concentration, were approximately four times higher than in the cultivar, the strain with the lowest total glucosinolate concentration. Pupal mass of P. rapae and adult body mass of Pt. puparum were highest when reared on the cultivar and lowest when developing on Kimmeridge plants, the wild strain with the lowest total glucosinolate concentration. Development of male parasitoids was also more negatively affected than female parasitoids. Our results reveal that plant quality, at least for the development of 'adapted' oligophagous herbivores, such as P. rapae, is not based on total glucosinolate content. The only glucosinolate compound that corresponded with the performance of P. rapae was the indole glucosinolate, neoglucobrassicin. Our results show that performance of ectoparasitoids may closely reflect constraints on the development of the host.
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