Drought stress affects plant metabolites and herbivore preference but not host location by its parasitoids
Weldegergis, B.T. ; Zhu, F. ; Poelman, E.H. ; Dicke, M. - \ 2015
Oecologia 177 (2015)3. - ISSN 0029-8549 - p. 701 - 713.
volatile emissions - water-stress - abiotic factors - oviposition - genes - biosynthesis - consequences - lepidoptera - complexity - expression
One of the main abiotic stresses that strongly affects plant survival and the primary cause of crop loss around the world is drought. Drought stress leads to sequential morphological, physiological, biochemical and molecular changes that can have severe effects on plant growth, development and productivity. As a consequence of these changes, the interaction between plants and insects can be altered. Using cultivated Brassica oleracea plants, the parasitoid Microplitis mediator and its herbivorous host Mamestra brassicae, we studied the effect of drought stress on (1) the emission of plant volatile organic compounds (VOCs), (2) plant hormone titres, (3) preference and performance of the herbivore, and (4) preference of the parasitoid. Higher levels of jasmonic acid (JA) and abscisic acid (ABA) were recorded in response to herbivory, but no significant differences were observed for salicylic acid (SA) and indole-3-acetic acid (IAA). Drought significantly impacted SA level and showed a significant interactive effect with herbivory for IAA levels. A total of 55 VOCs were recorded and the difference among the treatments was influenced largely by herbivory, where the emission rate of fatty acid-derived volatiles, nitriles and (E)-4,8-dimethylnona-1,3,7-triene [(E)-DMNT] was enhanced. Mamestra brassicae moths preferred to lay eggs on drought-stressed over control plants; their offspring performed similarly on plants of both treatments. VOCs due to drought did not affect the choice of M. mediator parasitoids. Overall, our study reveals an influence of drought on plant chemistry and insect-plant interactions.
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.
Reproductive escape: annual plant responds to butterfly eggs by accelerating seed production
Lucas-Barbosa, D. ; Loon, J.J.A. van; Gols, R. ; Beek, T.A. van; Dicke, M. - \ 2013
Functional Ecology 27 (2013)1. - ISSN 0269-8463 - p. 245 - 254.
pieris-brassicae - raphanus-raphanistrum - solanum-carolinense - volatile emissions - flower visitation - insect eggs - herbivory - pollinators - ecology - defense
1.Plants respond to insect herbivores with changes in physical and chemical traits, both locally and systemically, in leaves and flowers. Such phenotypic changes may influence the behaviour of every community member that interacts with the plant. Here, we address effects of plant responses to eggs and subsequent herbivory by caterpillars on plant-mediated interactions with pollinators and consequences for plant fitness. 2.Using a common garden set-up, we have investigated responses of Brassica nigra plants to herbivore exposure from egg deposition onwards throughout larval development. We quantified effects of infestation by the specialist Pieris brassicae on: 1. behaviour of pollinators; 2. volatile emission and 3. timing and number of seeds produced. 3.Egg deposition and folivory did not influence visitation by pollinators to plots of infested or control plants. Effects of herbivore infestation on both pollinator visitation and volatile emission were observed only at a later stage, when caterpillars were feeding on the flowers. 4.Remarkably, before eggs had hatched, infested plants accelerated seed production. The caterpillars that developed from the eggs fed on flowers but not on seeds and thus seed production prior to herbivory on flowers safeguarded reproductive output. 5.The results of this study show that early plant investments in reproduction can successfully prevent consumption of expensive reproductive tissues. By accelerating seed production, plants prevented consumption of flowers and effectively defended themselves against the herbivores
Whiteflies interfere with indirect plant defense against spider mites in Lima bean
Zhang, P.J. ; Zheng, S.J. ; Loon, J.J.A. van; Boland, W. ; David, A. ; Mumm, R. ; Dicke, M. - \ 2009
Proceedings of the National Academy of Sciences of the United States of America 106 (2009)50. - ISSN 0027-8424 - p. 21202 - 21207.
octadecanoid-signaling pathway - jasmonic acid - salicylic-acid - volatile emissions - host-plant - spodoptera-littoralis - arabidopsis-thaliana - brassica-oleracea - herbivore - responses
Plants under herbivore attack are able to initiate indirect defense by synthesizing and releasing complex blends of volatiles that attract natural enemies of the herbivore. However, little is known about how plants respond to infestation by multiple herbivores, particularly if these belong to different feeding guilds. Here, we report the interference by a phloem-feeding insect, the whitefly Bemisia tabaci, with indirect plant defenses induced by spider mites (Tetranychus urticae) in Lima bean (Phaseolus lunatus) plants. Additional whitefly infestation of spider-mite infested plants resulted in a reduced attraction of predatory mites (Phytoseiulus persimilis) compared to attraction to plants infested by spider mites only. This interference is shown to result from the reduction in (E)-ß-ocimene emission from plants infested by both spider mites and whiteflies. When using exogenous salicylic acid (SA) application to mimic B. tabaci infestation, we observed similar results in behavioral and chemical analyses. Phytohormone and gene-expression analyses revealed that B. tabaci infestation, as well as SA application, inhibited spider mite-induced jasmonic acid (JA) production and reduced the expression of two JA-regulated genes, one of which encodes for the P. lunatus enzyme ß-ocimene synthase that catalyzes the synthesis of (E)-ß-ocimene. Remarkably, B. tabaci infestation concurrently inhibited SA production induced by spider mites. We therefore conclude that in dual-infested Lima bean plants the suppression of the JA signaling pathway by whitefly feeding is not due to enhanced SA levels.
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.
Flexible use of patch-leaving mechanisms in a parasitoid wasp
Burger, J.M.S. ; Huang, Y. ; Hemerik, L. ; Lenteren, J.C. van; Vet, L.E.M. - \ 2006
Journal of Insect Behavior 19 (2006)2. - ISSN 0892-7553 - p. 155 - 170.
encarsia-formosa hymenoptera - vaporariorum homoptera-aleyrodidae - time allocation - trialeurodes-vaporariorum - host relationship - infochemical use - commercial glasshouse - population-dynamics - volatile emissions - venturia-canescens
Classical optimal-foraging theory predicts that a parasitoid is less likely to leave a patch after a host encounter when the host distribution is aggregated, whereas a parasitoid is more likely to leave after a host encounter when the host distribution is regular. Field data on host distributions in the area of origin of the whitefly parasitoid Encarsia formosa showed that whiteflies aggregate at several spatial scales. However, infested leaves most likely contained a single host. This suggests that a host encounter is not enough to decide when to leave. We therefore tested the effect of host distribution and parasitoid experience on patch-leaving behavior. Each parasitoid was observed for several consecutive days in a three-dimensional arena with leaflets containing on average one host per leaflet in an either regular or aggregated host distribution. A proportional hazards model showed that a host encounter decreased the leaving tendency on a leaflet with one host when the time since the latest host encounter was short, but increased the leaving tendency when the time since the latest host encounter was long, independent of host distribution. We conclude that a parasitoid can switch from decreasing to increasing its tendency to leave a patch after a host encounter. We propose two hypotheses that may explain the evolution of such a switching mechanism.
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