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| 2. |
- Saveer, Ahmed, et al.
(författare)
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A herbivore-induced plant volatile interferes with host plant and mate location in moths through suppression of olfactory signalling pathways
- 2015
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Ingår i: BMC Biology. - : Springer Science and Business Media LLC. - 1741-7007. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Background: Plants under herbivore attack release volatiles that attract natural enemies, and herbivores in turn avoid such plants. Whilst herbivore-induced plant volatile blends appeared to reduce the attractiveness of host plants to herbivores, the volatiles that are key in this process and particularly the way in which deterrence is coded in the olfactory system are largely unknown. Here we demonstrate that herbivore-induced cotton volatiles suppress orientation of the moth Spodoptera littoralis to host plants and mates.Results: We found that (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), an induced volatile, is key in herbivore deterrence: DMNT suppressed plant odour-and pheromone-induced behaviours. We then dissected the neurophysiological basis of this interaction. DMNT-responding glomeruli were also activated by other plant compounds, suggesting that S. littoralis possesses no segregated olfactory circuit dedicated exclusively to DMNT. Instead, DMNT suppressed responses to the main pheromone component, (Z)-9-(E)-11-tetradecenyl acetate, and primarily to (Z)-3-hexenyl acetate, a host plant attractant.Conclusion: Our study shows that olfactory sensory inhibition, which has previously been reported without reference to an animal's ecology, can be at the core of coding of ecologically relevant odours. As DMNT attracts natural enemies and deters herbivores, it may be useful in the development or enhancement of push-pull strategies for sustainable agriculture.
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| 3. |
- Hambäck, Peter, et al.
(författare)
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Mating affects resource selection and modulates associational effects between neighbouring resources
- 2017
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 126, s. 1708-1716
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Tidskriftsartikel (refereegranskat)abstract
- Associational effects occur when the attack rate on a resource depends on neighbouring resources in the environment. These effects are predicted to result from mismatches experienced by the consumer organism in resource selection along hierarchical search levels. As resource selection depends on sensory information used during search behaviour, we expected that different physiological states of an insect might modulate the outcome of associational effects due to differences in resource selection. We used Drosophila melanogaster, as a model organism for olfactory-guided behaviour in insects, to study the effects of mating induced behavioural changes on associational effects between two alternative resources. We found that mating has no effect on the ability of D. melanogaster to locate resource patches, but rather affects the perception of the resources within the patch. Consequently, we only found associational effects in the experiments with unmated females and not in the experiments with mated females. Our results suggest that the lack of associational effects for mated females resulted from changes in the use of short-range olfactory cues, leading to random selection among the resources. In conclusion, our results suggest that the physiological state of an insect modulates associational effects by affecting resource selection rates within the patch.
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| 4. |
- Verschut, Thomas A., et al.
(författare)
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Disentangling associational effects : both resource density and resource frequency affect search behaviour in complex environments
- 2016
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 30:11, s. 1826-1833
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Tidskriftsartikel (refereegranskat)abstract
- Neighbouring resources have been found to either decrease or increase the likelihood that a consumer organism attacks a focal resource. These phenomena are referred to as associational resistance (AR) and associational susceptibility (AS), respectively. While associational effects have been observed in various field studies, little is known on how resource heterogeneity can cause associational effects. We used a laboratory approach in which we studied the effects of resource density and frequency in the search behaviour of Drosophila melanogaster as a model organism for olfactory-guided behaviour in insects. We first determined whether D.melanogaster could discriminate between odour sources that differ quantitatively. Secondly, we determined what the effect of resource density and frequency was on the search behaviour of D.melanogaster by combining these resources into various patch arrangements. Finally, we used the outcome of our experiments to disentangle the role of resource density and frequency in associational effects. We found that D.melanogaster has the ability to discriminate between quantitatively different resources, but that the attraction to resource density is constrained by an optimum after which attraction decreases. Furthermore, in heterogeneous environments, flies showed a strong preference towards the more apparent resource, leading to AS for the more apparent resources and AR for the less apparent resource. The strength of this interaction increased with a decreasing frequency of the more apparent resource. These results imply that D.melanogaster mainly selects patches at the level of individual resources. Consequently, when a patch contains qualitatively different resources, the more apparent resource will attract a higher number of flies than the less apparent resource irrespective of the frequency of the apparent resource within the patch. Our study shows that associational effects can be explained by determining the hierarchical level at which a consumer selects its resources. When a consumer selects resources at the individual level rather than at the patch level, our results can be used to explain the population dynamics of host plants and their associated consumers under field conditions.
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| 5. |
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| 6. |
- Verschut, Thomas Alexander, 1988-
(författare)
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Searching for food in complex environments : Integrating processes at multiple spatial scales
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Resources are often unevenly distributed through the environment, resulting in a challenging task for insects to locate food, mates and oviposition sites. Consequently, there is an ongoing need to unravel how insects rely on behavioural and sensory traits while searching for resources in heterogeneous environments. In the first part of this thesis, I addressed this issue by studying how neighbouring resources can affect the likelihood of insects finding their preferred host resources. These effects of neighbouring resources are commonly referred to as associational effects, and are expected to result from limitations in the sensory physiology of insects. Such limitations constrain the insect’s ability to correctly evaluate resource quality at the different steps involved in insect search behaviour. Furthermore, I determined whether the physiological state of an insect, and sensory experiences made during larval stages, can affect host search behaviour in heterogeneous environments.By comparing the behaviour of Drosophila melanogaster in environments with single and multiple resources, I found that the presence of neighbouring recourses increased the selection rates for attractive resources, while it decreased the selection rates for less attractive resources. These effects are referred to as associational susceptibility and associational resistance respectively. Furthermore, by studying oviposition behaviour, I found that during these small-scale behavioural decisions, associational effects are mainly governed by gustatory mediated selection and less by olfactory mediated selection. The oviposition assay eliminated potential misinterpretations of resource quality along the different steps of search behaviour, hence the results suggested that associational effects rely on distinctive selection behaviour between resource types rather than on sensory constraints.In the second part of this thesis I determined whether natal experiences can be used by insects as sensory shortcuts to find host resources, and whether this leads to better larval performance on those selected host resources. For this purpose, I studied the interactions between the larval parasitoid Asecodes lucens and the oligophagous leaf beetle Galerucella sagittariae. The results showed that the relationship between oviposition preference and larval performance, of both insect species, depends on an interactive effect between the insects’ natal origin and the quality of the different host resources. Moreover, I found that the natal origin was a better predictor for the adult host preference, rather than for larval performance. This suggests that, aside from the actual quality of the host resources, locating any suitable host might be even more limiting for the female’s fitness.
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| 7. |
- Verschut, Thomas A., et al.
(författare)
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Sensory mutations in Drosophila melanogaster influence associational effects between resources during oviposition
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Neighboring resources can affect insect oviposition behavior when the complexity of sensory information obscures information about host resource availability in heterogeneous resource patches. These effects are referred to as associational effects and are hypothesized to occur through constraints in the sensory processing of the insect during host search, resulting into suboptimal resource use. Because the possibilities to study these constraints on naturally occurring animals are limited, we instead used sensory mutants of Drosophila melanogaster to determine the importance of sensory information in the occurrence of associational effects. We found that oviposition was mainly governed by non-volatile chemical cues and less by volatile cues. Moreover, the loss of gustatory sensilla resulted in random resource selection and eliminated associational effects. In conclusion, our study shows that associational effects do not necessarily depend on constraints in the sensory evaluation of resource quality, but may instead be a direct consequence of distinctive selection behavior between different resources at small scales.
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| 8. |
- Zakir, Ali, et al.
(författare)
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Herbivore-Induced Changes in Cotton Modulates Reproductive Behavior in the Moth Spodoptera littoralis
- 2017
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Ingår i: Frontiers in Ecology and Evolution. - : Frontiers Media SA. - 2296-701X. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Plants produce chemical defense compounds to resist herbivore attack either by repelling the herbivores or attracting natural enemies of the herbivores. We have previously shown that volatile compounds from cotton released in response to herbivory by conspecifics reduce oviposition in cotton leafworm moth Spodoptera littoralis. It remained, however, unclear whether herbivore-induced changes also affect moth pre-mating and mating behaviors. In this study we examined the effect of herbivore-induced changes in cotton on reproductive behaviors i.e., female calling,male attraction and investment, and mating behavior in S. littoralis. We found a reduction in the number of females calling i.e., females releasing pheromone, in the presence of cotton plants damaged by larvae of S. littoralis compared to undamaged plants. Females also spent significantly less time calling and showed a delay in calling in the presence of damaged plants. Furthermore, males exhibited significantly delayed activation and reduced attraction toward female sex pheromone in the presence of damaged plants. We also found that mating success and the number of matings were significantly reduced in the presence of damaged plants whereas male investment i.e., spermatophore weight, was not affected. Thus, our study provides evidence that herbivory by conspecifics on host plants affect pre-mating and mating behaviors in an insect herbivore.
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| 9. |
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| 10. |
- Zakir, Ali, et al.
(författare)
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Specific response to herbivore-induced de novo synthesized plant volatiles provides reliable information for host plant selection in a moth
- 2013
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 216, s. 3257-3263
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Tidskriftsartikel (refereegranskat)abstract
- Animals depend on reliable sensory information for accurate behavioural decisions. For herbivorous insects it is crucial to find host plants for feeding and reproduction, and these insects must be able to differentiate suitable from unsuitable plants. Volatiles are important cues for insect herbivores to assess host plant quality. It has previously been shown that female moths of the Egyptian cotton leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae), avoid oviposition on damaged cotton Gossypium hirsutum, which may mediated by herbivore-induced plant volatiles (HIPVs). Among the HIPVs, some volatiles are released following any type of damage while others are synthesized de novo and released by the plants only in response to herbivore damage. In behavioural experiments we here show that oviposition by S. littoralis on undamaged cotton plants was reduced by adding volatiles collected from plants with ongoing herbivory. Gas chromatography–electroantennographic detection (GC–EAD) recordings revealed that antennae of mated S. littoralis females responded to 18 compounds from a collection of headspace volatiles of damaged cotton plants. Among these compounds, a blend of the seven de novo synthesized volatile compounds was found to reduce oviposition in S. littoralis on undamaged plants under both laboratory and ambient (field) conditions in Egypt. Volatile compounds that are not produced de novo by the plants did not affect oviposition. Our results show that ovipositing females respond specifically to the de novo synthesized volatiles released from plants under herbivore attack. We suggest that these volatiles provide reliable cues for ovipositing females to detect plants that could provide reduced quality food for their offspring and an increased risk of competition and predation.
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