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Drought and root herbivory interact to alter the response of above-ground parasitoids to aphid infested plants and associated plant volatile signals.

Tariq M, Wright DJ, Bruce TJ, Staley JT - PLoS ONE (2013)

Bottom Line: We examined the effect of drought, with and without root herbivory, on the olfactory response of parasitoids (preference), plant volatile emissions, parasitism success (performance), and the effect of drought on root herbivory.There was a significant interaction between drought and root herbivory on the efficacy of the two parasitoid species, drought stress partially reversing the negative effect of root herbivory on percent parasitism.Plant emissions of VOCs were reduced by drought and root herbivores, and in olfactometer experiments parasitoids preferred the odour from well-watered plants compared with other treatments.

View Article: PubMed Central - PubMed

Affiliation: Division of Biology, Faculty of Natural Sciences, Imperial College London, Silwood Park Campus, Ascot, United Kingdom. m.tariq06@imperial.ac.uk

ABSTRACT
Multitrophic interactions are likely to be altered by climate change but there is little empirical evidence relating the responses of herbivores and parasitoids to abiotic factors. Here we investigated the effects of drought on an above/below-ground system comprising a generalist and a specialist aphid species (foliar herbivores), their parasitoids, and a dipteran species (root herbivore).We tested the hypotheses that: (1) high levels of drought stress and below-ground herbivory interact to reduce the performance of parasitoids developing in aphids; (2) drought stress and root herbivory change the profile of volatile organic chemicals (VOCs) emitted by the host plant; (3) parasitoids avoid ovipositing in aphids feeding on plants under drought stress and root herbivory. We examined the effect of drought, with and without root herbivory, on the olfactory response of parasitoids (preference), plant volatile emissions, parasitism success (performance), and the effect of drought on root herbivory. Under drought, percentage parasitism of aphids was reduced by about 40-55% compared with well watered plants. There was a significant interaction between drought and root herbivory on the efficacy of the two parasitoid species, drought stress partially reversing the negative effect of root herbivory on percent parasitism. In the absence of drought, root herbivory significantly reduced the performance (e.g. fecundity) of both parasitoid species developing in foliar herbivores. Plant emissions of VOCs were reduced by drought and root herbivores, and in olfactometer experiments parasitoids preferred the odour from well-watered plants compared with other treatments. The present work demonstrates that drought stress can change the outcome of interactions between herbivores feeding above- and below-ground and their parasitoids, mediated by changes in the chemical signals from plants to parasitoids. This provides a new insight into how the structure of terrestrial communities may be affected by drought.

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Performance of Aphidius colemani and Diaeretiella rapae (mean ± S.E.M.) of Myzus persicae and Brevicoryne brassicae reared on Brassica oleracea plants under a well-watered regime (200 ml/pot/week; “Control”) and a reduced water regime (100 ml/pot/week; “Drought stressed”) with/without Delia radicum.Within each parasitoid species, means with different letters are significantly different (P<0.05): (a) Percentage parasitism (b) sex ratio (c) percentage emergence (d) female tibia length (mm) and (e) adult longevity (days). A high sex ratio indicates a high proportion of male parasitoids.
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pone-0069013-g001: Performance of Aphidius colemani and Diaeretiella rapae (mean ± S.E.M.) of Myzus persicae and Brevicoryne brassicae reared on Brassica oleracea plants under a well-watered regime (200 ml/pot/week; “Control”) and a reduced water regime (100 ml/pot/week; “Drought stressed”) with/without Delia radicum.Within each parasitoid species, means with different letters are significantly different (P<0.05): (a) Percentage parasitism (b) sex ratio (c) percentage emergence (d) female tibia length (mm) and (e) adult longevity (days). A high sex ratio indicates a high proportion of male parasitoids.

Mentions: Percentage parasitism. Percentage parasitism was significantly affected by the interaction between drought stress, De. radicum and parasitoid species (F1, 72 = 7.50; P<0.01). Drought stress (F1, 72 = 121.39; P<0.001) and the presence of De. radicum (F1, 72 = 10.27; P<0.01) had a negative impact on percentage parasitism by both parasitoid species compared with well watered plants, but their effects were greater for the specialist parasitoid species (D. rapae) than for the generalist parasitoid species (A. colemani, Figure 1a). Drought stress partially reversed the negative effect of De. radicum on parasitism by A. colemani (Figure 1a; Tukey’s HSD, P<0.05). Parasitism by D. rapae followed the same pattern, but the difference between drought stressed plants with or without De. radicum was not significant (Figure 1a).


Drought and root herbivory interact to alter the response of above-ground parasitoids to aphid infested plants and associated plant volatile signals.

Tariq M, Wright DJ, Bruce TJ, Staley JT - PLoS ONE (2013)

Performance of Aphidius colemani and Diaeretiella rapae (mean ± S.E.M.) of Myzus persicae and Brevicoryne brassicae reared on Brassica oleracea plants under a well-watered regime (200 ml/pot/week; “Control”) and a reduced water regime (100 ml/pot/week; “Drought stressed”) with/without Delia radicum.Within each parasitoid species, means with different letters are significantly different (P<0.05): (a) Percentage parasitism (b) sex ratio (c) percentage emergence (d) female tibia length (mm) and (e) adult longevity (days). A high sex ratio indicates a high proportion of male parasitoids.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3716814&req=5

pone-0069013-g001: Performance of Aphidius colemani and Diaeretiella rapae (mean ± S.E.M.) of Myzus persicae and Brevicoryne brassicae reared on Brassica oleracea plants under a well-watered regime (200 ml/pot/week; “Control”) and a reduced water regime (100 ml/pot/week; “Drought stressed”) with/without Delia radicum.Within each parasitoid species, means with different letters are significantly different (P<0.05): (a) Percentage parasitism (b) sex ratio (c) percentage emergence (d) female tibia length (mm) and (e) adult longevity (days). A high sex ratio indicates a high proportion of male parasitoids.
Mentions: Percentage parasitism. Percentage parasitism was significantly affected by the interaction between drought stress, De. radicum and parasitoid species (F1, 72 = 7.50; P<0.01). Drought stress (F1, 72 = 121.39; P<0.001) and the presence of De. radicum (F1, 72 = 10.27; P<0.01) had a negative impact on percentage parasitism by both parasitoid species compared with well watered plants, but their effects were greater for the specialist parasitoid species (D. rapae) than for the generalist parasitoid species (A. colemani, Figure 1a). Drought stress partially reversed the negative effect of De. radicum on parasitism by A. colemani (Figure 1a; Tukey’s HSD, P<0.05). Parasitism by D. rapae followed the same pattern, but the difference between drought stressed plants with or without De. radicum was not significant (Figure 1a).

Bottom Line: We examined the effect of drought, with and without root herbivory, on the olfactory response of parasitoids (preference), plant volatile emissions, parasitism success (performance), and the effect of drought on root herbivory.There was a significant interaction between drought and root herbivory on the efficacy of the two parasitoid species, drought stress partially reversing the negative effect of root herbivory on percent parasitism.Plant emissions of VOCs were reduced by drought and root herbivores, and in olfactometer experiments parasitoids preferred the odour from well-watered plants compared with other treatments.

View Article: PubMed Central - PubMed

Affiliation: Division of Biology, Faculty of Natural Sciences, Imperial College London, Silwood Park Campus, Ascot, United Kingdom. m.tariq06@imperial.ac.uk

ABSTRACT
Multitrophic interactions are likely to be altered by climate change but there is little empirical evidence relating the responses of herbivores and parasitoids to abiotic factors. Here we investigated the effects of drought on an above/below-ground system comprising a generalist and a specialist aphid species (foliar herbivores), their parasitoids, and a dipteran species (root herbivore).We tested the hypotheses that: (1) high levels of drought stress and below-ground herbivory interact to reduce the performance of parasitoids developing in aphids; (2) drought stress and root herbivory change the profile of volatile organic chemicals (VOCs) emitted by the host plant; (3) parasitoids avoid ovipositing in aphids feeding on plants under drought stress and root herbivory. We examined the effect of drought, with and without root herbivory, on the olfactory response of parasitoids (preference), plant volatile emissions, parasitism success (performance), and the effect of drought on root herbivory. Under drought, percentage parasitism of aphids was reduced by about 40-55% compared with well watered plants. There was a significant interaction between drought and root herbivory on the efficacy of the two parasitoid species, drought stress partially reversing the negative effect of root herbivory on percent parasitism. In the absence of drought, root herbivory significantly reduced the performance (e.g. fecundity) of both parasitoid species developing in foliar herbivores. Plant emissions of VOCs were reduced by drought and root herbivores, and in olfactometer experiments parasitoids preferred the odour from well-watered plants compared with other treatments. The present work demonstrates that drought stress can change the outcome of interactions between herbivores feeding above- and below-ground and their parasitoids, mediated by changes in the chemical signals from plants to parasitoids. This provides a new insight into how the structure of terrestrial communities may be affected by drought.

Show MeSH
Related in: MedlinePlus