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Natural enemies act faster than endophytic fungi in population control of cereal aphids


Härri, S A; Krauss, J; Müller, C B (2008). Natural enemies act faster than endophytic fungi in population control of cereal aphids. Journal of Animal Ecology, 77(3):605-611.

Abstract

1.
Fast-growing populations of phytophagous insects can be limited by the presence of natural enemies and by alkaloids that are produced by symbiotic associations of many temperate grass species with endophytic fungi. It is unclear if and how acquired plant defences derived from endophytic fungi interact with natural enemies to affect phytophagous insect populations.
2.
To assess the relative importance of endophytic fungi compared to that of natural enemies on the population dynamics of phytophagous insects, we carried out a fully factorial field experiment, in which the presence of natural enemies and the presence of endophytic fungi were manipulated simultaneously. Target colonies of aphids were monitored for 8 weeks starting from their natural appearance in the field to the end of the aphid season.
3.
We show that on Lolium perenne increased natural enemy densities reduced the individual numbers of two common cereal aphids, Rhopalosiphum padi and Metopolophium festucae.
4.
The presence of the endophytic fungi Neotyphodium lolii
reduced the number of M. festucae but did not affect the number of R. padi. The reduction in R. padi numbers by predators and parasitoids was not influenced by the presence of endophytes. For adult M. festucae, however, the negative
effects of natural enemies were significant only in the absence of endophytes.
5.
Over the duration of the experiment, the effect of natural enemies on aphid colony growth was much stronger than the effect of the endophytic fungi N. lolii, presumably because predator and parasitoid action on aphid colonies is much faster than any effects of endophytes.
6.
Our results demonstrate that with simultaneous action of acquired endosymbionts and natural enemies, both factors can control aphid colony growth but they generally act independently of each other.

Abstract

1.
Fast-growing populations of phytophagous insects can be limited by the presence of natural enemies and by alkaloids that are produced by symbiotic associations of many temperate grass species with endophytic fungi. It is unclear if and how acquired plant defences derived from endophytic fungi interact with natural enemies to affect phytophagous insect populations.
2.
To assess the relative importance of endophytic fungi compared to that of natural enemies on the population dynamics of phytophagous insects, we carried out a fully factorial field experiment, in which the presence of natural enemies and the presence of endophytic fungi were manipulated simultaneously. Target colonies of aphids were monitored for 8 weeks starting from their natural appearance in the field to the end of the aphid season.
3.
We show that on Lolium perenne increased natural enemy densities reduced the individual numbers of two common cereal aphids, Rhopalosiphum padi and Metopolophium festucae.
4.
The presence of the endophytic fungi Neotyphodium lolii
reduced the number of M. festucae but did not affect the number of R. padi. The reduction in R. padi numbers by predators and parasitoids was not influenced by the presence of endophytes. For adult M. festucae, however, the negative
effects of natural enemies were significant only in the absence of endophytes.
5.
Over the duration of the experiment, the effect of natural enemies on aphid colony growth was much stronger than the effect of the endophytic fungi N. lolii, presumably because predator and parasitoid action on aphid colonies is much faster than any effects of endophytes.
6.
Our results demonstrate that with simultaneous action of acquired endosymbionts and natural enemies, both factors can control aphid colony growth but they generally act independently of each other.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Uncontrolled Keywords:bottom-up control, microbes, multitrophic interactions, predator exclusion, top-down control
Language:English
Date:2008
Deposited On:16 Jan 2009 13:25
Last Modified:05 Apr 2016 12:37
Publisher:Wiley-Blackwell
ISSN:0021-8790
Additional Information:The definitive version is available at www.blackwell-synergy.com
Publisher DOI:https://doi.org/10.1111/j.1365-2656.2008.01373.x
PubMed ID:18312338

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