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Diet of generalist predators reflects effects of cropping period and farming system on extra- and intraguild prey

Roubinet, Eve; Birkhofer, Klaus LU ; Malsher, Gerard; Staudacher, Karin; Ekbom, Barbara; Traugott, Michael and Jonsson, Mattias (2017) In Ecological Applications 27(4). p.1167-1177
Abstract

The suppression of agricultural pests by natural enemies, including generalist arthropod predators, is an economically important regulating ecosystem service. Besides pests, generalist predators may also consume non-pest extraguild and intraguild prey, which can affect their impact on pest populations. This may either reduce the impact of generalist predators on pest populations, because they are diverted from pest predation, or increase it, as it helps them survive periods of low pest availability. However, the availability of pest prey and alternative, non-pest prey can vary over the crop growing season and between farming systems, potentially affecting predator-prey interactions and the levels of biological control. We have limited... (More)

The suppression of agricultural pests by natural enemies, including generalist arthropod predators, is an economically important regulating ecosystem service. Besides pests, generalist predators may also consume non-pest extraguild and intraguild prey, which can affect their impact on pest populations. This may either reduce the impact of generalist predators on pest populations, because they are diverted from pest predation, or increase it, as it helps them survive periods of low pest availability. However, the availability of pest prey and alternative, non-pest prey can vary over the crop growing season and between farming systems, potentially affecting predator-prey interactions and the levels of biological control. We have limited information about how farming systems and environmental variation over the crop growing season influence predator diets. This limits our ability to predict the importance of generalist predators as natural enemies of agricultural pests. Here we utilize molecular gut content analyses to assess detection frequencies of extra- and intraguild prey DNA in generalist predator communities in replicated organically and conventionally managed cereal fields at two key periods of the cropping season for aphid biological control. This is done in order to understand how farming system, crop season, prey availability and predator community composition determine the composition of predator diets. Aphid pests and decomposers (springtails) were equally important prey for generalist predators early in the growing season. Later in the season, the importance of aphid prey increased with increasing aphid densities while springtail predation rates were positively correlated to abundance of this prey at both early and late crop growth stages. Intraguild predation was unidirectional: carabids fed on spiders, whereas spiders rarely fed on carabids. Carabids had higher detection frequencies for the two most common spider families in organically compared to conventionally managed fields. Our study documents that predation by generalist predator communities on aphid pests increases with pest numbers independently of their generally widespread consumption of alternative, non-pest prey. Therefore, conservation strategies in agricultural fields could promote biological control services by promoting high levels of alternative non-pest prey for generalist predator communities.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
aphids, Araneae, biological control, Carabidae, intraguild predation, molecular gut content analyses, organic farming
in
Ecological Applications
volume
27
issue
4
pages
11 pages
publisher
Ecological Society of America
external identifiers
  • scopus:85020192804
  • wos:000402566600011
ISSN
1051-0761
DOI
10.1002/eap.1510
language
English
LU publication?
yes
id
84a8c581-908e-46fc-97ae-7e81ff601992
date added to LUP
2017-06-27 14:04:41
date last changed
2017-09-18 11:43:12
@article{84a8c581-908e-46fc-97ae-7e81ff601992,
  abstract     = {<p>The suppression of agricultural pests by natural enemies, including generalist arthropod predators, is an economically important regulating ecosystem service. Besides pests, generalist predators may also consume non-pest extraguild and intraguild prey, which can affect their impact on pest populations. This may either reduce the impact of generalist predators on pest populations, because they are diverted from pest predation, or increase it, as it helps them survive periods of low pest availability. However, the availability of pest prey and alternative, non-pest prey can vary over the crop growing season and between farming systems, potentially affecting predator-prey interactions and the levels of biological control. We have limited information about how farming systems and environmental variation over the crop growing season influence predator diets. This limits our ability to predict the importance of generalist predators as natural enemies of agricultural pests. Here we utilize molecular gut content analyses to assess detection frequencies of extra- and intraguild prey DNA in generalist predator communities in replicated organically and conventionally managed cereal fields at two key periods of the cropping season for aphid biological control. This is done in order to understand how farming system, crop season, prey availability and predator community composition determine the composition of predator diets. Aphid pests and decomposers (springtails) were equally important prey for generalist predators early in the growing season. Later in the season, the importance of aphid prey increased with increasing aphid densities while springtail predation rates were positively correlated to abundance of this prey at both early and late crop growth stages. Intraguild predation was unidirectional: carabids fed on spiders, whereas spiders rarely fed on carabids. Carabids had higher detection frequencies for the two most common spider families in organically compared to conventionally managed fields. Our study documents that predation by generalist predator communities on aphid pests increases with pest numbers independently of their generally widespread consumption of alternative, non-pest prey. Therefore, conservation strategies in agricultural fields could promote biological control services by promoting high levels of alternative non-pest prey for generalist predator communities.</p>},
  author       = {Roubinet, Eve and Birkhofer, Klaus and Malsher, Gerard and Staudacher, Karin and Ekbom, Barbara and Traugott, Michael and Jonsson, Mattias},
  issn         = {1051-0761},
  keyword      = {aphids,Araneae,biological control,Carabidae,intraguild predation,molecular gut content analyses,organic farming},
  language     = {eng},
  month        = {06},
  number       = {4},
  pages        = {1167--1177},
  publisher    = {Ecological Society of America},
  series       = {Ecological Applications},
  title        = {Diet of generalist predators reflects effects of cropping period and farming system on extra- and intraguild prey},
  url          = {http://dx.doi.org/10.1002/eap.1510},
  volume       = {27},
  year         = {2017},
}