Journal ArticleDOI
Regulation of aphid populations by aphidiid wasps: does parasitoid foraging behaviour or hyperparasitism limit impact?
Manfred Mackauer,Wolfgang Völkl +1 more
TLDR
It is proposed that a wasp's reproductive strategy, as opposed to hyperparasitism, is the dominant factor in aphidiid population dynamics, and that a parasitoid's potential to regulate the host population is largely determined by its foraging strategy.Abstract:
Aphidiid parasitoids (Hymenoptera: Aphidiidae) of aphids generally exploit only a small percentage of the available host resources in the field. This limited impact on aphid populations has often been explained as a consequence of hyperparasitism. We propose that a wasp's reproductive strategy, as opposed to hyperparasitism, is the dominant factor in aphidiid population dynamics. A wasp's foraging efficiency and oviposition decisions are influenced by several variables, including searching behaviour between and within patches, host choice (as modified by the aphids' defensive behaviours), and plant structural complexity. Two broadly different patterns of host exploitation have evolved in aphidiid wasps in relation to ant-aphid mutualism. Firstly, in species that are exposed to predation and hyperparasitism, a female may leave a patch before all suitable hosts are parasitized. Because predators and hyperparasitoids tend to aggregate at high aphid or aphidiid densities, or in response to aphid honeydew, this strategy enables females to reduce offspring mortality by “spreading the risk” over several host patches. Secondly, in species that have evolved mechanisms to avoid aggression by mutualistic ants, females are able to exploit a hyperparasitoid-free resource space. Such species may concentrate their eggs in only a few aphid colonies, which are thus heavily exploited. Although hyperparasitism of species in the first group tends to reach high levels, its overall impact on aphid-aphidiid population dynamics is probably limited by the low average fecundity of most hyperparasitoids. We discuss the foraging patterns of aphidiid wasps in relation to aphid population regulation in general, and to classical biological control in particular. We argue that a parasitoid's potential to regulate the host population is largely determined by its foraging strategy. In an exotic parasitoid, a behavioural syndrome that has evolved and presumably is adaptive in a more diverse (native) environment may, in a more uniform (managed) environment, result in suboptimal patch-leaving and oviposition decisions, and possibly increased resource usage.read more
Citations
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Journal ArticleDOI
Higher-order predators and the regulation of insect herbivore populations
TL;DR: The hypothesis that higher-order predators may constrain the top-down control of herbivore populations is evaluated and manipulative field experiments will be especially valuable in furthering the understanding of their roles in arthropod communities.
Journal ArticleDOI
Risk-spreading and bet-hedging in insect population biology.
TL;DR: Although there is evidence for risk-spreading, particularly in facultative diapause, I have been unable to find any definitive tests with unequivocal results showing that risk- Spreading has been a major factor in the evolution of insect behaviors or life histories.
Journal ArticleDOI
The structure of an aphid–parasitoid community
TL;DR: Mummy parasitoids were the most important group linking different aphids, and common aphid species shared few strong, indirect links via primary parasitoid or hyperparasitoids, but could be strongly linked by mummy Parasitoids.
Journal ArticleDOI
Ecology and evolution of aphid-ant interactions
TL;DR: This review uses aphid-ant interactions to illustrate the whole range of interactions from antagonistic to mutualistic as well as to identify the processes affecting the degree of association and in particular the context within which such interactions evolved.
Journal ArticleDOI
Intraguild interactions in aphid parasitoids.
Jacques Brodeur,Jay A. Rosenheim +1 more
TL;DR: It is concluded that intraguild interactions have a primary effect in driving fluctuations in aphid parasitoid populations and can substantially alter the effectiveness of aphid Parasitoids as biological‐control agents.
References
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Journal ArticleDOI
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Temperature requirements of some aphids and their parasites
TL;DR: Differences between the developmental thresholds and temperature requirements of A cyrtihosiphon pisum (Harris), Aphis craccivora Koch, Brevicoryne brassicae (L.), Macrosiphum avenae (F.), and Masonaphis maxima (Mason) (Homoptera: Aphididae); their parasites
Journal ArticleDOI
Foraging for Patchily-Distributed Hosts by the Parasitoid, Nemeritis canescens
TL;DR: The locomotory responses which influence patch time allocation were investigated for the parasitoid, Nemeritis canescens (Grav.).