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Behavioural mechanisms behind aggregation in a tritrophic perspective

Stephan, Jörg (2016). Behavioural mechanisms behind aggregation in a tritrophic perspective. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2016:34
ISBN 978-91-576-8570-4
eISBN 978-91-576-8571-1
[Doctoral thesis]

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Gregarious organisms need to handle the trade-off between positive effects of group living and increasing food competition. The gregarious Phratora vulgatissima, a specialist leaf beetle on willow in Europe and Asia, frequently reaches outbreak densities in natural stands and short rotation coppices. Outbreaks threaten the yield and plantations therefore rely on omnivorous predators as biocontrol agents, like Anthocoris nemorum and Orthotylus marginalis. I aimed to elucidate behavioural mechanisms of the beetle and the predators to understand how and why species aggregate. The beetle’s aggregation behaviour was studied by looking at key reproductive traits like oviposition rate, clutch size, and oviposition site choice on willow shoots. Both predators were characterized further by examining where on the vertical shoot they preferentially hunt for the beetle’s eggs and how the quality of alternative food (different plant genotypes) alters their effects on the beetle. I so revealed how the reproduction of the beetle is modulated by lateral (conspecific density), bottom-up (plant genotypes), and top-down (omnivorous predators) effects. To lower exploitative competition among larvae females increase the distances between clutches on a plant and lower their oviposition rate if too many, or too few (too few confirmations of own decision) conspecifics visited a shoot. Observed bottom-up effects include lowering clutch size and number of eggs on a shoot with plant genotype unsuitability, initially selecting large leaves for oviposition/feeding, and increasing clutch distances due to larger leaf area of a willow genotype. Three top-down effects in form of predator avoidance behaviours were observed. Females lowered median clutch size and oviposition rate leading to fewer eggs in presence of the predators/their combination. Females also preferentially feed in the shoot canopy but oviposit in the lower part. In combination with the observation that both predators show contrasting vertical preferences on the shoot I argue that females try to avoid the area were the predators are consuming more eggs. In general I contributed to the ecological concept of habitat domain, attack-abatement, clutch size, cognitive maps, and nonconsumptive effects. I hope the results facilitate our understanding of insect outbreaks and species aggregation, possibly leading to better control of those in economic relevant systems.

Authors/Creators:Stephan, Jörg
Title:Behavioural mechanisms behind aggregation in a tritrophic perspective
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :2016
Depositing date:30 March 2016
Number of Pages:43
IStephan JG, Stenberg JA, Björkman C (2015). How far away is the next basket of eggs? Spatial memory and perceived cues shape aggregation patterns in a leaf beetle. Ecology 96(4), 908-914.
IIStephan JG, Low M, Stenberg JA, Björkman C (2016). Habitat quality and predator hunting mode interactively affect attack-abatement patterns of predation risk. Ecology (submitted).
IIIStephan JG, Stenberg JA, Björkman C. Consumptive and nonconsumptive effect ratio depends on local resource quality – a story about host plants, leaf beetles, and omnivorous predators (manuscript).
IVStephan JG, Stenberg JA, Björkman C. Moving up and down the shoot: how ovipositing leaf beetles avoid habitat domains of different predators (manuscript).
Place of Publication:Uppsala
Publisher:Department of Ecology, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-576-8570-4
ISBN for electronic version:978-91-576-8571-1
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:L Animal production > L20 Animal ecology
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Zoology
(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Ecology
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Agricultural Science
Agrovoc terms:coleoptera, chrysomelidae, anthocoris nemorum, hemiptera, oviposition, pest insects, habitats, predation, omnivores, animal ecology
Keywords:clutch size, cognitive map, kin recognition, non-consumptive effects, oviposition rate, neutral interference, selfish herd, habitat quality, dilution, omnivore
Permanent URL:
ID Code:13237
Faculty:S - Faculty of Forest Sciences
Department:(NL, NJ) > Dept. of Ecology
(S) > Dept. of Ecology
External funders:FORMAS and Future Forests and Swedish Energy Agency
Deposited By: Mr Jörg Stephan
Deposited On:31 Mar 2016 08:14
Metadata Last Modified:10 Sep 2020 13:41

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