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Food-web interactions and population variability of leaf beetles in managed and natural willow stands

Dalin, Peter (2004). Food-web interactions and population variability of leaf beetles in managed and natural willow stands. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae. Silvestria, 1401-6230 ; 303
ISBN 91-576-6537-0
[Doctoral thesis]

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It is generally believed that diversity leads to stability in ecological systems. One consequence would be that insect outbreaks (i.e. drastic increases in insect density) should be more frequent in managed systems, such as forest plantations and crop fields, than in natural and more diverse systems. The leaf beetle Phratora vulgatissima is a major insect pest in plantations of the willow Salix viminalis (‘energy forests’) and outbreaks are frequently observed. In this thesis, food-web interactions and population fluctuations of leaf beetles are compared between managed (Salix viminalis) and natural (S. cinerea) willow stands. In a five-year study, we found no difference in temporal variability of leaf beetle populations between managed and natural willow stands. However, drastic increases in leaf beetle density (‘outbreaks’) tended to be more frequent in managed stands. The two willow species studied responded differently to leaf beetle attack. The natural willow (S. cinerea) responded to grazing by adult beetles by producing new leaves with an increased density of trichomes (leaf hairs). Larvae were shown deterred from feeding on the induced leaves. This type of plant response may reduce the overall damage done by leaf beetles. However, no induced defence in response to adult grazing could be detected for the willow used in plantations, S. viminalis. Among the main predators attacking egg aggregations laid by leaf beetles, one type (mirid bugs) often stay and consume most eggs before moving on to search for other prey, a behaviour characterised as ‘find and stay’. Another type (anthocorid bugs) have more of a ‘run and eat’ behaviour; they visit many aggregations but consume fewer eggs within aggregations than mirids. In a simulation model, populations of leaf beetles were less likely to establish and to increase in abundance when attacked by ‘find and stay’ predators than when attacked by ‘run and eat’ predators. In the field, the leaf beetle P. vulgatissima occurred at low densities, and the predation on eggs was high, in natural willow stands where ‘find and stay’ mirids were abundant. The results suggest that a high abundance of heteropteran predators may prevent outbreaks of the leaf beetle P. vulgatissima.

Authors/Creators:Dalin, Peter
Title:Food-web interactions and population variability of leaf beetles in managed and natural willow stands
Series Name/Journal:Acta Universitatis Agriculturae Sueciae. Silvestria
Year of publishing :May 2004
Number of Pages:25
ALLI. Dalin P. & Björkman C. 2003. Adult beetle grazing induces willow trichome defence against subsequent larval feeding. Oecologia 134, 112-118. Erratum: Oecologia 134, 554. II. Dalin P., Björkman C. & Eklund K. 2004. Leaf beetle grazing does not induce willow trichome defence in the coppicing willow Salix viminalis. Agricultural and forest entomology, 6, 105-109. III. Dalin P., Kindvall O. & Björkman C. Effects of generalist predator feeding habits on prey population dynamics. Manuscript. IV. Dalin P. Habitat difference in willow leaf beetle abundance: plant quality or natural enemies? Manuscript. V. Dalin P., Björkman C. & Kindvall O. Population variability of leaf beetles in managed and natural willow stands. Manuscript.
Place of Publication:Uppsala
ISBN for printed version:91-576-6537-0
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:F Plant production > F40 Plant ecology
H Protection of plants and stored products > H10 Pests of plants
Subjects:Not in use, please see Agris categories
Agrovoc terms:chrysomelidae, salix viminalis, biodiversity, pest insects, predation, miridae, anthocoridae, trichomes, plant response
Keywords:diversity, stability, Chrysomelidae, induced plant responses, trichomes, predation, Heteroptera, Miridae, Anthocoridae
Permanent URL:
ID Code:559
Department:(NL, NJ) > Dept. of Entomology (until 061231)
Deposited By: Peter Dalin
Deposited On:13 May 2004 00:00
Metadata Last Modified:02 Dec 2014 10:05

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