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Doctoral thesis, 2015

Omnivore population dynamics and trophic behavior

Liman, Anna-Sara


Plant traits can mediate the interactions between plant feeding trophic omnivores and their herbivore prey via density effects and by altering the omnivore’s trophic behavior (plant vs. prey feeding). These bottom-up effects can be important for our mechanistic understanding of omnivory as a stabilizing feature of food-webs, but can also be applied in management for conservation biological control. This thesis investigates how plant nutrient status influence heteropteran omnivore population dynamics and trophic behavior and explores management solutions for conservation biological control that can reduce the risk of leaf beetle outbreaks in willow short rotation coppice. The results provide novel empirical support for the established assumption that plant feeding can decouple omnivores from fluctuations in their prey populations. Plant feeding stabilizes omnivore population dynamics, which may explain why omnivore populations show no numeric response to fluctuations in leaf beetle population densities. The potentially strong omnivore-plant coupling suggests that omnivores can function effectively at low prey densities (contrary to specialist predators) to provide what has been referred to as ‘background level’ control of insect pests. The applied part of the thesis demonstrates that retaining willow refuges to reduce omnivore mortality and stabilize population densities across harvests increase rather than decrease the risk of leaf beetle outbreaks. The results also reveal that willow stands surrounded by landscapes with high proportion open land cover are less likely to experience leaf beetle outbreaks. This outcome was expected partly because of the recorded high and stable densities of heteropteran omnivores on high nutrient status host plants in agriculture dominated landscapes. In addition, the results illustrate that landscape-moderated recolonization after disturbance can change over time and that considering the temporal dynamics of populations may be crucial when designing and evaluating studies at landscape level. In conclusion, this thesis highlights the importance of basic ecological knowledge of predator trophic behavior for developing successful conservation biological control.


trophic omnivore; population dynamics; stability; trophic behavior; time series; recolonization; landscape; leaf beetle; willow short rotation coppice

Published in

Acta Universitatis Agriculturae Sueciae
2015, number: 2015:43
ISBN: 978-91-576-8284-0, eISBN: 978-91-576-8285-7
Publisher: Department of Ecology, Swedish University of Agricultural Sciences

Authors' information

Liman, Anna-Sara
Swedish University of Agricultural Sciences, Department of Ecology

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