Oikos (2013) 122, 1768-1776

Lorenzo Marini, Åke Lindelöw, Anna Maria Jönsson, Sören Wulff and Leif Martin Schroeder (2013)
Population dynamics of the spruce bark beetle: a long-term study
Oikos 122 (12), 1768-1776
Abstract: Bark beetle population dynamics is thought to be primarily driven by bottom-up forces affecting insect performance and host tree resistance. Although there are theoretical predictions and empirical evidences that predation and parasitism may play an important role in driving bark beetle population fluctuations, long-term studies testing the role of both biotic and abiotic controls on population dynamics are still rare. The aim of the study was to quantify the relative importance of predation, negative density feedback and abiotic factors in driving Ips typographus population dynamics. We analyzed a unique time series of population density of I. typographus and its main predator Thanasimus formicarius over almost two decades in four regions across Sweden. We used a discrete population model and a multi-model inference approach to evaluate the importance of both bottom up and top down factors. We found that availability of breeding substrates in the form of storm-felled trees was the main outbreak trigger, while strong intra-specific competition for host trees was the main endogenous regulating factor. Although temperature-related metrics are known to have strong individual effect on I. typographus development and number of generations, they did not emerge as important drivers of population dynamics. A positive effect of low summer rainfall was evident only in the region located in the southernmost and warmest part of the spruce distribution range in Sweden. Predator density did not emerge as an important prey regulating factor. As the reported damage from storms seems to have increased across whole Europe, spruce forests are expected to be increasingly susceptible to large outbreaks of I. typographus with important economic and ecological consequences for boreal ecosystems. However, the observed negative density feedback seems to be a natural regulating mechanism that impedes a strong long-term propagation of the outbreaks.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
(original language: English)
Link to article at publishers website
Database assignments for author(s): Leif Martin Schroeder, Lorenzo Marini

Research topic(s) for pests/diseases/weeds:
population dynamics/ epidemiology
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
population dynamics/epizootiology

---

Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Ips typographus		Sweden
Thanasimus formicarius (predator)	Ips typographus		Sweden