Tree Diameter Effects on Mountain Pine Beetle Success
Date
2018-06-15
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Abstract
Habitat-seeking dispersers are faced with the challenge of finding high quality habitats while minimizing the costs incurred during habitat selection; dispersers can facilitate habitat selection by using cues emitted by their habitat. Here I investigate the habitat selection of the mountain pine beetle (MPB, Dendroctonus ponderosae), a pest insect which kills large lodgepole pine (Pinus contorta) trees during outbreaks. I measured host quality traits (phloem thickness and defensive traits) with respect to tree size as well as MPB attack and brood production. I also tested MPB orientation to two host size treatments by using baited funnel traps. Larger trees tended to be better MPB hosts. Larger trees had thick phloem and fewer to neutral defences compared to smaller trees. Larger trees were more likely to be attacked and sustained more attacks while smaller trees were nearly unattacked. After accounting for tree size, there was no evidence that MPB preferentially attacked trees with the thickest phloem or fewest defences which suggests that MPB attack the most detectable hosts rather than the highest quality hosts. Absolute brood production showed a hump-shaped relationship to tree size, suggesting that large trees may not necessarily benefit MPB offspring. More MPB were caught in large-diameter traps than small-diameter traps; however, this only occurred when the traps were paired. When traps were independent, the mean catch of both treatments was approximately equal. This work shows that larger trees tend to be better hosts for MPB but MPB do not appear to preferentially orient to large silhouettes, suggesting that visual host size information is a minor component of MPB host selection behaviour.
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Keywords
Mountain pine beetle, lodgepole pine, forest ecology, habitat selection, tree physiology, insect behaviour
Citation
Murphy, W. A. (2018). Tree Diameter Effects on Mountain Pine Beetle Success (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/32004