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Spatial characteristics of volatile communication and the role of soil resources in pine defenses
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- Author / Creator
- Hussain, Altaf
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Recent unprecedented climate change has increased the frequency and severity of tree-killing Dendroctonus bark beetles (Coleoptera: Curculionidae, Scolytinae). Understanding factors and mechanisms influencing host plant-bark beetle interactions at a landscape level such as plant defenses, edaphic conditions, plant nutrients, and plant-plant interactions will be important to determine the impact of bark beetle outbreaks and tracking their invasion success. I studied the range expansion of mountain pine beetle (Dendroctonus ponderosae Hopkins; MPB) into the novel host jack pine (Pinus banksiana Lamb.) in the boreal forest of western Canada. I investigated the effect of soil moisture on the existence of gradients in the chemical defenses along jack pine stems by using a MPB associated phytopathogenic fungus, Grosmannia clavigera. I further tested whether soil moisture gradients can affect non-structural carbohydrate (NSC) mobilization and allocation to two main classes of chemical defenses in jack pine, monoterpenes and diterpene resin acids. I found that constitutive NSC production increased with stem height, diterpene resin acid concentrations decreased, and monoterpene concentrations did not vary. With increasing soil moisture, NSC production decreased, monoterpene concentrations increased, and diterpene resin acid concentrations did not vary. At an induced level, trees on the sites with higher soil moisture developed smaller necrotic lesions and had higher monoterpene concentrations by mobilizing local NSC reserves. Diterpene resin acid concentrations did not vary with soil moisture but differed at each stem height. I also compared MPB host acceptance and brood production in jack pine cut bolts from trees on sites with different soil moisture, and nutrient concentrations. Host acceptance and brood production were greater in bolts from the site with lower soil moisture and higher phloem nitrogen concentration.
Finally, I tested whether pines interact and cooperate by using volatile defense compounds, and whether such interactions correlate with the spatial characteristics of sites, and tree attributes. I studied the constitutive and induced responses in non-attacked lodgepole pines within 30 m radii of pines attacked by MPB. I found that pines interacted with chemotypically related trees only. These results suggest that pines discriminate between volatile cues from kin and strangers, and the emitters likely aid only chemotypically related pines by emitting specific blends of volatiles that can only be deciphered by the receiving kin. -
- Graduation date
- Fall 2019
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.