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Effects of Changing Climate on Interactions Among Mountain Pine Beetle, Host Tree, and Microorganisms
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- Author / Creator
- Zaman, Rashaduz
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Environmental factors such as elevated levels of CO2 and O3 are increasingly affecting forest trees globally. Changes in climate have led to shifts in the geographic distribution of pests and pathogens associated with forests, with predictions of more native and invasive pests in the future. In North America, the mountain pine beetle (Dendroctonous ponderosae, (Hopkins), Coleoptera: Curculionidae, Scolytinae; MPB) poses a significant threat to lodgepole pine (Pinus contorta var. latifolia) forests, yet research on the impacts of climate change on MPB and its symbiotic organisms remains limited. Understanding the mechanisms involved in interactions between plants, herbivores, and pathogens is crucial for assessing the effects of invasive species in a changing climate. First, the study investigated how the fungal symbionts associated with MPB can detoxify host monoterpenes in live lodgepole pine trees and logs. Analysis revealed an increase in terpenes and oxygenated monoterpene concentrations following the fungal infection, suggesting a potential role of fungal symbionts in altering host defense chemistry and attracting MPB. Subsequent research explored the effects of two pathogenic fungal species, including Atropellis piniphila, causal agent of Atropellis canker, Cronartium harknessii, the causal agent of western gall rust, and three ophiostomatoid fungi (Grosmannia clavigera, Ophiostoma montium, and Leptographium longiclavatum) associated with MPB on the defense chemistry of mature lodgepole pine trees, highlighting distinct alterations in terpene chemistry and the importance of considering specific biotic stress agents in understanding tree susceptibility to insect attacks, particularly by MPB under changing environment. Furthermore, the study examined the impact of elevated ozone (eO3) concentrations on MPB physiology and behaviour, revealing a dose-dependent effect on mating success and offspring morphology and behaviour. To my surprise, while adaptive responses to oxidative stress were observed, including reduced respiration and
heightened locomotor activity, mating success was compromised due to the degradation of pheromone components. Intriguingly, transgenerational plasticity in offspring morphology and behaviour suggested potential stress resistance mechanisms, underscoring the sensitivity of MPB to eO3 concentrations and providing crucial insights into the ecological implications of such changes on insect populations. Additionally, controlled climate chamber experiments manipulating CO2, O3, and humidity levels revealed climate change-induced alterations in MPB reproduction, fungal growth, and immune responses, highlighting the significance of understanding the evolving relationships between forest pests and their symbiotic partners in a changing environment. Overall, these results contribute to understanding the complex interactions between bark beetles, fungi, host trees, and the changing climate. They emphasize the importance of considering both biotic and abiotic factors in developing effective strategies for resilient forest ecosystems amidst ongoing environmental changes. -
- Subjects / Keywords
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- Graduation date
- Fall 2024
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.