Using a native plant-pathogen system as a model to investigate success of the invasive mountain pine beetle in jack pine

• Author / Creator

  Klutsch, Jennifer G.

• Tree-infesting organisms have recently expanded their ranges into many novel habitats where they will not only interact with new host tree species, but also with a myriad of other organisms that also share these hosts. Understanding the major factors and mechanisms that mediate plant-herbivore-pathogen interactions, such as plant defenses, will be important for determining the impact of invading organisms. My research investigates the range expansion of mountain pine beetle (Dendroctonus ponderosae (Hopkins), Coleoptera: Curculionidae, Scolytinae) into the novel host jack pine (Pinus banksiana Lamb.), which is an ecologically and economically important component of the Canadian boreal forest. First, I assessed the effects of drought on induced plant defense responses in jack pine to phytohormones (as a proxy for different classes of biotic disturbances) and a pathogenic fungal associate of mountain pine beetle, Grosmannia clavigera (Robinson-Jeffrey & Davidson). Prior induction from phytohormones resulted in systemic cross-induction of resistance to G. clavigera under normal watering treatment, but susceptibility under low watering treatment. Next, I identified the impact of multiple classes of induced host defense compounds due to the infection by a widespread native parasitic plant (dwarf mistletoe, Arceuthobium americanum Nutt. ex Engelm.) on the success of mountain pine beetle and G. clavigera. Systemically, there was a non-linear effect of dwarf mistletoe infection on monoterpenes, with increasing concentrations of monoterpenes at moderate severities and decreasing concentrations at high severities. Dwarf mistletoe-induced changes in monoterpenes seem to result in the systemic induced resistance as trees with moderate mistletoe severity were most resistant to G. clavigera. In contrast, phenolic compounds increased in amount with greater dwarf mistletoe infection severity but decreased after inoculation with G. clavigera. This inverse response to infection between monoterpenes and phenolics suggests that phenolics are detoxified by the fungus or there are tradeoffs between these two major defense classes. Furthermore, dwarf mistletoe-induced changes in defensive and physical characteristics reduced the competitive advantage of the subcortical insect community on mountain pine beetle performance. Tree-mediated interactions between biotic disturbances, such as dwarf mistletoe, and G. clavigera may impact mountain pine beetle establishment or maintenance in novel jack pine forests through systemic effects and coordination of defense chemicals.

• Subjects / Keywords

  • Plant defense
  • Plant-mediated interactions
  • Dwarf mistletoe

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3WM1475Q

• License

  This thesis is made available by the University of Alberta Libraries 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.