Role of plant secondary compounds in invasion biology of an insect herbivore in novel habitats

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Jack pine is a dominant tree species in the Canadian boreal forest, providing essential services for a number of plant and animal species. However, its existence has been threatened by the invasive mountain pine beetle as it has killed millions of hectares of historical host trees, mainly lodgepole pine in Western North America during the last outbreak and recently invaded the western extend of jack pine forests in northern Alberta (Canada). Within its historical range, mountain pine beetle shares a long co-evolutionary history with lodgepole pine and has adapted to utilize its secondary compounds. However, it is unknown whether jack pine and lodgepole pine differ in their susceptibility to beetles as both species vary with respect to the composition of secondary compounds which could affect host tree-beetle interactions. In my application, I proposed to test two sets of objectives targeting two different aspects of mountain pine beetle invasion dynamics in the jack pine forests. Study 1 will integrate knowledge of biochemical and physiological mechanisms of jack pine resistance to a parasitic plant pathogen, dwarf mistletoe, and the mountain pine beetle and its symbiotic fungal pathogen and, in part, their relationship to the resource availability over different temporal and spatial scales. Study 2 will focus on the variation in chemical communication signals (pheromones) produced by the mountain pine beetle on jack pine across multiple generations as plant secondary compounds are required for pheromone production and aggregation by the bark beetles on the host trees. Information resulting from these studies will be important for both basic and applied understanding of mountain pine beetle invasion dynamics–and success–in the Canadian jack pine forests. Study 1 will advance plant defense theories while increasing understanding of factor regulating pathogen-herbivore relationships and insect outbreaks. This project also has important applied implications: Achieving a better understanding of the physiological and biochemical processes that influence the outcome of tree host-pathogen-insect interactions may guide strategies to improve tree performance in optimal and suboptimal environments through silvicultural prescription and genetic selection. Results of the study 2 will determine whether male and female mountain pine beetles can maintain chemical communication in the novel host system. Likewise, whether bark beetle attacks are synchronized to successfully colonize and kill jack pine trees could be important to determine the outbreak dynamics of the mountain pine beetle in the novel ecosystem. From a practical perspective, these results would be useful for the development of attractive baits (lures) to monitor and even control mountain pine beetle populations in the novel jack pine forests.