Spread and impact of an eruptive herbivore in a novel habitat : consequences of climate change-induced range expansion

The Mountain Pine Beetle (MPB) has now affected more than 16 million hectares of forest in western Canada causing significant economic, social and ecological impact to the provinces of British Columbia and Alberta. Recent findings suggest that pine trees lacking historical exposure to MPB impacts are evolutionary naive, resulting in unprecedented impacts in previously unoccupied areas. MPB can also reproduce successfully in jack pine, the most abundant species of Pinus in the boreal forest which provides a potential conduit for further range expansion eastwards. Current understanding of MPB outbreak dynamics is based largely on research from its original habitat in lodgepole pine. As MPB expand their range, population dynamics are expected to differ from that of the originating habitat due to novel trophic interactions. I assessed the speculation that tree depletion by MPB in novel pine habitat is more severe than in evolutionarily experienced habitat. I utilized a landscape-level analysis of MPB infestation data across BC in relation to forest characteristics and climatic suitability. This required the use of several different data sources including a climate suitability model, province wide vegetation inventory and annual aerial overview survey data. Additionally I evaluated how potential host availability varies across the boreal forest of Canada and how this affects rates of spread under varying levels of climatic suitability and host susceptibility. Habitats only recently invaded by the MPB experienced impacts that were 1.7 to 3.9 times greater than those with long-term exposure to MPB impacts. Predicted MPB spread was rapid under conditions of high climatic suitability. Only under conditions of both low climate suitability and low host susceptibility did host availability limit spread. The challenge to forest management is large given the recently documented changes to insect population dynamics in naive environments. Priority should be given to the development of predictive tools supporting strategic landscape planning intent on minimizing additional impacts to naive ecosystems into the future. Despite continued uncertainty as to community and ecosystem trajectories under global change, this thesis exposes a coherent pattern of ecological change across a broad system at two distinct spatial scales.Forestry, Faculty ofGraduat