Environmental change has a wide range of ecological consequences, including species extinction and range expansion. Many studies have shown that insect species respond rapidly to climatic change. A mountain pine beetle epidemic of record size in North America has led to unprecedented mortality of lodgepole pine, and a significant range expansion to the northeast of its historic range. Our goal was to determine the spatial genetic variation found among outbreak population from which genetic structure, and dispersal patterns may be inferred. Beetles from 49 sampling locations throughout the outbreak area in western Canada were analysed at 13 microsatellite loci. We found significant north-south population structure as evidenced by: (i) Bayesian-based analyses, (ii) north-south genetic relationships and diversity gradients; and (iii) a lack of isolation-by-distance in the northernmost cluster. The north-south structure is proposed to have arisen from the processes of postglacial colonization as well as recent climate-driven changes in population dynamics. Our data support the hypothesis of multiple sources of origin for the outbreak and point to the need for population specific information to improve our understanding and management of outbreaks. The recent range expansion across the Rocky Mountains into the jack/lodgepole hybrid and pure jack pine zones of northern Alberta is consistent with a northern British Columbia origin. We detected no loss of genetic variability in these populations, indicating that the evolutionary potential of mountain pine beetle to adapt has not been reduced by founder events. This study illustrates a rapid range-wide response to the removal of climatic constraints, and the potential for range expansion of a regional population.

We isolated 16 polymorphic microsatellite loci in the mountain pine beetle (Dendroctonus ponderosae Hopkins) and developed conditions for amplifying these markers in four multiplex reactions. Three to 14 alleles were detected per locus across two sampled populations. Observed and expected heterozygosities ranged from 0.000 to 0.902 and from 0.100 to 0.830, respectively. Three loci deviated from Hardy-Weinberg equilibrium in one sampled population. One of these loci may be sex linked. These markers will be useful in the study of population structure in this important pest species.

The mountain pine beetle (MPB) is an eruptive insect that is currently causing an outbreak of record size in Western Canada. A lack of long distance MPB dispersal data has limited our understanding of and ability to manage MPB epidemics. My goal was to determine the MPBs Western Canadmn population structure. upon wh1ch d1spersal patterns may be supenmposed. I analyzed MPBs from 35 mfested lodgepole pine stands at six microsatellite loc1. The MPB exh1bited strong and s1gmticant Western Canadian population structure. Th1~ population ~tructure wa~ mcongruent w1th the structure of its primary symbiont. 0. £ hn igerwn. but congruent \\1 ith the structure of 1ts primary host, P.contorta. Novel fungal selection pres~ure~ ha"Ve probably caused the discrepancy in beetle/fungus phylogeography. A result of Western Canadmn MPB population structure alternately contrasts and supports population structure~ previou~ly reported for Scolytids, including MPBs. The partitioning of MPB populatiOn structure into a Northern and Southern group is most likely the result of postglacial recolonization and differences in MPB population dynamics. Primarily using my genetic data, I inferred the historical movement patterns of the MPB in Western Canada. I found no evidence that the epidemic spread from an epicenter in Tweedsmuir Provincial Park. My data support multiple sources for the current epidemic; I suggest that regional population expansions have caused the rapid escalation in the severity of the current epidemic. MPB movement patterns and atmospheric wind data were concordant; winds in Western Canada are predominantly westerly or southwesterly. which was the predominant direction of inferred movements amo ng MPB populations. In contrast, current MPB population structure best fits a 30-year climatic suitabi lity distribution for a historical as II opposed to the most current ( 1971 -2000) period. The population genetics of long distance MPB dispersal. an evolutionary theory for MPB population dynamics. and MPB "range expansion" are extensively d1scussed. Potential biases and research limitations are noted. Based on my results and inferences. future areas of investigation are noted.An executive summary. with management recommendations. is prov1ded as a conclusion.