Genetic structure of phylophagous insects are formed under many factors, such as co-evolutionary effect with hosts, geographic distribution, or migration which is impacted by climatic fluctuations or natural disturbances. To investigate the impact of 2003 pinyon pine beetle outbreak on its genetic structure, we sampled in total 244 individuals from 28 populations across six states in Southwest of United States in 2001 and 2003, constructed a phylogenetic tree, compared genetic diversity within each populations before and during outbreak, calculated genetic differentiation among populations, tested genetic variations on different hierarchical levels, and performed mantel tests to test isolation-by-distance. The diversity analysis and haplotype network did not demonstrate significant differences among populations before and during outbreak. Thus the outbreak had little impact on the genetic structure of Ips confusus. Spatial patterns of haplotype distribution, diversity trend, AMOVA and Mantel tests indicated that the genetic structure was closely associated with geography. These results suggest that multiple short-distance dispersals among proximal populations rather than dispersal among distant populations, have shaped the genetic structure of I. confusus despite greater potential for long distant dispersal during outbreaks.
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