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The southern pine beetle (SPB) is a small, black beetle that parasitizes pine trees across the United States and Central America. Recently it has been recognized that the range of SPB is not limited to the southern United States, but rather extends northward across the eastern United States, which raises concerns for pine trees that have never encountered the pest before. Using mitochondrial DNA sequences from a section of the cytochrome oxidase I gene and four different measures of genetic distance compared to geographic distance, we tested for evidence of isolation by distance (IBD) among sampled SPB to see whether this range expansion was recent, and thus showed no evidence of IBD, or relatively old, such that there would be a positive relationship between genetic and geographic distance. We found that there was only one, possibly erroneous, statistically significant IBD relationship, and surprisingly, it was negative, which suggested a lack of IBD that could possibly be explained by human interference. When comparing two measures of genetic distance that are informative over different time scales (FST and ΦST), it was discovered that the population genetic structure, though weak, is likely quite old.
Holman, Lora Grace, "Invasion of the Northeastern United States by the Southern Pine Beetle, Dendroctonus Frontalis, and the Impacts on Signatures of Isolation by Distance Assessed using Mitochondrial DNA" (2022). Honors Theses. 2607.
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