The purpose of this research is to examine the geographic patterns of genetic variation in ponderosa pine and limber pine, with the goal of understanding how those geographic patterns were formed. This study takes advantage of unique patterns of inheritance in pines. Mitochondrial DNA (mtDNA) is inherited maternally and is dispersed only short distances in seeds. Chloroplast DNA (cpDNA) is inherited paternally, and has the potential to disperse great distances in wind-born pollen. Minimal gene flow of mtDNA allows it to detect genetic differences evolved between glacial refugia. High gene flow of cpDNA enables it to measure the degree of gene flow among populations. Sequence variation of mtDNA and cpDNA will be used to describe the variation across the ranges of both species.
Biologists have studied geographic variation of plants and animals for centuries, but advances in molecular techniques have dramatically increased the information that can be collected from natural populations, and advances in the treatment of the data have dramatically increased the information that can be extracted from the data. Analyses of mtDNA will allow us to look far back into history, to see how the waxing and waning of the glaciers pushed forests across the landscape. Analyses of cpDNA will reveal the extent of pollen flow, and allow us to determine whether different populations evolve independently, or whether gene flow binds populations together, as if the distances among them were an illusion.
