Graduation Date



Shifts in species distributions caused by climatic oscillations may lead to geographic isolation of populations and fewer opportunities for genetic exchange among locations. Examining trends in genetic relationships among stonefly populations can help us predict how organisms might respond to environmental changes. Prior work established that isolated montane populations of the stonefly Doroneuria baumanni had high levels of genetic structure within the Great Basin and that this diversification occurred during the Pleistocene. This differentiation may have resulted from historical climatic oscillations. With this in mind, we evaluated the contemporary genetic structure of another Great Basin stonefly, Hesperoperla pacifica. Because H. pacifica has relatively broader habitat requirements, we predicted its populations would display less genetic structure than those of D. baumanni. We estimated genetic differentiation among and within 12 populations of H. pacifica using 568 base pairs of the mitochondrial gene cytochrome b gene. FST estimates indicate that H. pacifica populations are less structured than D. baumanni, which had showed deep levels of divergence across limited geographic distances. These results confirm the benefits of a comparative approach to understanding the phylogeography and population genetic structure of stoneflies of the Great Basin.