VOLES, MOLARS, AND MOLECULES: INTEGRATING QUANTITATIVE MORPHOLOGY, GENETICS, AND EVO-DEVO TO STUDY EVOLUTIONARY PROCESSES

One of the overarching goals of paleobiologists is to utilize the fossil record to understand evolutionary processes. The fossil record of the Quaternary of North America is among the best records for this use, by virtue of its density and the fact that many organisms found within it are still extant. This is the case with the Sagebrush Vole, Lemmiscus curtatus, which has an extensive fossil record extending back approximately two million years and a broad extant geographic distribution. In addition to its geologic and geographic distributions, it appears that L. curtatus has undergone an evolutionary transition, characterized by the addition of cusps on its lower first molar (m1). The addition of cusps appears, in the fossil record, to happen in multiple localities at similar times, within the last two million years. Yet the mechanism(s) which produced these morphological shifts are unknown. Here, I present a comprehensive study of the Sagebrush Vole across its spatiotemporal range, including quantitative assessment of m1 variation, genetic assessment of extant population structure, and modeling of embryological development, to demonstrate how evolution in L. curtatus occurred over the past two million years. Importantly, the end result, not only demonstrates how L. curtatus has evolved, but demonstrates how researchers can integrate across hierarchical levels of biology to more completely understand how evolution proceeds.