Rodents are more diverse and abundant than any other mammal group. Although their success has been linked to an upper and lower pair of ever-growing incisors, little is known about the evolutionary relationship between incisor shape and behavior (ex. diet) in these animals. This study will examine incisor shape in fossil and living beavers with respect to the evolution of wood-cutting. Wood-cutting is of particular interest because wood is extremely tough and it might be expected that rodents that frequently cut wood should exhibit incisors specialized for that behavior. Both living species of beaver are similar in appearance and cut wood extensively. Fossil beavers, however, are a more diverse group. For example, they ranged in size from squirrel to black-bear size. Some used their incisor for digging. They also possessed a diversity of incisor shapes. In fact, one beaver that is known to have cut wood has incisors that differ in shape from those of the living beaver. What is the behavioral and evolutionary significance of these differently shaped incisors with respect to the evolution of wood-cutting? This question will be answered by reconstructing the evolutionary relationships among beavers, studying the relationship between incisor-shape, behavior and body-size in living rodents. The PI will also examine microscopic tooth-wear features as these might help determine how rodents incisors function. This research will serve to further our understanding of the evolutionary relationship between animal form and environment. Beavers are of particular interest in this regard because they have an unusually large impact on the structure and possibly the evolution of ecosystems.
