According to the geographic mosaic theory of coevolution (Thompson 2005), the potential for coevolutionary relationships between interacting species varies with the presence of other species within a community. This implies that the strength of coevolution between two species may vary geographically. In this study, we ask whether there is a shift in vertebrate seed dispersers between core range and peripheral populations in two related five-needle white pines, limber (Pinus flexilis) and southwestern white (P. strobiformis). In the Rocky Mountains, limber pine ranges from southern British Columbia and Alberta south to New Mexico. Southwestern white pine ranges through the higher mountains of northern Mexico north to southern Colorado and Utah, and northern Arizona. The pines overlap in southern Colorado, southern Utah, northern New Mexico, and northern Arizona.