This study investigates the factors maintaining a spatially discrete flower color polymorphism between coastal and inland populations of southern California Mimulus aurantiacus. Coastal populations contain exclusively red flowers, while approximately 30 km from the coast there is an abrupt transition to yellow flowers. This pattern makes M. aurantiacus an extremely interesting system for investigating whether this polymorphism has been influenced by historical barriers to gene flow or whether (and how) natural selection has shaped it. We will use a combination of molecular genetics, field observations, and experimental studies to examine the degree of morphological, geographical, and genetic differentiation between these morphs while attempting to describe the relative roles of pollinator versus non-pollinator selection on the maintenance of this polymorphism.
This research program will be important for increasing our understanding of the forces maintaining trait variation in nature. Preliminary results implicate a strong role for natural selection in preserving this polymorphism, but the selective forces remain unclear. Proposed field and laboratory work will include the assistance of many undergraduate researchers. Their involvement in these studies is crucial to its success and provides for enhanced educational experiences.
