XVI International Botanical Congess

Our research documents the magnitude and genetic basis of inbreeding depression in two closely related taxa of Mimulus. M. guttatus has large bee-pollinated flowers, while M. micranthus is the small flowered primarily selfing derivative of M. guttatus. We demonstrate that inbreeding depression is present in both the primarily selfing and mixed-mating taxa, but its presence varies among traits and between species. The magnitude is consistently lower in the selfer compared to the mixed-mating taxon as predicted by theory. Dominance-based inbreeding depression plays a major role in the genetic basis of traits in both taxa. Genetic variation of inbreeding depression within populations may provide insight to the repeated evolution of selfing taxa from outcrossing taxa in the plant kingdom.