TML> Dudash, Michele R.*, Courtney J. Murren, and David E. Carr. Mimulus guttatus has become a model system for the study of mating system evolution in the last two decades. We now know that the mixed-mating M. guttatus experiences significant inbreeding depression following one-generation and serial hand-self pollinations. The genetic basis of inbreeding depression is due to selection against deleterious alleles and not likely due to overdominance. Mimulus guttatus has also been used to examine the genetic basis of phenotypic plasticity. Both vegetative and reproductive characters respond to natural environmental gradients as well as experimentally imposed temperature and light regimes. Thus significant maternal effects have been found for the expression of both inbreeding depression and phenotypic plasticity. For example, there is evidence that flower number is correlated with inbreeding depression and also responds plastically to variable environments. This observation suggests that mating system variation may play an important role in the establishment of new populations. Recently established populations in new local areas and new distant geographic locations frequently contain only a fraction of the genetic variation present in the source population. In addition seed may come from populations that differ in degree of habitat heterogeneity and outcrossing. The goal of our ongoing work is to examine the relationship between inbreeding level and expression of phenotypic plasticity among maternal families and how these genetic components influence colonizing ability in native and novel geographic locations. To this end we will be examining the interaction between phenotypic plasticity and inbreeding in the context of ecological variation. The ecological and genetic history of a population may influence both the expression of phenotypic plasticity and inbreeding depression and together their interaction may have a direct impact on the potential for mating system evolution and colonizing success in nature.

Key words: colonization, inbreeding depression, mating system evolution, Mimulus guttatus, phenotypic plasticity