DUDASH, MICHELE R.1*, COURTNEY J. MURREN1, and DAVID E. CARR2. 1Department of Biology, University of Maryland, College Park, MD 20742; 2Blandy Experimental Farm, University of Virginia, Boyce, VA 22620. - Explorations into inbreeding depression, phenotypic plasticity, and their potential roles in colonization success.
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