GALLOWAY, LAURA F. Department of Biology, University of Virginia, Charlottesville, VA 22904. - Plasticity of sex allocation in Mimulus guttatus: comparisons among ecologically different populations.
Within the genus Mimulus, predominantly selfing species tend to
be found in habitats where water is ephemeral and outcrossing taxa
where water is more persistent. Populations of Mimulus guttatus
also inhabit sites that vary in the persistence of soil moisture.
Individual allocation to sexual reproduction and vegetative
propagation varies among populations in concert with local patterns of
water persistence. Mating system may vary among these ecologically
differentiated populations. Selection for reproductive assurance is
likely to be greater in populations that experience ephemeral soil
moisture and reproduce only through seed. In addition the plastic
response to water of traits that influence mating system and
reproductive assurance, is predicted to vary among populations that
differ in water availability. I found that water availability
influences flower size and pollen and ovule production under
greenhouse conditions. In addition, autofertility and the distance
between the anthers and the stigma vary with moisture level. While
these traits vary among populations, their change in response to water
availability is similar. These results suggest that environmental
variation influences mating system and autofertility in Mimulus
guttatus. In addition, populations appear to retain the ability to
make similar adjustments to environmental variables despite underlying
divergent reproductive patterns.
Key words: autofertility, floral traits, mating system, Mimulus guttatus, phenotypic plasticity