RUVINSKY, JESSICA* AND DAVID ACKERLY. Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020. - Adaptive phenotypic plasticity in Mimulus guttatus.
Physiology and morphology of Mimulus guttatus vary with water
level. Under flooded conditions, root to shoot ratio is significantly
higher and photosynthetic rate and conductance are significantly lower
than at field capacity. Is this phenotypic plasticity adaptive? Plants
were grown from seed in the greenhouse under two water levels. At 5, 7
and 10 weeks from emergence, a subset of the plants was switched into
the other environment (high water into low water and vice versa). The
third switch resulted in a crossover in fitness between the switched
and control plants: within each environment, the plants whose early
environmental cues corresponded to their ultimate environment had a
higher fitness than those responding to “incorrect” early cues. This
provides evidence that plasticity in response to water level is
adaptive in this species. The time courses of root to shoot ratio,
leaf area ratio, specific leaf area, reproductive allocation, maximum
photosynthetic rate and instantaneous water use efficiency were
followed, and fitness responses are interpreted in terms of changes in
these traits over time.
Key words: adaptive phenotypic plasticity, flood tolerance, Mimulus guttatus