Click a leaf

 

The evolution of phenotypic plasticity: Plastic responses to canopy shade in jewelweed

Past research with Johanna Schmitt at Brown University concerned the evolution of plant responses to vegetation shade using Impatiens capensis, a model system for studying phenotypic plasticity in plants. This research addressed the adaptive value, quantitative genetic basis, and mechanistic basis of this plastic response. Field selection studies of plastic responses to vegetation shade tested for local adaptation and population differentiation in plastic responses to overhead canopy. Not only did populations display different degrees of plasticity, but selection on the plastic response also differed between the native sites of those populations in a direction consistent with the hypothesis of adaptive divergence in plasticity.

Quantitative genetic studies have identified genetic constraints on the evolution of plastic responses to canopy shade and have revealed environment-dependent population divergence in genetic variance-covariance relationships among plastic characters. They also determined that responses of some characters are strongly mediated by the photoreceptors, phytochrome, whereas responses of others are not.

Continuing studies of the adaptive value and genetic basis of phenotypic plasticity are being conducted in this lab within a slightly different context; namely that of parental effects on seed characters such as dispersal and germination. Parental effects can be considered a form of cross-generational plasticity whereby the parental environment influences progeny phentoype. Similar tools of quantitative genetic analysis that were used in these studies are being applied to investigate the evolution of parental effects.

Click a leaf