Setting the stage: Phenotypic plasticity as habitat selection

The ability of plants to sense their environment gives them the capacity to respond to it plastically. Plastic responses, in turn, frequently alter the environment that plants experience. Plants can modify the environment they experience through many mechanisms-some approximate but others quite precise. The ability of plants to modify the environment they experience can strongly influence the evolution of characters expressed subsequently. A review of some theoretical models of habitat selection and of the coevolution of characters and their environments highlights the importance of habitat selection in plants. Novel evolutionary trajectories and outcomes result when organisms are capable of modifying the environment they experience. Specifically, characters can evolve even if they have no genetic variation, and plasticity in environment-determining characters may promote specialization in others. Divergence and reproductive isolation may even be augmented by habitat-selecting behavior in plants. An understanding of basic character evolution and the evolution of plasticity in plants requires an appreciation of the ability of plants to modify the environment they experience.