Inducible nicotine production in native Nicotiana as an example of adaptive phenotypic plasticity

Nicotine, an inducible defense in a number of Nicotiana species, exemplifies adaptive phenotypic plasticity. The mechanisms responsible for its production are reviewed, and the induced character states are characterized allometrically in order to understand how inducibility changes over ontogeny responds to environmental variables that influence plant growth, and to relate inducible production to plant fitness correlates. The empirical evidence for fitness costs and benefits of inducible nicotine production are considered, and the physiological and ecological mechanisms potentially responsible for the costs are considered. An intimate understanding of the plant's natural history is an essential prerequisite to understanding these costs and benefits. Inducible nicotine production is just one of many traits that are altered after herbivore attack, and the cost-benefit model provides a valuable heuristic framework in which to understand the selective factors responsible for the maintenance of inducibly expressed traits.