Floral Integration, Modularity, and Accuracy: Distinguishing Complex Adaptations from Genetic Constraints

Abstract The origin of flowers is clearly one of the most important “key innovations” in the history of plant evolution. In addition to representing a number of functional advancements over the reproductive structures of nonflowering plants, flowers are modular organs that usually express limited variation within populations and yet huge variation among species and higher taxa. This variation in floral traits has fascinated evolutionary biologists since at least Darwin’s time. Because flowers are highly evolved structures that interact in complex but analyzable ways with pollinators, they make ideal study systems for the evolutionary analysis of morphology, integration, and modularity. In this chapter we address the functional significance of floral integration and modularity, focusing particularly on the role of integration in the evolution of accuracy and precision of pollination, as compared across three different study systems.