Trait selection in flowering plants: how does sexual selection contribute?

By highlighting and merging the frameworks of sexual selection envisioned by Arnold (1994) and Murphy (1998), we discuss how sexual selection can occur in plants even though individuals do not directly interact. We review studies on traits that influence pollen export and receipt in a variety of hermaphroditic and gyrodioecious plants with the underlying premise that pollination dynamics influences mate acquisition. Most of the studies reviewed found that phenotypes that enhance pollen export are in harmony with those that enhance pollen receipt suggesting that in many cases pollinator visitation rates limit both male and female function. In contrast, fewer traits were under opposing selection; but when they were, the traits most often were associated with enhancing the specific aspects of a given sex function. Our review helps clarify and illustrate why sexual selection can be a component of trait evolution in hermaphrodite plants.