The evolution and adaptive significance of heterostyly.

The origin and adaptive significance of heterostylous breeding systems have fascinated evolutionary biologists since Darwin's early work on the subject. Models of the evolution of heterostyly differ in the emphasis given to different selective forces and in the sequence in which the physiological and morphological components of the polymorphism are thought to arise. Recent field studies of the population biology of heterostylous plants provide support for Darwin's hypothesis that the style-stamen polymorphism promotes disassortative pollination among the floral morphs.