REPRODUCTIVE-BIOLOGY OF A PRIMITIVE ANGIOSPERM, PSEUDOWINTERA-COLORATA (WINTERACEAE), AND THE EVOLUTION OF POLLINATION SYSTEMS IN THE ANTHOPHYTA

Stigmatic exudate-eating chironomid flies (Smittia) and pollen-eating halodid beetles are the most common visitors to flowers of Pseudowintera colorata. Plants are self-incompatible. After selfing pollen tubes penetrate the nucellus; chase pollination experiments show that the incompatibility reaction occurs before fertilization. When pollen is applied to stigmas, the exudate dries rapidly and does not usually reappear. A review of anthophytes suggests that their common ancestor around 200 mya was bisexual and pollinated at least in part by nectar-seeking insects, possibly including flies. The angiosperm stigma appears to have evolved from a pollination drop mechanism via an adaxial stigmatic surface.