Pollen Dispersal in Natural Populations: A Method for Tracking Individual Pollen Grains

Abstract

Pollen dispersal studies in natural populations have been significantly hampered by the lack of a technique providing effective pollen labeling. Such a method has been developed which utilizes 14C labeling of pollen in the anther fol- lowed by identification of individual labeled grains using thick layer liquid emulsion autoradiography. This provides a safe, inexpensive and highly sensitive method of tracking individual pollen grains between plants or from plant to pollinator, etc., in natural populations. Pollen dispersal in natural populations is a poorly understood phe- nomenon in spite of its fundamental importance in the population bi- ology of plants. Four major types of techniques have been used to mea- sure pollen dispersal and all appear to have significant limitations as currently applied. One approach utilizes naturally occurring variation in pollen morphology to identify pollen. Sufficient natural variation in pol- len is uncommon within or between closely related species and relatively few studies have been able to use this straightforward approach. A sec- ond method of tracing pollen movement requires observation of pollen vectors (e.g., Levin et al., 1971). However, in many cases the vectors are