Exact tracking of pollen transfer and mating in plants

Abstract

UNLIKE animals, where individuals engage in direct sexual encounters, higher plants interact sexually only through minute, usually animal-mediated pollen grains, a trait that has hampered understanding of processes that govern plant evolution. A new technique using micro-tags to mark individual orchid pollinia and monitoring of all stigmas for pollination made it possible to measure exactly pollen transfer and mating pattern in a plant species. We report here that in populations of a hawkmoth-pollinated orchid, Aerangis ellisii, pollen transfers were found to be infrequent, to involve single pollen parents, and to occur mostly within 5 metres. Pollinator-mediated patterns of disproportional reproductive success suggest that floral traits are being shaped by mutual sexual selection as proposed by Darwin1–3. The microtag method opens an avenue for novel exploration of plant evolution.