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 Darwin^1–3. The microtag method opens an avenue for novel exploration of plant evolution.