Pollination biology of a rare serpentine plant, Japonolirion osense (Petrosaviaceae)

Petrosaviales is an early diverging monocot order that includes only two genera with distinct nutritional modes, namely the autotrophic Japonolirion and mycoheterotrophic Petrosavia. A rare serpentine plant endemic to Japan, Japonolirion osense is the only species of this genus. Although Petrosavia species are known to produce seeds by autonomous self-pollination, the mating system and flower visitors of J. osense remain unknown. In this study, the pollination biology of J. osense was investigated on a serpentine slope in northern Hokkaido, Japan. Pollination experiments suggested that J. osense predominantly depends on cross-pollination by insect pollinators for seed production. Ants and dipterans were the main flower visitors to this species. This study showed that the two genera in Petrosaviales with distinct nutritional modes also have contrasting mating systems, which provides insights into the evolution of pollination biology in this early diverging monocot order.