Pollination biology of the endangered orchid Cypripedium japonicum in a fragmented forest of J apan

Pollination biology studies of the endangered orchid Cypripedium japonicu m were conducted in its natural habitat using pollinator observation and hand‐pollination experiments. The observed fruit set was as follows: artificial outcross‐pollinated, 100%; artificial self‐pollinated, 100%; pollinator‐excluded, 0%; and emasculated flowers, 0%. These results show that this species, although self‐compatible, is neither autogamous nor agamospermous. The fruit set for open‐pollinated flowers was 14.9%, which suggests that the study population was subject to pollinator limitation. The nectarless flowers of C. japonicum were exclusively visited and pollinated by the queens of two bumblebee species ( Bombus ardens and B. diversus diversus ). It is probable that the nectarless flowers of C. japonicum attract pollinators through a generalized food deceptive system.