Pollination ecology of Bretschneidera sinensis (hemsley),a rare and endangered tree in China

Bretschneidera sinensis,a monotypic species mainly distributed in china,was listed in national key protected wild plants as a rare and tertiary relict tree. pollination ecology of b. sinensis was studied to reveal its floral morphology,breeding system and possible bottlenecks for its weak natural regeneration. results indicated that b. sinensis has an outcrossing-entomophily breeding system with protogyny and a high p/o ratio,and is pollinated by a variety of insects,with the main pollinators belonging to hymenoptera. it was the integrative factor that contributed to its low fruit production. the fragmentation of the habitat with increased inbreeding might be the most important factor for the diminution of this rare species. other factors in reproduction also cause the low fruit production,includes low numbers of flowering individuals,low pollen transfer efficacy,weak fruit retention and the short flowering season etc. meanwhile,bottlenecks in subsequent life history stages,such as low survivorship of seeds and lack of seedlings were also observed which indicated reduced fitness for its population development.