Reproductive biology of Cipocereus minensis (Cactaceae)-A columnar cactus endemic to rupestrian fields of a Neotropical savannah

We studied the reproductive biology of Cipocereus minensis, an endemic columnar cactus of the Espinhaço Mountain Range, Southeastern Brazil, focusing on floral biology, breeding system, and pollination. We described floral morphology and evaluated the role of nocturnal and diurnal pollinators on the reproductive success in two populations. C. minensis has large, horizontal, cream-colored, chiropterophilous flowers with rigid petals that open at dusk and close on the following morning. Flowers produced a huge amount of pollen grains and nectar production was nocturnal. Controlled pollination experiments revealed that the cactus is an obligate xenogamous species. Visitor-exclusion experiments revealed that the nocturnal visitors (bats) are the prominent pollinators whereas hummingbirds and social bees, which visited the flowers early in the morning, contributed little to fruit set. We conclude that the reproductive success of this endemic columnar cactus is threatened in the absence of the effective pollinating bats.