Reproductive biology of Cipocereus minensis (Cactaceae) ? a columnarcactus endemic to rupestrian fields of a Neotropical savannah.

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