Introduction
Oreocereus celsianus is a columnar cactus of the high Andes of Bolivia, Peru, and northern Argentina. Researchers set out to identify its primary pollinator—was it a bat (as in many columnar cacti), or something else?
The Details
O. celsianus can reach about 20 ft tall. Its high, tubular, pinkish flowers and rich nectar suggest bird pollination. Flowers open in the afternoon of the first day and continue into the next, when diurnal visitors can access abundant nectar.
Butterflies, flies, bees, and moths visited the flowers, but bats were not observed. Hummingbirds were the key visitors. Three species appeared regularly—the Giant Hummingbird (Patagona gigas), the Wedge-tailed Hillstar (Oreotrochilus adela), and the Sparkling Violetear (Colibri coruscans)—with the Giant Hummingbird by far the most frequent and effective.
Fruit set was high under natural conditions. The species is self-compatible and can set fruit via both self- and cross-pollination—a “fail-safe” mixed mating system that helps ensure reproduction when pollinators are scarce. In the subtropical Andes, flowering typically occurs in summer (roughly December–March), with fruits ripening in about six weeks.
Additional Reading: Pollination Biology of Oreocereus celsianus
