SELENICEREUS-WITTII (CACTACEAE) - AN EPIPHYTE ADAPTED TO AMAZONIAN IGAPO INUNDATION FORESTS

The biology, ecology, and distribution of Selenicereus (Strophocactus) wittii, one of the least known taxa of Cactaceae, are described. This epiphyte climbs appressed to tree trunks with leaf-like, flattened st ems and is found exclusively along the high waterline of black water r ivers (Rio Negro, Vaupes, Apaporis) in the Igapo inundation forests of Amazonia. Ecophysiologically, S. wittli is a crassulacean acid metabo lism (CAM) plant. It bears white, nocturnal flowers 25 cm in length wh ich emit a fragrance consisting mainly of benzylalcohol, benzyl benzoa te, and benzyl salicylate. They exhibit an extreme sphingophilous synd rome as an adaptation to pollination by probably only two species of h awkmoth from the genera Amphimoena and Cocytius. The seeds, aberrant f or the family, contain air-filled chambers and are water-dispersed. Th us, S. wittii represents the paradoxical life form of an hydrochorous epiphytic cactus which withstands periodical inundation.