Nurse Plant and Floral Biology of a Rare Night‐Blooming Cereus, Peniocereus striatus (Brandegee) F. Buxbaum

The Sonoran night‐blooming cereus (Peniocereus striatus) is a rare cactus found in the Sonoran Desert. Its survival is dependent on maintenance of its habitat and its ability to recruit. This study evaluates the role of nurse plants in P. striatus survival and the floral and pollination ecology controlling recruitment. A strong association was detected between P. striatus and its nurse plants, which include Olneya tesota and Larrea tridentata. Because of the harvesting of Olneya tesota and Prosopis velutina for charcoal over a 20,000 square km area of its range, this night‐blooming cereus is vulnerable to rapid habitat degradation in both Sonora (Mexico) and adjacent Arizona (U.S.A.). The temporal and local scarcity of sphingid moths available for pollination caused by pesticides and small flower numbers, appear to produce low recruitment rates. These two important threats to the biotic associates of this cactus have increased its natural rarity. This can only be alleviated through international cooperation.