NURSE PLANT AND FLORAL BIOLOGY OF A RARE NIGHT-BLOOMING CEREUS, PENIOCEREUS-STRIATUS (BRANDEGEE) BUXBAUM,F.

The Sonoran night-blooming cereus (Peniocereus striatus) is a rare cac tus found in the Sonoran Desert. Its survival is dependent on maintena nce of its habitat and its ability to recruit. This study evaluates th e role of nurse plants in P. striatus survival and the floral and poll ination ecology controlling recruitment. A strong association was dete cted between P. striatus and its nurse plants, which include Olneya te sota and Larrea tridentata. Because of the harvesting of Olneya tesota and Prosopis velutina for charcoal over a 20,000 square km area of it s range, this night-blooming cereus is vulnerable to rapid habitat deg radation in both Sonora (Mexico) and adjacent Arizona (U.S.A). The tem poral and local scarcity of sphingid moths available for pollination c aused by pesticides and small flower numbers, appear to produce low re cruitment rates. These two important threats to the biotic associates of this cactus have increased its natural rarity. This can only be all eviated through international cooperation