Raimúndez-Urrutia, E. (Departamento de Biología de Organismos, División de Ciencias Biológicas, Universidad Simón Bolívar, Caracas, Venezuela) and C. Varela (Postgrado en Ciencias Biológicas, Universidad Simón Bolívar, Caracas, Venezuela). Predispersal reproductive ecology of Gronovia scandens L. (Loasaceae), a plant from disturbed habitats. J. Torrey Bot. Soc. 132: 581–589. 2005.—Gronovia scandens is a short-lived climbing herb that lives in disturbed sites and has become a weed in crop lands as a result of its rapid vegetative expansion and population growth, although it can also develop in late succesional stages. Study of its predispersal reproductive ecology showed that this plant is a self-compatible outcrossing annual with delayed autogamy; i.e., it exhibits a mixed mating system in which outcrossing has a temporal advantage over selfing. The outcrossing advantage is revealed by the high biomass allocation to male structures and pollinator attractants in the flower and the high pollen/ovule ratio. The delayed autogamy is mainly due to the fact that the anthers adhere to the stigma at the end of anthesis allowing seed production when outcrossing fails. The hymenopterans that were captured and identified as pollinators made non-specialized foraging movements and loaded scarce pollen on their bodies, although the body areas with pollen made contact with the stigma. Nevertheless, the presence of a single ovule per flower, delayed autogamy and a relatively low fruit cost related with the flower cost, favor a high efficiency in fruit (seed) production.