Dioecy in the Solanaceae is rare, occurring in less than 1% of species and documented for only two species from South America. We herein report the occurrence of functional, cryptic dioecy in the tropical, New World genus, Deprea. Study of herbarium material of the Venezuelan endemic, D. paneroi, revealed sex-related morphological distinctions that tentatively served to divide collections into male and female morphs. This discovery prompted investigation of population structure, crossing studies, and morphometric analyses among 95 individuals comprising the largest known population. About 60% of the population was reproductive, and of these about equal numbers exhibited female or male characteristics. Plants that bore fruit and possessed small, barren anthers were characterized as female. Plants that lacked fruit and produced pollen in significantly larger anthers were characterized as male. The morphology, receptivity, and phenology of development of pistils were identical in both forms. Because uninterrupted pollen tube growth was identical in all crosses and controls, relative differences in ovary size among experimental plants were used to deduce which ovaries were developing into fruit. Results of crossing studies revealed no significant differences in the development of ovaries between open pollinated female controls and female x male crosses. In contrast, ovaries among bagged female controls were significantly smaller than those of either open pollinated controls or crosses. The ovaries remained small in all male controls and male x male crosses. These results suggest that only female x male crosses produce fruit. In addition, seeds from a female plant produced healthy, flowering individuals indicating lack of post-fertilization reproductive barriers among female/male crosses. Dioecy in the family, and possible mechanisms for the evolution of dioecy in D. paneroi are discussed.

Key words: crossing studies, Deprea, dioecy