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We confirmed functional dioecy of Withania aristata via field and greenhouse studies. Male flowers are significantly larger. Female flowers bear stamens with no pollen; males bear 220 000 grains. Stigmata of male flowers senesce in buds. Anatomical observations confirm more ovules in females and an ovarian nectary in both sexes. We detected nectar in female flowers in thegreenhouse but found no nectar in males. Thus, males offer pollen and females nectar. Females bear large numbers of fruits and, infrequently, male plants bear few significantly smaller fruits with few seeds. Outcrosses of females (self crosses impossible without pollen) yielded fruits in young buds, older buds, and open flowers. Self crosses of male flowers succeeded only with veryyoung buds. Although functionally dioecious, this species manifests self-compatibility; however, no fruits are produced autonomously. Bee species (Lassioglossum, Amegilla, Apis) visit flowers and mature buds. Bud visits in which bees force petal tips apart, coupled with self-compatibility, may explain infrequent fruit on males. Thus, dioecy in W. aristata seems to have evolved from self-compatible ancestors, that leaky dioecy may have been favored during colonization, and, that despite autogamy and a low floral visition rate, this endemic enjoys a high rate of reproductive success. Fil: Anderson, Gregory. University Of Connecticut; Estados Unidos Fil: Bernardello, Gabriel Luis Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Opel, Matthew R.. University Of Connecticut; Estados Unidos Fil: Santos-Guerra, Arnoldo. Jardín de Aclimatación de La Orotava; España Fil: Anderson, Mona. University Of Connecticut; Estados Unidos |
