Morfología y anatomía floral de la tribu Hamelieae (Rubiaceae)

We studied floral morphology and anatomy of seven genera of the tribe Hamelieae sensu Manns & Bremer with the goal to evaluate the potential of these characters in the circumscription of the tribe. Twenty two species of Hamelieae were studied as well as ten representative species of the Cinchonoideae, Ixoroideae, and Rubioideae subfamilies for comparative purposes. The Hamelieae members had stamens adnate to the corolla base, anther dorsifixed with introrse dehiscence, amphivasal vascular bundle in the filament, endothecium of one layer of cells, papillose stigma, axile placentation, orthotropous and unitegmic ovules, epidermal cells of the integument with tannins, and idioblasts with raphides in all whorls. Exostema and Hintonia (Cinchonoideae) share with Hamelieae the stamens adnate to the corolla base and the imbricate aestivation. However, these genera are unlike of the tribe because they have anthers with latrorse dehiscence, round filaments, ovoid styles with a constriction, anatropous ovules with basipetal orientation, and idioblasts with druses or crystal sands. Rubioideae and Cinchonoideae representatives unlike Hamelieae and species of Cinchonoideae studied have valvate and contorted to the left aestivation, anthers dorsifixed at the middle, stamens adnate to the throat of the corolla, and trichomes in the throat of the corolla tube. The imbricate aestivation, the occurrence of raphides, and the adnate stamens of the corolla base supported the relationships among Hamelieae and Cinchonoideae as suggested by molecular phylogenies.