Gasteranthus (Gesneriaceae; Beslerieae) includes 38 species restricted to the New World tropics. The genus has a limited distribution in Central and South America, with a center of diversity in western Ecuador. This study investigates cladistic relationships among species of Gasteranthus using floral and vegetative morphological data. Corolla shape in Gasteranthus ranges from funnelform to urceolate and ventricose, with additional variation in corolla spur and corolla ventral pouch morphology. Our analysis revealed that there were likely single primary innovations of the three major corolla types, although only one of the three types forms a monophyletic group. Apparently, ventricose corollas were derived from funnelform corollas and urceolate corollas were derived from ventricose corollas, making the funnelform and ventricose corolla groups both paraphyletic. Spurs have been lost twice in Gasteranthus. Conspicuousness of stomatal clusters is quite homoplastic given the phylogenetic hypothesis.

Communicating Editor: Thomas G. Lammers