A phylogeny and study of floral traits in the neotropical genus Gasteranthus (Gesneriaceae)

Abstract

The genus Gasteranthus (Gesneriaceae), with 41 currently described species, including 3 subspecies, occurs in Central and South America. This genus has a center of diversity in Ecuador and is comprised of herbs or subshrubs that grow predominately in humid to wet tropical forests and is especially abundant near streams and waterfalls. Species of Gasteranthus have two morphologically different corolla shapes. The hypocyrtoid (pouched) shape is defined by an inflated ventral pouch and constricted throat while the campanulate (non-pouched) shape is defined by a funnelform corolla. Molecular sequence data generated from nrDNA (ITS and ETS) and cpDNA (matKR and trnL-F) were generated for 57 taxa representing 32 species of Gasteranthus and 25 species from closely related genera. This study strongly supports that shifts between campanulate and hypocyrtoid flowers have occurred several times within Gasteranthus, though the result is equivocal as to which floral form is plesiomorphic. Phylogenetic analyses support that Gasteranthus dressleri should be transferred to Cremosperma and given a new combination. Phylogenetic results and fieldwork have shown that new circumscriptions are necessary for names previously synonymized in Gasteranthus pansamalanus and Gasteranthus lateralis. Finally, Gasteranthus aurantiacus is recognized as a synonym of Gasteranthus mutabilis.