Symbolanthus (Gentianaceae, Helieae) is a genus of small trees, shrubs and herbs distributed in South America (the central and northern Andes and the Guayana Highlands), and southern Central America. To discover the pattern of Symbolanthus evolution and biogeography in South America, we performed cladistic analyses on selected species of Symbolanthus and the closely related Wurdackanthus of the Guayana Highlands and the Lesser Antilles. Morphological and molecular data (5S-NTS rDNA sequences) were gathered from individual plant samples, mainly from herbarium specimens. 5S-NTS sequences did not resolve internal relationships well in Symbolanthus, and show that the genus may be a recently and rapidly diverging clade. Analyzing 30 morphological characters and combinations of morphology and 5S-NTS sequences gave us better-resolved trees, but with weak support for internal clades. These data confirm that Wurdackanthus is paraphyletic and that the basalmost species of the Wurdackanthus-Symbolanthus clade is W. frigidus, of the Lesser Antilles. This species is noticeably distinct, molecularly and morphologically, from the rest of the clade. Furthermore, W. argyreus, of the Guayana Highlands, is probably the next most basal species in the clade. While neither of the Wurdackanthus species has a floral corona like Symbolanthus, W. frigidus has staminal "pockets" or gaps between the corolla and the base of the adnate filaments. These gaps are also found in other Helieae taxa and may have been an evolutionary precursor of the corona in Symbolanthus. Finally, there are at least two and possibly three separate lineages of Guayana Highland (tepui) taxa, with nearest relatives in the Andes and/or Central America. Our results show a biogeographic pattern in which migration between tepuis and the Andes and Central America played a strong role in the evolution of Symbolanthus.

Key words: 5S-NTS, biogeography, Gentianaceae, Guayana Highlands, Symbolanthus, Wurdackanthus