The woody and fleshy-fruited genera Anthocleista, Fagraea, and Potalia (Gentianaceae) are tree- or shrub-like tropical gentians previously associated with Loganiaceae. Molecular data from rbcL, matK, and the trnL intron (along with morphological and phytochemical evidence) has shown that this group is deeply nested inside Gentianaceae. Specific relationships of the group are to lineages of herbaceous and dry-fruited genera that are more basally placed, implying secondary derivations of tree-like habit and fleshy fruits in the family. Anthocleista and Potalia also diverge from the usual gentian floral bauplan in having supermerous corollas and staminal parts (being 8-16-merous). SEM studies have revealed multiplication of corolline and staminal primordia based on an initially 4-merous primordia area. Anthocleista, Fagraea, and Potalia also appear to lack postgenital fusion of carpels, which is typical for other gentians. The congenitally fused carpels in these genera may have predisposed evolution of their fleshy, indehiscent fruits. Preliminary results from nuclear ITS (internal transcribed spacer) sequences show the three genera to be monophyletic, with African-Malagasy Anthocleista sister to American Potalia, and with Asian-Australian-Pacific Fagraea as the sister to this pair. This is in contradiction to an earlier morphology-based cladistic study, which showed a paraphyletic Fagraea. Morphology-based species level results in Potalia show white-sand, narrowly endemic species from central Amazonia to be most basally placed, and species from Central America, Guianas, and non-white-sand Amazonian areas in more derived positions. This supports the hypothesis that lowland white-sand areas in the Neotropics may be relictual areas that harbor many ancestral and phylogenetically divergent plant lineages.

Key words: biogeography, floral development, Gentianaceae, molecular systematics, phylogeny, Potalieae