Phylogenetic relationships among species of the neotropical genus Randia (Rubiaceae, Gardenieae) inferred from molecular and morphological data

Relationships among 38 taxa of Randia (Rubiaceae, Gardenieae) are estimated using nuclear ribosomal internal transcribed spacers (ITS), the 5S non-transcribed spacer (5S-NTS), and six morphological characters. In addition to Randia, 13 species from eight related genera in Gardenieae (four African, four neotropical) formed the ingroup. Three species from three more distantly related genera in Gardenieae (one African, two neotropical) were chosen as the outgroup. Representatives of the African ingroup genera Calochone, Macrosphyra, Oligocodon and Preussiodora formed a well supported monophyletic group as did the neotropical genera Rosenbergiodendron, Sphinctanthus and Tocoyena. Only when including morphological characters did Randia form a monophyletic group corresponding approximately to contemporary circumscription of the genus, but in this analysis Casasia appears sister to a group of Mexican, Central American, and Antillean Randia. There is no strong jackknife support, however, for either Randia or Casasia to be monophyletic. It is concluded that Randia is comprised of several distinct groups, each with its own geographical distribution. One group of Mexican, Central American, and Antillean Randia, including the type species, can be recognized as Randia in a strict sense. Two other South American groups can be recognized as separate taxa. One of these groups comprises mainly lowland species, and the second is comprised of strictly Andean species.