Paraphyly and Polyphyly in the Worldwide Tribe Rubieae (Rubiaceae): Challenges for Generic Delimitation1,2

Abstract On the basis of multidisciplinary studies on the tribe Rubieae, we contribute to the current discussion on paraphyly and supraspecific taxa that do not contain all descendant species of an ancestral clade. Rubieae belong to the large, predominantly tropical and woody family Rubiaceae and include possibly ≤ 1000 mostly temperate and herbaceous species with worldwide distribution. Our studies span distinctive groups throughout the tribe, consist of a maximum parsimony analysis of plastid atpB-rbcL and rpL32-trnL DNA sequences, and are summarized in a condensed strict consensus tree. A corresponding two-dimensional scheme illustrates alternative hypotheses for phylogenetic relationships among all major Rubieae clades identified. The small relictual genus Kelloggia Torr. in Benth. & Hook. f., formerly excluded from the Rubieae, is supported as a remnant of the ancestors of the tribe. Didymaea Hook. f. and Rubia L. represent early phylogenetic side lines. All other Rubieae form a large monophyletic cr...