Molecular phylogeny of the tribe Anthospermeae (Rubiaceae): Systematic and biogeographic implications

Phylogeny of the tribe Anthospermeae is estimated on the basis of nucleotide sequence variation in the ITS region (nuclear ribosomal DNA) and the rps16 intron (plastid DNA). It is concluded that it is dubious whether the tribe is monophyletic including Carpacoce. If Carpacoce does belong to the tribe, then it is the sister group of all other genera. There is no support for the traditional subdivision of the tribe into three subtribes. Anthospermum, Galopina, Nenax and Phyllis form one strongly supported subclade. Coprosma, Durringtonia, Leptostigma, Nertera, Normandia, Opercularia and Pomax form another subclade in all most parsimonious trees, but this subclade lacks jackknife support. Opercularia and Pomax, referred to the subtribe Operculariinae, form a basal grade of this second group. However, trees on which Operculariinae are monophyletic are only one step longer than the most parsimonious ones. Normandia is deeply nested within Coprosma. The subdivision of Coprosma into two subgenera is shown to be artificial. It is suggested that the ancestral area of Anthospermeae is Africa, and that the group was spread by long-distance dispersal to north-eastern Antarctica. It is further suggested that occurrences in Hawaii, Tristan da Cunha, and America are due to long-distance dispersal at a time much later than primary cladogenesis.