Phylogeny and biogeography of the African genus Virectaria Bremek. (Sabiceeae s.l., Ixoroideae, Rubiaceae)

摘要

The phylogenetic relationships of the tropical African genus Virectaria with its associated genera within the tribe Sabiceeae s.l. (Ixoroideae and Rubiaceae) were inferred from the combined analysis of nuclear ITS and chloroplast rpoC1 and trnT-F nucleotide sequence data. Phylogenetic relationships within Virectaria were investigated using combined analyses of ETS (nrDNA), ITS, rpoC1 and trnT-F sequence data. The present analyses further show that Hekistocarpa is sister to the Tamridaea-Virectaria-Sabicea clade, Tamridaea and Virectaria are sister genera, and Sabicea s.l. is sister to the Tamridaea-Virectaria clade. Our results strongly support the monophyly of Virectaria and the sister-group relationships between V. multiflora and V. herbacoursi, V. angustifolia and V. procumbens, and V. major and V. belingana. Our analyses indicate a tropical African origin for Sabiceeae s.l., a long isolated evolution for Tamridaea and a wide range of dispersal of Virectaria species in the Lower-Guinean, Upper-Guinean and Congolian regions, without a clearly defined direction of migration.