Circumscriptions of the genus Hibiscus and the tribe Hibisceae (Malvaceae) are based on morphological features that are not unique in the family. An examination of the literature regarding putatively ancestral morphological features revealed that Hibiscus and Hibisceae may be defined by shared ancestral features, and thus are unlikely to be monophyletic groups. These phylogenetic hypotheses were tested using two chloroplast DNA sequences (a coding region—ndhF, and a non-coding region—the rpl16 intron). Several genera usually placed in Hibisceae were found to occupy positions sister to the rest of the family, as was predicted from our reevaluation of their morphological features. Although the earliest divergences in the family were not resolved by chloroplast DNA topologies alone, several morphological features, when analysed in combination with ndhF, suggested a possible resolution of the basal polytomy. These early divergences are represented by extant genera with relatively restricted distributions, which all possess Australasian species that are sister to more widespread and diverse lineages. This suggests the novel hypothesis that eastern Gondwana may be the centre of origin of the family. The pollen fossil record is consistent with this possibility, but does not support it unambiguously. Unexpectedly the tribes Decaschistieae and Malvavisceae as well as other genera of Hibisceae nest within Hibiscus. Nomenclatural upheavals concerning Hibiscus, one of the world's most popular horticultural plant genera, will be difficult to avoid.

Communicating Editor: James F. Smith