Patterns of Distribution of Acacia in Australia

Abstract

Patterns of distribution are described for the three subgenera and nine sections that make up the Australian Acacia flora. Subgenus Phyllodineae (833 species) is widespread and contains 99% of the species; subgenus Acacia (six species) and subgenus Aculeiferum (one species) are poorly represented and virtually confined to the north of the continent. The geographic patterns of species-richness are strongly influenced by sections Phyllodineae (352 species), Juliflorae (219 species) and Plurinerves (178 species). Section Phyllodineae has centres of richness south of the Tropic of Capricorn in temperate and adjacent semiarid areas of eastern, south-eastern and south-western Australia. The section is poorly represented in the tropics. The closely related sections Juliflorae and Plurinerves predominate in the north of the continent, semiarid areas of the south-west, many rocky tablelands of the Arid Zone and along the Great Dividing Range and adjacent inland riverine lowland areas in eastern Australia. The remaining four sections contribute little to the overall patterns of species-richness. The principal speciespoor areas are sandy and fluvial lowland regions of the Arid Zone. In eastern Australia, sections Botrycephalae, Juliflorae, Phyllodineae and Plurinerves show discontinuous patterns of species-richness along the Great Dividing Range. All sections have species whose ranges terminate in the area of the McPherson-Macleay Overlap region.