Biogeography of the Kimberley, Western Australia: a review of landscape evolution and biotic response in an ancient refugium

Aim We review the biogeography of the Kimberley, with a particular focus on the geological and landscape history of the region. We identified broad geological and biogeographical discontinuities across the Kimberley, and propose a number of testable hypotheses concerning how the evolution of these land-forms may have harboured and structured genetic diversity across the region. Location The Kimberley region, north-western Australia. Methods The literature available on the Kimberley is summarized, in particular regarding the evolution of Kimberley landscapes and climate. Previous genetic work was assessed in order to establish whether common patterns exist, and to identify concordance with four putative broad-scale biogeographical breaks to be tested when appropriate fine-scale genetic data become available: (1) the geological division between the Kimberley Plateau and surrounding deformation zones of the King Leopold and Halls Creek orogens; (2) the east-west geological divide between different sandstone units of the Kimberley Plateau; (3) major drainage divisions and river courses; and (4) the previously defined bioregions and subregions of the Interim Biogeographical Regionalisation for Australia (IBRA), the Northern and Central Kimberley. Results Genetic patterns across a number of taxonomic groups in the Kimberley lend support to the four biogeographical scenarios we outline, and these now need to be tested with additional data. Main conclusions The biogeographical patterns emerging from studies of Kimberley biota are characterized by high endemism and deep divergences. In addition, a complex relationship between the Kimberley and other monsoon tropical bioregions and the adjacent deserts suggests multiple expansions into the arid zone, and vicariance and isolation in upland refugia within the topographically complex region. Fine-scale genetic data are beginning to be accumulated for Kimberley taxa, and concordant phylogeographical patterns across disparate groups suggest that regional differences in geological structure and land-forms may have played an important role in shaping the distribution and evolutionary patterns of extant biota. Future palaeoecological, geomorphological and finer scale phylogenetic investigations based on increased sampling and emerging genetic technologies will shed more light on the evolution of the Kimberley biome amidst one of the greatest environmental changes in the Cenozoic: the widespread aridification of the Australian continent.