Science Division, Department of Environment and Conservation, Locked Bag 104, Bentley Delivery Centre, WA 6983, Australia, Margaret.Byrne@dec.wa.gov.au
Evolutionary history is an important component of understanding species responses to historical climatic change and its influence on current distributions. The Australian biota has been significantly influenced by Pleistocene climatic oscillations that ranged from warm wet conditions in interglacials to cool dry environments during glacial maxima, and that became more extreme from the mid Pleistocene with increasing aridity. Genetic signatures in plants reveal multiple levels of divergence and complex geographical structuring in both arid environments, where the effects of increased aridity may have been less significant, and in mesic environments where increased aridity would be expected to lead to major contraction of the biota. In many species these genetic signatures of high diversity and endemism indicate persistence of the biota through climatic oscillations over multiple glacial cycles as a major response to changing climatic conditions. In some species there are signatures of expansion in parts of the range and in others a signal of major refugia in buffered coastal areas and ranges. There is significant interest in understanding the role of historical refugia in facilitating persistence through the Pleistoicene, and their potential role in conservation of the current biota under future climate variability. Areas of refugia and regions facilitating localised persistence highlight the importance of dynamic evolutionary processes and a mosaic of habitats in heterogenous landscapes for species persistence though changing environmental conditions.