Lines in the land: A review of evidence for eastern Australia's major biogeographical barriers to closed forest taxa

摘要

The influence of climatic changes occurring since the late Miocene on Australia’s eastern mesic ecosystems has\udreceived significant attention over the past 20 years. In particular, the impact of the dramatic shift from\udwidespread rainforest habitat to a much drier landscape in which closed forest refugia were dissected by open\udwoodland/savannah ecosystems has long been a focal point in Australian ecology and biogeography. Several\udspecific regions along the eastern coast have been identified previously as potentially representing major\udbiogeographical disjunctions for closed forest taxa. Initially, evidence stemmed from recognition of common zones\udwhere avian species/subspecies distributions and/or floral communities were consistently separated, but the body\udof work has since grown significantly with the rise of molecular phylogeographic tools and there is now a\udsignificant literature base that discusses the drivers, processes and effects of these hypothesised major\udbiogeographical junctions (termed barriers). Here, we review the literature concerning eight major barriers\udargued to have influenced closed forest taxa; namely, the Laura Basin, Black Mountain Corridor, Burdekin Gap,\udSaint Lawrence Gap, Brisbane Valley Barrier, Hunter Valley Barrier, Southern Transition Zone and East\udGippsland Barrier. We synthesise reported phylogeographical patterns and the inferred timing of influence with\udcurrent climatic, vegetation and geological characteristics for each barrier to provide insights into regional\udevolution and seek to elicit common trends. All eight putative biogeographical barriers are characterised\udcurrently by lowland zones of drier, warmer, more open woodland and savannah habitat, with adjacent closed\udforest habitats isolated to upland cool, wet refugia. Molecular divergence estimates suggest two pulses of\uddivergence, one in the early Miocene (~20–15 Mya) and a later one from the Pliocene–Pleistocene (~6–0.04 Mya).\udWe conclude with a prospectus for future research on the eastern Australian closed forests and highlight critical\udissues for ongoing studies of biogeographical barriers worldwide.