The south-western land division of Western Australia (SWWA), bordering the temperate Southern and Indian Oceans, is the only global biodiversity hotspot recognised in Australia. Renowned for its extraordinary diversity of endemic plants, and for some of the largest and most botanically significant temperate heathlands and woodlands on Earth, SWWA has long fascinated biogeographers. Its flat, highly weathered topography and the apparent absence of major geographic factors usually implicated in biotic diversification have challenged attempts to explain patterns of biogeography and mechanisms of speciation in the region. Botanical studies have always been central to understanding the biodiversity values of SWWA, although surprisingly few quantitative botanical analyses have allowed for an understanding of historical biogeographic processes in both space and time. Faunistic studies, by contrast, have played little or no role in defining hotspot concepts, despite several decades of accumulating quantitative research on the phylogeny and phylogeography of multiple lineages. In this review we critically analyse datasets with explicit supporting phylogenetic data and estimates of the time since divergence for all available elements of the terrestrial fauna, and compare these datasets to those available for plants. In situ speciation has played more of a role in shaping the south-western Australian fauna than has long been supposed, and has occurred in numerous endemic lineages of freshwater fish, frogs, reptiles, snails and less-vagile arthropods. By contrast, relatively low levels of endemism are found in birds, mammals and highly dispersive insects, and in situ speciation has played a negligible role in generating local endemism in birds and mammals. Quantitative studies provide evidence for at least four mechanisms driving patterns of endemism in south-western Australian animals, including: (i) relictualism of ancient Gondwanan or Pangaean taxa in the High Rainfall Province; (ii) vicariant isolation of lineages west of the Nullarbor divide; (iii) in situ speciation; and (iv) recent population subdivision. From dated quantitative studies we derive four testable models of historical biogeography for animal taxa in SWWA, each explicit in providing a spatial, temporal and topological perspective on patterns of speciation or divergence. For each model we also propose candidate lineages that may be worthy of further study, given what we know of their taxonomy, distributions or relationships. These models formalise four of the strongest patterns seen in many animal taxa from SWWA, although other models are clearly required to explain particular, idiosyncratic patterns. Generating numerous new datasets for suites of co-occurring lineages in SWWA will help refine our understanding of the historical biogeography of the region, highlight gaps in our knowledge, and allow us to derive general postulates from quantitative (rather than qualitative) results. For animals, this process has now begun in earnest, as has the process of ta...
Abstract.A major challenge confronting many contemporary systematists is how to integrate standard taxonomic research with conservation outcomes. With a biodiversity crisis looming and ongoing impediments to taxonomy, how can systematic research continue to document species and infer the 'Tree of Life', and still maintain its significance to conservation science and to protecting the very species it strives to understand? Here we advocate a systematic research program dedicated to documenting short-range endemic taxa, which are species with naturally small distributions and, by their very nature, most likely to be threatened by habitat loss, habitat degradation and climate change. This research can dovetail with the needs of industry and government to obtain high-quality data to inform the assessment of impacts of major development projects that affect landscapes and their biological heritage. We highlight how these projects are assessed using criteria mandated by Western Australian legislation and informed by guidance statements issued by the Environmental Protection Authority (Western Australia). To illustrate slightly different biological scenarios, we also provide three case studies from the Pilbara region of Western Australia, which include examples demonstrating a rapid rise in the collection and documentation of diverse and previously unknown subterranean and surface faunas, as well as how biological surveys can clarify the status of species thought to be rare or potentially threatened. We argue that 'whole of biota' surveys (that include all invertebrates) are rarely fundable and are logistically impossible, and that concentrated research on some of the most vulnerable elements in the landscape -short-range endemics, including troglofauna and stygofauna -can help to enhance conservation and research outcomes.
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