title: Biogeography and speciation of terrestrial fauna in the south-western Australian biodiversity hotspot.
abstract: 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 taxonomically documenting many of the more diverse invertebrate lineages. The latter remains central to any attempt to appreciate holistically biogeographic patterns and processes in SWWA, and molecular phylogenetic studies should - where possible - also lead to tangible taxonomic outcomes.
authors.affiliation: Australian Centre for Evolutionary Biology and Biodiversity, School of Earth and Environmental Sciences, The University of Adelaide, North Terrace, Adelaide, South Australia 5005, Australia.|Department of Terrestrial Zoology, Western Australian Museum, Locked Bag 49, Welshpool DC, Western Australia 6986, Australia.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Rix
authors.affiliation: Department of Ecology and Evolutionary Biology, Yale University, 21 Sachem Street, New Haven, CT 06520, U.S.A.
authors.forename: Danielle L
authors.initials: DL
authors.lastname: Edwards
authors.affiliation: Science Division, Department of Parks and Wildlife, Locked Bag 104, Bentley DC, Western Australia 6983, Australia.
authors.forename: Margaret
authors.initials: M
authors.lastname: Byrne
authors.affiliation: Department of Terrestrial Zoology, Western Australian Museum, Locked Bag 49, Welshpool DC, Western Australia 6986, Australia.|School of Animal Biology, Centre for Evolutionary Biology, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Harvey
authors.affiliation: Australian National Wildlife Collection, CSIRO National Facilities and Collections, GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia.
authors.forename: Leo
authors.initials: L
authors.lastname: Joseph
authors.affiliation: Department of Terrestrial Zoology, Western Australian Museum, Locked Bag 49, Welshpool DC, Western Australia 6986, Australia.|School of Animal Biology, Centre for Evolutionary Biology, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia.|Centre of Excellence in Natural Resource Management, University of Western Australia, PO Box 5771, Albany, Western Australia 6332, Australia.
authors.forename: J Dale
authors.initials: JD
authors.lastname: Roberts
mesh_terms: D000818:Animals; D001315:Australia; D044822:Biodiversity; D049810:Genetic Speciation; D010802:Phylogeny; D058974:Phylogeography
keywords: Arachnida; Chordata; Decapoda; Diplopoda; Insecta; Mollusca; Onychophora; conservation; evolution; systematics