ABSTRACT
Australia’ s biota has long fascinated scientists and nonscientists alike for its uniqueness and taxon richness (Keast, 1981; Cranston and Naumann, 1991; Crisp et al., 1999; Yeates et al., 2003; Austin et al., 2004; Chapman, 2009; Cranston, 2010). In reference to these biodiversity values, much has been made of Australia’ s separation and isolation, and its high endemism is diagnostic for the continent (Crisp et al., 1999). This is in large part an outcome of intracontinental drivers during the Late Palaeogene (Byrne et al., 2008, 2011; Rix et al., 2015), which implicitly characterise Australia as a biogeographic unit in itself, with many lineage radiations attributed to the aridication of Australia (Clayton, 1984; Schodde, 1989; Greenwood and Christophel, 2005). As a consequence, Australia is stamped with arid and semiarid biogeographic regions, particularly the southwest corner of Western Australia (Hopper, 1979; Rix et al., 2015; Cassis and Symonds, 2016) and the interior deserts (Cracraft, 1991; Crisp et al., 1995; Byrne et al., 2011), as well as mesic refugia (e.g. the Wet Tropics; Williams and Pearson, 1997; Boyer et al., 2016). The counterpoint to this is that Australia is a biogeographic composite (Giribet and Edgecombe, 2006), particularly for supraspecic taxa, with multiple and in most cases older histories, including a replicated east Gondwanan signature, which couples Australia’ s biota with New Zealand (Stow et al., 2015), the rises (Lord Howe and Norfolk Island), Melanesia (New Guinea, New Caledonia, the southwest Pacic archipelagos) (Burbidge, 1960), and cool, temperate South America (Brundin, 1966; Swenson et al., 2001). In contrast, other components of Australia’ s biota have a palaeotropical signature (Herbert, 1932; Webb and Tracey, 1981), with some taxon-area relationships explained by an Indo-Pacic model, which connects monsoonal Australia to West Africa through the Indian subcontinent (Schuh and Stonedahl, 1986), or with more restricted area relationships, such as mammal taxa east of Lydekker’ s Line (Simpson, 1977). More recently, there has been characterisation of the Australian Monsoon Tropics, highlighting its biogeographic complexity, intermixing palaeotropical and Gondwanan elements as well as local endemics (Bowman et al., 2010).
