Evolutionary History

Abstract

Australia is a vast continent with a range of environments broadly differentiated into three major biomes. The best studied of these, the mesic biome, is confined to the eastern coast and the southeast and southwest corners and has pockets of ever-wet rainforest along the east coast. The monsoon tropics biome occurs in the northern part of the continent including Cape York Peninsula in the east, and the arid-zone biome covers the vast central and western parts of the continent, generally west of the Great Dividing Range. The arid zone is Australia’s largest biome, occupying approximately 70% of the entire continent (Fig. 1a) and broadly corresponding to the Eremaean and northern desert regions of the Australian Bioregionalisation Atlas (Ebach et al. 2015) (Fig. 1b). It covers a range of environments such as sandy deserts, gibber deserts and steppes, ranges and coastal plains and hosts a variety of vegetation types, shrub woodlands, acacia and mallee eucalypt shrublands, spinifex grasslands, tussock and hummock grasslands and chenopod shrublands. On average, the arid zone is only 300 m above sea level with low relief and a broad flat plain covering most of the central western area (Williams 1984; Pain et al. 2012; Pillans 2018).