Format: ORAL

Luiz A. Cauz-Santos1*, Rosabelle Samuel1, Dominik Metschina1, Maarten J.M. Christenhusz2,3, Ovidiu Paun1and Mark W. Chase1,2,3

1 Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A- 1030 Vienna, Austria 2 Royal Botanic Gardens, Kew, Richmond TW9 3DS, UK 3 Department of Environment and Agriculture, Curtin University, Perth, Western Australia, Australia

For the last six million years, the Australian Eremaean Zone (EZ) has been as dry as today. The flora and fauna of arid regions worldwide, including the EZ, have been hypothesised to have diversified widely before aridification began, in this case 20 Mya, and slowly adapted as aridity developed. Undocumented are more recently arrived plants that developed arid specialisations in situ. Here, we investigate the biogeography and timing of nativeallotetraploid tobaccos, Nicotiana sect. Suaveolentes, which putatively entered the EZ 5 Mya.The original allotetraploid migrants from South America were adapted to mesic areas ofAustralia and only recently radiated in the EZ after developing drought adaptations. Based oncoalescent and maximum likelihood analyses designed to corroborate timing of theAustralian radiation independently, arrival of Nicotiana sect. Suaveolentes occurredapproximately 6 Mya, followed by spread via multiple invasions across the EZ from theecologically highly diverse Pilbara District (Western Australia), which served as a mesicrefugium and cradle for adaptations to harsher conditions. These results demonstrate thatpoorly adapted plant groups can develop novel adaptations that permit them to disperseextensively and rapidly despite the extremes of heat and drought in the EZ.