Format: ORAL

Anze Zerdoner Calasan1 2, Kelly A. Shepherd2, Karol Krak3, Bohumil Mandk3, Gudrun Kadereit1

1 Systematics, Biodiversity and Evolution of Plants, Faculty of Biology, Ludwig Maximilian University of Munich, Germany 2 Western Australian Herbarium (PERTH), Biodiversity and Conservation Science, WA, Australia 3 Plant Biodiversity and Evolution, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Czech Republic

The vast arid region covering about 70% of Australian continent remains one of the worlds largest and least explored territories. Despite its extremely adverse environmental conditions, this area is rich in xerophytic plant life that has adapted to challenging physiological and ecological constraints. Despite such a high diversity, this flora is thought to have evolved along a similar evolutionary trajectory, known as the littoral connection hypothesis. This hypothesis states that the most recent common ancestors of contemporary arid floral elements arrived in Australia already preadapted to increased aridification and/or salinisation, and were thus able to thrive in environmental conditions that have otherwise driven most mesic floral elements to extinction. AlongsideAsteraceae, Fabaceae, and Myrtaceae, Amaranthaceae are one of the species-richest plant families in this arid zone that underwent rapid diversification events. In our studies, we employed various RADseq and HybSeq techniques to resolve the phylogenies of numerous recalcitrant groups of xerophytic Australian Amaranthaceae and compare their evolutionary histories. Our analyses focused on understanding the spatiotemporal patterns in these lineages and the underlying biological mechanisms that drove their rapid diversification and survival. Despite their separate arrivals in Australia during the Miocene/Pliocene transition, our analyses unveiled shared spatiotemporal patterns among these groups, lending support to the littoral connection hypothesis. Some lineages exhibited floral exchanges between Australia and South Africa, while polyploidisation, potentially driving speciaton, appeared to be restricted to certain taxa. Future research aims to expand these investigations to other arid-adapted elements in the Australian outback with the main aim to further validate the littoral connection hypothesis and understand the broader role of polyploidisation in the evolution of Australian arid clades beyond Amaranthaceae. Our research sheds light on the evolutionary adaptations of plants in some of Earths harshest environments, providing valuable insights into the mechanisms driving biodiversity in arid regions.