Format: ORAL

Elizabeth M. Joyce1

1 Systematics, Biodiversity and Evolution of Plants, Ludwig Maximilian University of Munich, Munich, Germany

The convergence of the Sunda continental shelf (Malaysia, parts of Indonesia and the Philippines) and the Sahul continental shelf (Australia and New Guinea) from c. 25 Mya was a significant event in global biogeography that resulted in the exchange of previously isolated floras (the Sunda-Sahul Floristic Exchange; SSFE). Despite the importance of the SSFE in shaping the flora of the region, much remains to be understood about the processes and patterns underlying it. To address this, we used Angiosperms353 target capture data to generate the most densely sampled phylogenetic tree of angiosperm order Sapindales to date, with 448 samples and c. 85% of the genera represented. Our tree resolves the relationships between Meliaceae, Simaroubaceae and Rutaceae and indicates that Nitrariaceae, Biebersteiniaceae and Sapindaceae emerged early in Sapindales, but the order of divergence remains unclear. Bayesian dating with 29 rigorously assessed fossil calibrations indicates that most Sapindalean families arose in the Cretaceous. We then integrated target capture data with legacy Sanger data to produce species-level phylogenetic trees of Sapindales families. Biogeographic analyses of the dated, species-level trees support Sundanian origin for Sapindales families, confirm the eastward bias in exchange from Sunda to Sahul, and highlight the importance of Wallacean emergence in facilitating the exchange. Most interestingly, the results indicate that for some lineages, an origin in Sunda and subsequent colonisation of Wallacea and Sahul explains the observed eastward bias in exchange, while for others, ancestors were present in Sahul, but extinction coincident with Miocene aridification likely contributed to the eastward exchange bias. This study has shed new light on Sapindalean evolution and the SSFE, and emphasises the importance of considering ancient evolutionary history when attempting to understand recent and current biogeographic processes.