Format: ORAL

ngela Aguado-Lara1,2*, Isabel Sanmartn2, Johannes Le Roux3, Carlos Garca-Verdugo4,Sonia Molino5,6, Bettine Jansen van Vuuren7 Mario Mairal1.

1 Universidad Complutense de Madrid, Madrid, Spain. 2 Real Jardín Botánico (CSIC), Madrid, Spain. 3 Macquarie University, Sydney, Australia. 4 Universidad de Granada, Granada, Spain. 5 Universidad Autónoma de Madrid, Madrid, Spain 6 Universidad Europea de Madrid, Madrid, Spain. 7 University of Johannesburg, Johannesburg, South Africa.

The sub-Antarctic archipelagos are some of the most remote and semi-pristine insular habitats in the world. The diverse array of ages of these archipelagos, combined with the large distances between them and to the nearest landmasses, create an exciting area for exploring austral biogeography. This includes phenomena such as extreme long-distance dispersal and colonization, facilitated by marine currents across the Southern Hemisphere. Understanding these dynamics requires reconstructing the patterns and processes explaining biodiversity assembly in the sub-Antarctic archipelagos involved in the sub-Antarctic region. To better understand the biogeography of the sub-Antarctic region we examined four vascular plant species exhibiting different modes of dispersal which are widespread across the region and nearby austral continents, along with three species restricted to a very remote sub-Antarctic province: the Southern Indian Ocean Biogeographic Province (SIOBP). We generated and compiled nuclear and plastid DNA sequence data for each species and estimated phylogenetic relationships, divergence times, inter-island migration rates and island carrying capacities. Our findings reveal that the nearby continental landmasses (South America, Australia or New Zealand) acted as source areas for the dispersal of these widespread vascular plant species to the sub-Antarctic archipelagos. This connection persisted for millions of years, spanning from the Miocene to the present day, and may have been driven by the eastward-moving winds and water currents, supporting long-distance dispersal as a key biogeographic process in this region. In addition, the isolation of the sub-Antarctic archipelagos played a role in the origin of endemics restricted to remote islands. Overall, our study suggests that the sub-Antarctic islands have served as important biodiversity refuges from the Miocene to recent times, emphasizing the need to establish priority conservation plans for these habitats, particularly in light of rapid climate change throughout this region.