Format: ORAL

Else Demeulenaere1, J. Gordon Burleigh2, Tom Schils3, Stefanie M. Ickert-Bond4

1 University of Guam Center for Island Sustainability and Sea Grant, University of Guam, UOG Station, Mangilao, 96923, Guam 2 Department of Biology, University of Florida, PO Box 118525, Gainesville, FL 32611-8525, USA 3 Marine Laboratory, University of Guam, UOG Station, Mangilao, 96923, Guam 4 UA Museum of the North Herbarium and Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775-6960, USA

The Indo-Pacific region contains six of the 25 worlds biodiversity hotspots harboring many endemics. Serianthes consists of 17 island endemics and one littoral species, S. dilmyi. The endemics occur in the Pacific Islands, while S. dilmyi occurs in Malaysia, Indonesia, and the Philippines. Twelve of the 18 Serianthes species are listed on the Red List of Threatened Species. Although the circumscription of the genus has not been questioned, the phylogenetic relationships and diversification through time and space remain unclear. To study diversification we collected 81 samples across Serianthes Indo-Pacific distributional range and employed a targeted sequence capture approach and produced a time tree. We present the first robust, genus-wide, time-calibrated phylogeny and biogeographic hypothesis of Serianthes based on phylogenomics and densely sampling all species. We identified two well-supported clades representing two subgenera: One clade, subgenus Serianthes, comprising all taxa from Malesia, Papuasia and southern Micronesia, and the other clade, subgenus Hayunia, is uniting all taxa from Polynesia and northern Micronesia. Both Micronesian species, Serianthes nelsonii and S. kanehirae have disjunct populations with unique genotypes within their archipelagoes. Testing geographic range evolution under the DEC+j model, we inferred the most common ancestor originated in either Papuasia or New Caledonia during the Miocene. Most founder events in Serianthes happened during the Quaternary, aligning with the ages of the islands and supporting the progression rule of oceanic islands.Serianthes dilmyi crossed the Wallace Line and established populations in the Philippines and Indonesia. We may attribute this to its ability to thrive in mangrove habitats during the Quaternary era when sea levels were lower. Our study highlights the role of LDD during the diversification of Serianthes in the Indo-Pacific corroborating the important role of LDD using aAustro-Melanesia dispersal route similar to other tropical lineages such as Hernandia andPandanus.