Format: ORAL

Laura Holzmeyer1,2, Frank Hauenschild2,3, Alexandra N. Muellner-Riehl2,4

1 IRD, UMR DIADE, Université de Montpellier, Montpellier, France 2 Department of Molecular Evolution and Plant Systematics & Herbarium (LZ), Institute of Biology, Leipzig University, D-04103 Leipzig, Germany 3 Centre for Teacher Training and School Research, Leipzig University, D-04317 Leipzig, Germany 4 German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, D-04103 Leipzig, Germany

Dysoxylum s.l. had long been speculated to be a polyphyletic taxon. Recently, six strongly supported clades within the group were exhibited based on phylogenetic analyses employing several DNA marker regions. To ensure monophyly, five previously recognized genera (Didymocheton Blume, Epicharis Blume, Goniocheton Blume, Prasoxylon M.Roem. and Pseudocarapa Hemsl.) were reinstated, and Dysoxylum s.s. Blume ex Raspail was re-defined. This taxonomic revision, based on the most extensively sampled molecular phylogenetic tree of this group established so far, and morphological characters, resulted in the re-assignment of 94 presently acknowledged Dysoxylum species, generating forty-five new combinations and complementary lectotypifications as required. This taxonomic groundwork set the stage for biogeographic exploration. Our sampling encompassed 75% of the Dysoxylum s.l. species diversity, covering the entire distribution range and all major lineages. Results showed that Dysoxylum s.l. originated and firstly diversified in the western part of its current distribution range (including Indochina) during the Miocene to Pliocene, followed by an overall eastern range expansion towards Malesia, Australia and the Southwest Pacific in the Pliocene. This southeastward expansion into Wallacea and Australia coincided temporally with the convergence of the Asian and Australian tectonic plates and followed the expected dispersal directionality bias. We were able to establish long-distance dispersal as the primary mechanism shaping the current distribution. Furthermore, we identified two dispersal pathways into the Southwest Pacific: one from New Guinea and the Solomon Islands to Fiji, and another one from New Zealand to Fiji. Remarkably, Fiji served as an important secondary source area for dispersal into the Southwest Pacific from both New Guinea through the Solomon Islands, as well as from New Zealand.