Format: ORAL

Cssia Bitencourt1; Conal Aitken1; Matilda Brown1; Leonel Herrera-Alsina2; Olivier Maurin1; Natalia Przelomska1; Moabe F. Fernandes13; Mohammad Vatanparast1; Alessandro Rapini4; Mary Endress5; Sigrid Liede-Schumann6, David Goyder1; Brian Schrire1; Kyle Dexter7; Nicolai Nürk8; Jan Hackel19; Mike Gilbert1; Raquel Negrão1; Alexandre Zuntini1; Paul Kersey1; Ilia Leitch1; Eve Lucas1; Oscar A. Perez-Escobar1; Melanie J. Howes1; William J. Baker1; Eimear Nic Lughadha1; Alexandre Antonelli1,10,11; Félix Forest1

1 Royal Botanic Gardens, Kew, London, United Kingdom 2 University of Aberdeen, Aberdeen, United Kingdom 3 University of Exeter, Exeter, United Kingdom 4 Universidade Estadual de Feira de Santana, Feira de Santana, Brazil 5 Institute of Systematic Botany, Zürich, Switzerland 6 University of Bayreuth, Bayreuth, Germany 7 University of Edinburgh, Edinburgh, United Kingdom 8 University of Bayreuth, Germany 9 Philipps-Universität Marburg, Marburg, Germany 10 University of Gothenburg, Gothenburg, Sweden 11 University of Oxford, Oxford, United Kingdom

The expansion of arid environments following the Eocene-Oligocene climate transition is thought to have promoted increased species diversification rates across several plant lineages. In this study, we use the Apocynaceae as a model to assess whether a combination of biotic (e.g., lifespan and dispersal traits) and abiotic (e.g., climate and soil) predictors favoured diversification during the expansion of dry biomes. To accomplish this, we reconstructed a comprehensive time-calibrated phylogenetic tree for Apocynaceae using the Angiosperms353 bait set to establish a backbone. Subsequently, we merged all Apocynaceae species with sequence data (for ITS, trnL-F, and rps16) available on GenBank. Finally, distribution and trait data were compiled to test three hypotheses: [H1] Biome shifts between Apocynaceae species primarily occur from rainforest to savanna, whereas transitions between tropical and temperate environments are rare; [H2] Diversification in Apocynaceae was driven by "key synnovation" involving anemochory, presence of pollinia and climbing habit; and [H3] High speciation rates favoured the diversification of Apocynaceae lineages adapted to xeric environments. Our study suggests that lineages in more xeric environments exhibit higher speciation rates as they adapt to new, harsher conditions. These findings suggest that substrate, rather than biome, might be the primary factor regulating evolutionary rates in plants adapted to dry ecosystems.