Format: ORAL

PalomaRuiz de Diego1*, Patricia Barbera´2, ngela Aguado-Lara1, Irene Villa-Machi´o1, Tamara Villaverde3, Ricarda Riina1 Isabel Sanmarti´n1

1 Real Jardín Botánico (RJB), CSIC, Madrid, Spain 2 Missouri Botanical Garden, St. Louis, Missouri, USA 3 Universidad Rey Juan Carlos, Madrid, Spain

The Odd-Man-Out pattern describes the lower plant diversity observed in continental tropical Africa compared to other tropical regions. We examine long-standing hypotheses behind this pattern by adopting a model-clade approach that combines in-depth knowledge of small-scale clade studies with the power of family-wide meta-analysis. We focus on 31 genera of Euphorbiaceae (~550 species), grouped into 19 clades. Our workflow involves the revision of each genus alpha-taxonomy and the compilation of information about species traits, distribution, and ecology; the generation of phylogenetically informative sequence data from 431 low-copy nuclear genes, obtained using target sequencing (Hyb-Seq) and a taxon-specific bait kit; and finally, the integration of the assembled trait, ecological, biogeographic, and phylogenomic data to explore biological processes working at the clade-level, and general drivers acting clade-wide on Afrotropical lineages. Based on ~78% of the target species and all focal genera, we produced the first phylogenomic time-tree for the African Euphorbiaceae, including representatives of the three subfamilies Acalyphoideae, Crotonoideae, and Euphorbioideae. An ancient stem age (54-26 Ma) was inferred for the smallest genera (less than 10 species), predating the global climate cooling that followed the Paleogene. Diversification rate analyses using episodic birth-death models and an empirical strategy to account for missing species revealed a negative diversification rate between 23 and 5 Ma, which corresponds with a period of severe aridification in Africa. Paleoclimate niche projections showed climatically suitable areas across southern and eastern Africa for many genera, which disappeared after the Pliocene. Taken together, this evidence points to climate-driven extinction as the most likely process to explain the Odd-Man-Out pattern in African Euphorbiaceae. Frequent dispersal from Madagascar was an additional process involved in shaping diversification patterns, as revealed by an 80%-complete species tree for the mega-diverse genus Croton.