Format: ORAL

Kenneth J. Wurdack1, Otvio Luis M. da Silva2,4, Ricarda Riina3, Ins Cordeiro4, Lynn J. Gillespie5,Warren M. Cardinal-McTeague6, Federico Fabriani7, Olivier Maurin7, Sue Zmarzty7, Alexandre Zuntini7, Felix Forest7, William Baker7

1 National Museum of Natural History, Smithsonian Institution, Washington, DC, USA 2 Instituto de Pesquisas Ambientais, São Paulo, Brazil 3 Real Jardín Botánico (RJB), CSIC, Madrid, Spain 4 Universidade de São Paulo, São Paulo, Brazil 5 Canadian Museum of Nature, Ottawa, Ontario, Canada 6 University of British Colombia, Vancouver, British Colombia, Canada 7 Royal Botanic Gardens, Kew, Richmond, United Kingdom

Resolving relationships among Euphorbiaceae, the largest and least understood family of Malpighiales, is challenging due to the familys morphological diversity, ancient origins, and pantropical distribution. Molecular phylogenetic studies from the early 2000s discovered (but could not resolve among) seven major lineages of uniovulate Euphorbiaceae and identified widespread conflicts with existing suprageneric classifications. Our phylogenomic results from the Plant and Fungal Trees of Life (PAFTOL) project, which sampled 150 of the ca. 230 genera of Euphorbiaceae using Angiosperms353 target sequence capture, are largely congruent with the prior few-gene studies and offer improved backbone resolution. They support four subfamily-level clades including the previously unclear monophyly of Acalyphoideae, with Erismantheae as its first-diverging lineage. The monophyly of Crotonoideae is also strongly supported, with four major lineages plus a novel, isolated placement for monotypic Klaineanthus. The resolution of several critical deep nodes remains problematic, including among subfamily clades, which limits our understanding of the early evolution of major traits such as latex/laticifers, petals, and pollen types. In addition, the relationships within Malpighiales of hard-to-place parasitic Rafflesiaceae remain unclear and affect whether Peraceae could be reunited with Euphorbiaceae (as Peroideae). Hippomaneae s.l., the greatest remaining tribal systematics problem, represents a gap in our taxonomic sampling, with only nine of ca. 40 genera sampled. Striking variations in diagnostic morphological traits were observed across clades, including contrasting life history strategies, plant defenses, floral attributes, and specialized reproductive biology (e.g., changes in seed size and dispersal mode). The advances presented here are major steps towards a well-resolved generic phylogeny that would underlie a new classification for Euphorbiaceae and support future studies on the evolution of the astonishing diversity of the family and its biogeographic history.