Format: ORAL

Irene Masa-Iranzo1, Isabel Sanmartn1, Božo Frajman2, Andrea S. Meseguer1, and Ricarda Riina1

1 Real Jardín Botánico (RJB), CSIC, Madrid, Spain; 2 University of Innsbruck, Innsbruck, Austria

Euphorbia subgenus Esula Pers. is one of the four lineages of the megadiverse genus Euphorbia, and comprises over 485 annuals or perennials, including dendroid shrubs and pencil-stemmed succulents. While the group is primarily a northern temperate radiation it is most diverse in the Irano-Turanian and Mediterranean regions, but taxa also occur in Africa, Asia, and the temperate New World. We assembled the largest taxon sampling of E. subg. Esula to date (322 spp.), representing its entire geographic range. We updated previous phylogenetic analyses, which confirmed the current sectional classification of the group. We also estimated divergence times and reconstructed ancestral ranges using Bayesian methods. This framework allowed us to characterize the magnitude of extinction and speciation events that have shaped the extant diversity and present distribution of this subgenus. We also explored the influence of changes in life form/history in the diversification and the present altitudinal ranges of E. subg. Esula. Our results show the divergence of E. subg. Esula from its sister clade (the three other subgenera) c. 47 Mya, and diversification within this group c. 41 Mya. Biogeographic analyses suggest an ancient origin of the group in the Western Palearctic, where it steadily diversified over millions of years, before the subgenus dispersed to other regions recently. The group underwent parallel events of recent radiations coupled with life history changes, from annual to perennial. Our findings suggest a positive correlation between perenniality and high elevations. These results support that the recent rapid diversification of E. subg. Esula is associated with the evolutionary shift to perennial life forms, which allowed colonization of montane habitats and global range expansion beyond the Western Palearctic.