Title：
Out of Africa: Phylogenomics and biogeography of Tribe Euphorbieae (Euphorbiaceae)
Authors：
Corresponding
Author：
Abiton O. Atolwa, Zhaohui Ran, Hager R. Belal, Elijah M. Mkala, Veronicah M. Ngumbau, Elijah Nyakudya, Shengwei Wang, Neng Wei*, Qingfeng Wang
Pubyear：
2026
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Journal of Systematics and Evolution
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Abstract：
The tribe Euphorbieae, the most species-rich lineage within the Euphorbiaceae family, comprises five genera across three subtribes (Anthosteminae, Neoguillauminiinae, and Euphorbiinae), with over 2000 species, predominantly in Euphorbia. While ecologically significant globally, critical gaps persist in resolving the species-level phylogeny of Euphorbieae and elucidating the biogeographic drivers of its global distribution. Among the total of 34 sampled species in Euphoroideae, 28 species were applied to represent all five genera in three subtribes of Euphorbieae, including 10 newly sequenced species representing 10 of the 11 extant species of Anthosteminae and Neoguillauminiinae, plus 18 representative Euphorbia (Euphorbiinae) species. Using plastome and nuclear ribosomal DNA (nrDNA) data sets, we reconstructed phylogenetic relationships, estimated the divergence times inferred ancestral areas, and analyzed diversification patterns. Our results strongly support Euphorbieae's monophyly and clarify sister relationships among subtribes. We present the first resolved species-level phylogeny for Euphorbieae (excluding the gigantic genus Euphorbia), revealing the tribe's evolutionary timeline, with instances of nuclear-plastid discordance suggestive of hybridization or incomplete lineage sorting. The crown age of Euphorbieae dates to approximately 62.11 million years ago (Ma) in the early Paleocene. Biogeographic analyses reveal the African origin at early Paleocene, followed by major dispersal events to Australasia, Asia, and the Neotropics. The combined plastome-nrDNA approach significantly enhanced phylogenetic resolution. These findings provide crucial insights into Euphorbieae's global out of Africa distribution pattern and contribute toward understanding the role of key innovations and climatic shifts in plant diversification.
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