The leafy spurges, Euphorbia subg. Esula, make up one of four main lineages in Euphorbia. The subgenus comprises about 480 species, most of which are annual or perennial herbs, but with a small number of dendroid shrubs and nearly leafless, pencil–stemmed succulents as well. The subgenus constitutes the primary northern temperate radiation in Euphorbia. While the subgenus is most diverse from central Asia to the Mediterranean region, members of the group also occur in Africa, in the Indo–Pacific region, and in the New World. We have assembled the largest worldwide sampling of the group to date (273 spp.), representing most of the taxonomic and geographic breadth of the subgenus. We performed phylogenetic analyses of sequence data from the nuclear ribosomal ITS and plastid ndhF regions. Our individual and combined analyses produced well–resolved phylogenies that confirm many of the previously recognized clades and also establish a number of novel groupings and placements of previously enigmatic species. Euphorbia subg. Esula has a clear Eurasian center of diversity, and we provide evidence for four independent arrivals to the New World and three separate colonizations of tropical and southern Africa. One of the latter groups further extends to Madagascar and New Zealand, and to more isolated islands such as Réunion and Samoa. Our results confirm that the dendroid shrub and stem–succulent growth forms are derived conditions in E. subg. Esula. Stem–succulents arose twice in the subgenus and dendroid shrubs three times. Based on the molecular phylogeny, we propose a new classification for E. subg. Esula that recognizes 21 sections (four of them newly described and two elevated from subsectional rank), and we place over 95% of the accepted species in the subgenus into this new classification.

Reconstructing phylogenetic relationships at the micro- and macroevoutionary levels within the same tree is problematic because of the need to use different data types and analytical frameworks. We test the power of target enrichment to provide phylogenetic resolution based on DNA sequences from above species to within populations, using a large herbarium sampling and Euphorbia balsamifera (Euphorbiaceae) as a case study. Target enrichment with custom probes was combined with genome skimming (Hyb-Seq) to sequence 431 low-copy nuclear genes and partial plastome DNA. We used supermatrix, multispecies-coalescent approaches, and Bayesian dating to estimate phylogenetic relationships and divergence times. Euphorbia balsamifera, with a disjunct Rand Flora-type distribution at opposite sides of Africa, comprises three well-supported subspecies: western Sahelian sepium is sister to eastern African-southern Arabian adenensis and Macaronesian-southwest Moroccan balsamifera. Lineage divergence times support Late Miocene to Pleistocene diversification and climate-driven vicariance to explain the Rand Flora pattern. We show that probes designed using genomic resources from taxa not directly related to the focal group are effective in providing phylogenetic resolution at deep and shallow evolutionary levels. Low capture efficiency in herbarium samples increased the proportion of missing data but did not bias estimation of phylogenetic relationships or branch lengths.

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Euphorbia subg. Esula (Euphorbiaceae) has recently been shown, using molecular analyses, to contain a clade with a disjunct distribution in Macaronesia, South Africa and the Eritreo‐Arabian region, and being primarily made up of members of sect. Tithymalus subsect. Pachycladae and sect. Tirucalli. To delimitate this disjoint group, we carried out phylogenetic analyses of the internal transcribed spacer (nrITS) using a broad sampling, with emphasis on subg. Esula. Subsequently, we carried out phylogenetic analyses focused on this clade using nuclear (ITS, ETS) and chloroplast (trnL‐trnF, psbA‐trnH, ycf3‐trnS, trnG, atpB‐rbcL, trnK‐matK, trnT‐trnL) markers, with the aim of resolving the phylogenetic relationships within the group and reconstructing its biogeographic history. Our results showed that sect. Tithymalus subsect. Pachycladae and sect. Tirucalli are polyphyletic. Section Aphyllis is recircumscribed to comprise the Pachycladae core clade and part of sect. Tirucalli. Low resolution within sect. Aphyllis and incongruences between nuclear and chloroplast phylogenies may be due to hybridization. Section Aphyllis should have originated in the Mediterranean area; its disjunct distribution is probably due to vicariance, resulting from fragmentation of a wider distribution area in North Africa caused by the aridification of the climate during the late Miocene‐Pliocene.

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