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.

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The present paper updates the taxonomy of Euphorbia subsect. Myrsiniteae for the Flora of Iran since the publication of Flora Iranica in 1964. We provide a key, descriptions, distribution maps and illustrations for the seven taxa of the subsection occurring in the country. The presence of E. monostyla and the absence of E. rigida is confirmed. The distribution of E. spinidens, E. myrsinites, E. marschalliana subsp. marschalliana and E. marschalliana subsp. armena is updated, and E. marschalliana subsp. woronowii is considered a synonym of E. marschalliana subsp. marschalliana.

We studied leaf anatomy, mitotic chromosomes and pollen grains of nine species of Euphorbia (E. chamaesyce, E. granulata, E. indica, E. humifusa, E. maculata, E. petiolata, E. prostrata, E. serpens and E. nutans) out of the 15 species of Euphorbia subg. Chamaesyce present in Iran. We compared our results with two species of subg. Esula sections Tythymalus and Helioscopia (E. peplus and E. helioscopia). Our anatomical survey identified the Kranz bundle sheath as a distinct anatomical character for subgenus Chamaesyce sect. Anisophyllum, differentiating this from E. petiolata of subg. Chamaesyce sect. Cheirolepidium. Based on type of abaxial epidermis cell walls, species were classified into three groups including species with zigzagged, sinuous and intermediate (zigzagged-sinuous) walls. Chromosome numbers for four species were reported for the first time from Iran, and 2n=32 is the first report for E. indica. Three shapes of pollen grains were determined: oblate spheroidal, prolate spheroidal and subprolate. A tectate perforate exine ornamentation was detected in almost all of the species.