Molecular phylogeny of Euphorbia subg. Esula sect. Aphyllis (Euphorbiaceae) inferred from nrDNA and cpDNA markers with biogeographic insights

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.