A new subgeneric classification for Euphorbia (Euphorbiaceae) in southern Africa based on ITS and psbA-trnH sequence data

Abstract

We use data from the internal transcribed spacer (ITS) region of the nuclear rDNA cistron and the chloroplast psbA–trnH intergenic spacer to reconstruct the phylogenetic relationships among southern African species of Euphorbia. The results indicate that major re–organization is necessary of the groupings within Euphorbia that have been recognised in the past, since most of them turn out to be polyphyletic. Furthermore, in its present circumscription, Euphorbia itself is not monophyletic, nor do the southern African species form a monophyletic group. Both datasets show that the southern African species fall into four major groups, which we recognise as subgenera: Chamaesyce Raf., Esula Pers., Euphorbia and Rhizanthium (Boiss.) Wheeler. To accommodate the southern African species, subg. Chamaesyce is divided into sect. Chamaesyce, sect. Frondosae Bruyns, sect. nov., sect. Articulofruticosae Bruyns, sect. nov. and sect. Espinosae Pax & Hoffm. Subgenus Euphorbia is divided into sect. Euphorbia, sect. Monadenium (Pax) Bruyns, sect. Goniostema H. Baill. ex Boiss. and sect. Tirucalli Boiss. To re–establish the monophyly of Euphorbia, the genera Endadenium L. C. Leach, Monadenium Pax and Synadenium Boiss. are reduced to synonymy under Euphorbia subg. Euphorbia sect. Monadenium and the species are all transferred to Euphorbia. Consequently the subtribe Euphorbiinae now consists of the single, very large, very widely distributed and very diverse genus Euphorbia. Three of the subgenera (Chamaesyce, Esula, Euphorbia) are nearly cosmopolitan, showing the great age and wide extent of the radiation that has occurred within Euphorbia. The remaining subg. Rhizanthium is mainly African.

Phenetic Analysis of Certain Taxa of Euphorbiaceae Grown in Egypt

“…Anatomically, they are characterized by absence of glandular trichomes. The present data confirmed those of Steinmann (2003), Bruyns et al (2006) and APG III (2009).…”

“…and Synadenium (4 spp.) (Bruyns et al, 2006). Steinmann (2003), Bruyns et al (2006) and APG III (2009) works which based on molecular data consider the genus Pedilanthus as a synonym of Euphorbia and make a valid name Euphorbia tithymaloides.…”

“…and Synadenium (4 spp.) (Bruyns et al, 2006). The genera Endadenium, Monadenium and Synadenium are reduced to synonymy under Euphorbia and the species are all transferred to Euphorbia.…”

“…al., 2006). Steinmann (2003), Bruyns et al (2006) and APG III (2009) works which based on molecular data reduce the genus Synadenium as a synonym of Euphorbia and make a valid name Euphorbia pseudograntii. In the present study E. pseudograntii grouped with other Euphorbia species on the basis of the following morphological data viz.…”

EuphORBia: a global inventory of the spurges

“…Recent molecular studies (Steinmann & Porter 2002, Bruyns et al 2006, Steinmann et al 2007 showed that the genus Euphorbia is only monophyletic if numerous generic segregates of Euphorbia are included within it, such as Chamaesyce, Cubanthus, Monadenium, Pedilanthus, Poinsettia, and others. In this broad sense, Euphorbia includes at least 2 000 species, and is therefore one of the largest non-apomictic genera of flowering plants; only few genera of phanerogams include more species, e.g., Astragalus (Leguminosae).…”