Euphorbia in Southern Africa

This book presents a new account of Euphorbia in southern Africa. Euphorbia is the second largest genus of plants in the world. Southern Africa enjoys a high diversity in Euphorbia and 170 species occur here naturally. Of these 170 species, 128 or 74% are endemic. Where most species of Euphorbia in the northern hemisphere are herbs or shrubs, most of those in southern African are succulent. These succulents range from small, almost geophytic forms where the tuber is larger than the above-ground parts to huge trees 6 to 15 m or more in height. Many of them are spiny. There are also small numbers of herbaceous species in southern Africa and many of these are also dealt with here. The last account of the succulent species for southern Africa was published in 1941 and much new data has accumulated since then. Our understanding of the relationships of the species in Euphorbia has also been greatly enhanced by recent analyses of DNA-data, which led to new and unexpected results. From this new information an entirely new classification was developed, in which Euphorbia was divided into four subgenera. This provides the taxonomic framework for the presentation of our species here. Around ten new species have been described and these are presented in detail for the first time.

This monograph is made up of two volumes. Volume 1 contains an extensive introductory chapter with an overview of the genus in the region, emphasizing many of its important and distinctive features. This is followed by Chapter 2, which deals with subgenus Athymalus. Of the four subgenera, this one is by far the most diverse in southern Africa, with 80 species. Volume 2 contains Chapters 3 (subg. Chamaesyce, 34 species), 4 (subg. Esula, 11 species) and 5 (subg. Euphorbia, 45 species), as well as an additional Chapter 6 covering the remarkable diversity of subg. Euphorbia in Moçambique. Each of Chapters 2 to 5 includes a key to all the