A phylogenetic analysis of Zygophyllaceae R Br based on morphological, anatomical and rbcL DNA sequence data

Zygophyllaceae R.Br. are a widespread family of some 25 genera from the arid tropics and subtropics. Taxonomic relationships of the family have been subject to a wide diversity of opinion and familial status has been proposed for subfamilies Peganoideae, Nitrarioideae, Tribuloideae, and Balanitoideae. The plastid gene rbcL for 20 species of Zygophyllaceae was analysed in two separate data matrices, one containing members of Zygophyllaceae sensu lalo and representatives of several putatively related families, and one containing only members of the family sensu stricto. A morphological and anatomical data matrix for Zygophyllaceae s.s. was also analysed, and a combined analysis of molecular and nonmolecular data was conducted. Zygophyllaceae s.s. form a monophyletic clade with no;close relationships to any other group apart from the monotypic family Krameriaceae. They divide into five monophyletic lineages: one corresponding to Morkillioideae; one consisting only of Seetzenia; and three which derive from division of Zygophylloideae. Balanites consistently appears within the tribuloid clade. Peganum, Malacocarpus and Nitraria appear widely separated from Zygophyllaceae s.s. and close to members of Sapindales. Recognition of Peganaceae and Nitrariaceae is recommended, as is a recircumscription of Zygophyllaceae s.s. to comprise five subfamilies. (C) 1996 The Linnean Society of London