Parsimony analysis of nucleotide sequences of the plastid gene rbcL and non-coding trnL-F region was used to examine phylogenetic relationships of 36 members of Zygophyllaceae, especially of the four genera forming subfamily Zygophylloideae (Zygophyllum, Fagonia, Tetraena and Augea). The two data sets were analyzed separately, and in combination. Results of the three analyses were largely in agreement and support previous division of Zygophyllaceae into five subfamilies. Zygophylloideae were further divided into five clades each with high bootstrap support, although the branches connecting these clades are poorly supported. Zygophyllum appears polyphyletic and may need further revision. The taxonomic positions of Morkillia, Sericodes, Pintoa, and Tribulopis are also clarified.

Communicating Editor: Kathleen A. Kron