Systematics of Capparaceae and Cleomaceae: an evaluation of the generic delimitations of Capparis and Cleome using plastid DNA sequence dataThis paper is one of a selection of papers published in the Special Issue on Systematics Research.

The phylogenetic relationships in Capparaceae and Cleomaceae were examined using two plastid genes, ndhF and matK, to address outstanding systematic questions in the two families. Specifically, the monophyly of the two type genera, Capparis and Cleome , has recently been questioned. Capparaceae and Cleomaceae were broadly sampled to assess the generic circumscriptions of both genera, which house the majority of species for each family. Phylogenetic reconstructions using maximum parsimony and maximum likelihood methods strongly contradict monophyly for both type genera. Within Capparaceae, Capparis is diphyletic: the sampled species belong to two of the five major lineages recovered in the family, which corresponds with their geographic distribution. One lineage contains all sampled New World Capparis and four other genera ( Atamisquea , Belencita , Morisonia , and Steriphoma ) that are distributed exclusively in the New World. The other lineage contains Capparis species from the Old World and Australasia, as well as the Australian genus, Apophyllum . Species of Cleome are scattered across each of four major lineages identified within Cleomaceae: (i) Cleome in part, Dactylaena , Dipterygium , Gynandropsis , Podandrogyne , and Polanisia ; (ii) Cleome droserifolia (Forssk.) Del.; (iii) Cleome arabica L., and Cleome ornithopodioides L.; and (iv) Cleome in part, Cleomella , Isomeris , Oxystylis , and Wislizenia . Resolution within and among these major clades of Cleomaceae is limited, and there is no clear correspondence of clades with geographic distribution. Within each family, morphological support and taxonomic implications of the molecular-based clades are discussed.