Members of the genus Pereskia (17 species) exhibit a number of plesiomorphic characters for the family Cactaceae such as shrubby habit, non-succulent or partially succulent leaves, and in some species, nearly superior ovaries. In addition, the members of this genus also show a transition from perigynous flowers with half-inferior ovaries to those species having true receptacular epigyny (the predominant condition in the Cactaceae). To examine this and other morphological transitions in the presumably basal cactus lineages, a well resolved phylogeny was sought to provide the basis for interpreting anatomical/structural innovations and polarizing character state changes. Interspecific relationships within Pereskia were inferred using combined datasets from cpDNA restriction-site data, together with sequence data from non-coding regions of the plastid genome, including the psbA-trnH, trnL-trnF and trnT-trnL intergenic spacers, and the rpl16 intron. Maximum parsimony analyses netted a well-supported phylogeny for Pereskia, which identified three major clades, these corresponding to presumed major migration routes from a central Andean origin to two centers of diversification: one in central and eastern Brazil, and the other in southern Central America and the Caribbean. Phylogenetic evidence for the transition from perigyny in the majority of Pereskia species to epigyny in P. bleo, P. portulacifolia, P. ziniiflora and P. quisqueyana was observed. These taxa constitute a strongly supported monophyletic clade, suggesting that receptacular epigyny has occurred only once in the genus. The sister group relationship for the yellow flowered species of Pereskia (P. aureiflora and P. guamacho) was also confirmed, despite their widely disjunct distribution, further suggesting that migration has played an important role in speciation events within this genus.

Key words: Cactaceae, Pereskia, phylogeny