Molecular phylogenetics of the leafy cactus genus Pereskia (Cactaceae)

Members of Pereskia exhibit some presumably plesiomorphic characters for the Cactaceae including shrubby habit, non-succulent or partially succulent leaves, and in some species, nearly superior ovaries. In addition, the members 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 interspecific relationships within Pereskia we utilized cpDNA restriction-site data and sequences from two non-coding regions of the plastid genome-the psbA-trnH intergenic spacer and the rpl16 intron. Maximum parsimony and Bayesian analyses identified three major clades: a clade containing the widespread P aculeata and the Andean species, a clade containing six species found primarily in southeastern Brazil, Paraguay, Uruguay, Argentina, and Bolivia, and a third clade centered in southern Central America and the Caribbean. The relationship between these three clades and the rest of the Cactaceae remains unresolved, but our data do suggest that Pereskia may be paraphyletic. The sister taxon relationship for the yellow flowered species of Pereskia (P aureiflora, P guamacho) was also confirmed, despite their widely disjunct distribution.