Plio-Pleistocene diversification of Cereus (Cactaceae, Cereeae) and closely allied genera

Abstract

Cereus (Cactaceae; Cereeae) comprises c. 30 predominantly South American species distributed among the subgenera Oblongicarpi, Ebneria, Mirabella and Cereus. To study patterns of diversification in time and space, the trnStrnG plastid region was sequenced from representatives of Cereus and the closely related genera Cipocereus and Praecereus. For a subset of our total samples, we also obtained sequences of the low-copy nuclear gene photoreceptor phytochrome C (PHYC). Phylogenetic analyses showed Cereus to be paraphyletic, with Cipocereus as sister to subgenus Mirabella. Apart from Mirabella, the subgenera of Cereus are also not monophyletic. The diversification of the ingroup lineage began around the Plio-Pleistocene transition, and most species diversification events occurred during the mid to late Pleistocene. Biogeographic analysis determined the region of the Cerrado biome, in central Brazil, as the most likely ancestral range of the ingroup. Furthermore, more recent vicariance and dispersion events were identified for internal branches. Overall, our results support the notion that Neogene orogenic events and Pleistocene climatic oscillations contributed to shaping the diversification of modern lineages of South American biota.