Phylogeny and circumscription of Cephalocereus (Cactaceae) based on molecular and morphological evidence

Cephalocereus, Neobuxbaumia, and Pseudomitrocereus (Cactaceae, Cactoideae, Echinocereeae) are related genera of columnar cacti native to Mexico with current ambiguous circumscription. We applied maximum parsimony and Bayesian inference methods to reconstruct the phylogeny of the Cephalocereus group using molecular data from seven chloroplast regions (petL-psbE, psbA-trnH, rpl16, rpl32-trnLUAG, trnL-F, trnQrps16, andycf1), simple coded indels, and 46 structural characters. The Cephalocereus group was recovered as monophyletic with high support values, whereas Neobuxbaumia appeared as paraphyletic, due to the polyphyly of Cephalocereus and the derived position of Pseudomitrocereus within this group. Topology was mostly congruent among the different phylogenetic methods explored, and three pervasive clades were observed. Two structural characters were confirmed as synapomorphies for the Cephalocereus group: prismatic crystals in the dermal system and a perianth woody cap persistent in the ...