Phylogenetic Relationships of Pilosocereus (Cactaceae) and Taxonomic Implications

The aim of this paper was to investigate the phylogenetic relationships within Pilosocereus (Cactaceae, Cactoideae), one of the most emblematic genera of cacti of the Neotropical dry woodlands. The genus includes 42 species and eight subspecies placed in two subgenera: Pilosocereus subg. Pilosocereus and Pilosocereus subg. Gounellea. We used an expanded sampling and a broad coverage of genomic regions (psbD-trnT, trnL-trnT, petL-psbE, trnS-trnG, ycf1 and PhyC) resulting in an aligned concatenated matrix of 4563 bp length. Maximum parsimony and Bayesian analyses recovered a non-monophyletic Pilosocereus as well as four consistently non-monophyletic species. We propose taxonomic changes to accommodate para- or polyphyletic taxa including the resurrection of three species, three new synonyms, two new names and a new circumscription for Pilosocereus with 42 species and four subspecies. Xiquexique is proposed as a new genus characterized by molecular and morphological characters, composed of three species formerly positioned in P. subg. Gounellea.