Phylogenetic analyses of Pilosocereus (Cactaceae) inferred from plastid and nuclear sequences.

Pilosocereus is a large genus of Cactaceae with 42 species of columnar cacti distributed in the Americas. In this work we investigate the phylogenetics and evolutionary history of Pilosocereus based in plastid and nuclear DNA sequences. We use phylogenetic trees obtained as a basis to analyse infrageneric relationships and to study the evolution of selected morphological characters and geographical distribution in the group. Thirty-three species of the genus were sampled and five molecular regions were selected, four non-coding intergenic spacers of plastid DNA (trnS-trnG, psbD-trnT, trnL-trnT, petL-psbE) and one nuclear low-copy gene (phytochrome C). The phylogenetic analyses obtained point to a paraphyletic Pilosocereus, with P. bohlei and P. gounellei emerging nested in a clade of outgroup species (i.e. other genera of Cereinae). However, the majority of species of the genus form one well supported clade (excluding P. bohlei and P. gounellei) corresponding mostly to Pilosocereus subgenus Pilosocereus. Evidence indicates that the ancestor of Pilosocereus subgenus Pilosocereus clade was a shrub with a straight floral tube occurring in Brazil and the ancestor of Pilosocereus subgenus Gounellea was a shrub with a curved floral tube also occurring in Brazil. The ancestral distribution in central and eastern Brazil resulted in the diversification of most lineages in the same area, whereas the P. leucocephalus clade was able to disperse through the Amazonian areas and diversify further north and reach Central and North America. [ABSTRACT FROM AUTHOR]