PHYLOGENETIC ANALYSIS OF THE ZINGIBERALES BASED ON RBCL SEQUENCES

Morphological data have been used previously to construct phylogenies of the eight families of the Zingiberales, one of the most widely acce pted monophyletic groups of flowering plants. To provide additional su pport for phylogenetic relationships within the order, and placement o f the order among monocots, we present a parsimony analysis of DNA seq uences from the chloroplast-encoded gene, rbcL, for 21 species of Zing iberales and proposed relatives. Five analyses with equal, and differe ntial weights were performed. All analyses resulted in the same most p arsimonious tree for taxa within the Zingiberales and the immediate ou tgroup. The closest sister group to the Zingiberales based on these da ta is a clade containing Commelinaceae/Haemodoraceae/Pontederiaceae. T he tree topology within the order based on rbcL sequence data is diffe rent from previous morphological analyses. The order can be divided in to two sister groups, one containing the Costaceae and Marantaceae, an d the other, the remaining six families. All recognized families are m onophyletic with the exception of the Musaceae, which is paraphyletic with the Cannaceae. With trees one and two steps longer than the most parsimonious trees, phylogenetic resolution is rapidly lost, suggestin g that the phylogenetic utility of rbcL sequence data for the Zingiber ales is limited to interordinal and intrafamilial relationships.