PHYLOGENETIC-RELATIONSHIPS OF THE BROMELIIFLORAE-COMMELINIFLORAE-ZINGIBERIFLORAE COMPLEX OF MONOCOTS BASED ON RBCL SEQUENCE COMPARISONS

Four cladistic hypotheses were constructed for Dahlgren's Bromeliiflorae-Commeliniflorae-Zingiberiflorae complex, primarily from suggestions of affinities according to morphology-based treatments: (i) Dahlgren's treatment of the families is correct; (ii) the Bromeliaceae and Zingiberales are sister groups; (iii) the complex is monophyletic, with the Arecaceae as the closest outgroup; and (iv) a clade that contains the Bromeliaceae and Commelinaceae is monophyletic. These four hypotheses were evaluated using sequence data from the chloroplast gene, rbcL, that codes for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase. Results were compared between a broad analysis of 499 rbcL sequences and a smaller data set that included only families of the complex plus the Arecaceae (52 taxa). The larger data analysis supported hypothesis (iii), minus the Velloziaceae. However, hypotheses (i) and (ii) were not supported, and support for hypothesis (iv) was equivocal. Three decisions on classification can be made based on the results of this study: (i) submerge the Bromeliiflorae into the Commeliniflorae; (ii) remove the Velloziaceae from the complex; and (iii) remove the Cyclanthaceae and Pandanaceae from the Areciflorae.