Many higher-level relationships within and among major monocot lineages remain unresolved or poorly supported in analyses based on sequence variation in rbcL, atpB, and 18S rDNA. We attempted to resolve some of these ambiguities by assembling a large number (ca. 200) of sequences of the large, rapidly evolving, chloroplast-encoded ndhF gene. Parsimony analyses resolved all major clades of monocotyledons, using Acorus as an outgroup. Within the traditionally difficult commelinoids, several sister-group relationships were resolved. Hanguana was sister to Zingiberales, and the latter was fully resolved: Zingiberaceae-Costaceae sister to Cannaceae-Marantaceae, and Musaceae-Heliconiaceae sister to Lowiaceae-Strelitziaceae. Dasypogonoids were closely related to Commelinales, and both were sister to Zingiberales/Hanguana near the base of the commelinoids, near Arecaceae. Rapateaceae was the closest relative of Poales and allied orders; Mayacaceae was sister to Bromeliaceae. Asparagales was resolved as the sister group to the commelinoids. Within the asparagoids, Themidaceae was sister to a large lineage including Agavaceae, Hyacinthaceae, Hostaceae, and Anthericaceae. Liliales was sister to the commelinoid-asparagoid clade. Within the lilioids, Calochortaceae and Liliaceae (both sensu Tamura) were monophyletic sister groups. Clintonia-Medeola was sister to Liliaceae s.s., while Tricyrtis was sister to Calochortus. Stemonoids formed a grade at the base of the commelinoids-asparagoids-lilioids; the alismatids were sister to all monocots sampled, excluding Acorus. Sequence variation in ndhF provides an additional, powerful set of molecular data with which to explore relationships and evolutionary patterns within the monocotyledons.

Key words: asparagoids, commelinoids, lilioids, Monocots, ndhF