Monocot relationships: an overview.

In 10 years, the monocots have gone from being one of the least studied and most phylogenetically misunderstood groups of the angiosperms to one of the best characterized. Based on analyses of seven genes representing all three genomes, the following clades have high bootstrap support: Acorales (with the single genus Acorus) is sister to the rest of the monocots, followed successively by Alismatales (including Araceae and Tofieldiaceae), Petrosaviales, Dioscoreales/Pandanales, Liliales, Asparagales, and finally a polytomy of Arecales, Commelinales/Zingiberales, Dasypogonaceae, and Poales. Many of these results also have support from at least some morphological data, but some are unique to the trees created from DNA sequence data. Monocots have been shown in molecular clock studies to be at least 140 million years old, and all major clades and most families date to well before the end of the Cretaceous. More data are required to clarify the positions of the remaining unclearly placed orders, Asparagles, Liliales, and Arecales, as well as Dasypogonaceae. More sequences from the nuclear and mitochondrial genomes are also needed to complement those from the plastid genome, which is the most sampled and thus far most pattern-rich.