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Molecular systematic studies in commelinid monocots Saarela, Jeffery Michael


To clarify phylogenetic relationships among the major commelinid monocot lineages, among families in the orders Commelinales and Poales, and among grass subfamilies (Poaceae), I surveyed multiple plastid protein-coding regions and associated noncoding regions from exemplar taxa sampled broadly across these lineages. I also characterized phylogenetic relationships in the grass genus Bromus, using two plastid regions and a nuclear region. In commelinids, phylogenetic inferences using parsimony and likelihood are generally congruent, and my analyses provide strong support for many aspects of commelinid relationships. Commelinales and Zingiberales are sister taxa, but the positions of Arecales and Dasypogonaceae are not clear. Commelinales includes a Commelinaceae-Hanguanaceae clade and a (Philydraceae, (Haemodoraceae-Pontederiaceae)) clade. Philydrella is the sister group of the rest of Philydraceae. Poales includes a cyperid clade (Thurniaceae, . (Cyperaceae-Juncaceae)), and a 'core Poales' clade consisting of a graminid clade (Flagellariaceae, (Joinvilleaceae, (Ecdeiocoleaceae-Poaceae))) and a restiid clade (Anarthriaceae, (Centrolepidaceae-Restionaceae)). Ecdeiocoleaceae are moderately supported as the sister group of Poaceae in analyses in which taxon.sampling is most dense. The position of the aquatic Mayacaceae differs between parsimony and likelihood analyses, perhaps reflecting a long-branch artifact. Rapateaceae are part of a clade that includes all Poales except Bromeliaceae and Typhaceae, and the positions of these latter two families at the base of the Poales subtree are unresolved. Within Poaceae, Anomochlooideae and the BEP clade are supported strongly, Anomochlooideae, Pharoideae, and Puelioideae are the successive sister groups (respectively) of the remaining grasses, and Bambusoideae and Pooideae are sister taxa. A generally accelerated substitution rate in Poaceae plastid genomes is shared with most, but not all, Poales lineages. Independent analyses of plastid and nuclear ribosomal data in Bromus indicate that several traditionally recognized sections are monophyletic, but sect. Bromopsis is not. There is some evidence of incongruence between plastid and nuclear linkage groups in Bromus, particularly with respect to relationships among major lineages. Based on plastid data, the dwarf aquatic family Hydatellaceae are not commelinids or (more broadly) monocots, but the sister group of water lilies (Nymphaeales), a result corroborated by nuclear data and morphology.

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