Phylogenetics of Paniceae (Poaceae)

Paniceae demonstrate unique variability of photosynthetic physiology and an atomy, including both non-Kranz and Kranz species and all subtypes of the l atter. This variability suggests hypotheses of independent origin or revers als (e.g., from C-4 to C-3). These hypotheses can be tested by phylogenetic analysis of independent molecular characters. The molecular phylogeny of 5 7 species of Paniceae was explored using sequences from the grass-specific insert found in the plastid locus rpoC2, Phylogenetic analyses confirmed so me long-recognized alliances in Paniceae, some recent molecular phylogeneti c results, and suggested new relationships. Broadly, Paniceae were found to be paraphyletic with Andropogoneae, Panicum was found to be polyphyletic, and Oplismenus hirtellus was resolved as the sister group to the remaining ingroup species. A particularly well-supported clade in the rpoC2 tree incl uded four genera with non-Kranz species, and three with distinctively keele d paleas. As previously suggested, the PCK (phosphoenol pyruvate carboxykin ase) C-4 subtype arose once within Paniceae. All clades with non-Kranz spec ies had Kranz ancestors or sister taxa suggesting repeated loss of the Kran z syndrome.