A phylogenetic analysis of Poaceae tribe Poeae sensu lato based on morphological characters and sequence data from three plastid-encoded genes: evidence for reticulation, and a new classification for the tribe

摘要

Phylogenetic analysis of" variation in 18 morphological characters and structural and nucleotide .sequence variation in three plastid-encoded genes provides a well-supported hypothesis of relationships within /Wmr supertribe Poodae. This supertribe includes tribes Pome, Aveneae and Hainardieae, and other small tribes. Of the circa 135 genera that are assigned to this group, 57 were sampled, representing all major groups and inosi of the minor groups that have been recognised as tribes or subtribes. Historical and modern classifications of Poodae are reviewed and examined with respect to relationships detected by the phylogenetic analyses. Two major plastic! DNA lineages are detected, corresponding in general to groups traditionally recognised as Aveneae and Pome, but about one Fifth of the genera are placed in positions that conflict with traditional classifications. When comparing trees obtained from the morphological character set with those obtained from simultaneous analysis of the morphological and molecular character sets, the character distributions on the trees reveal substantial differences between homoplasy levels for several morphological characters. These results suggest the possibility of wide hybrid origins for some groups, especially the subtribe Airiruie. A revised classification is provided for Poodae, with all previously recognised tribes subsumed within a broadly circumscribed Poeae sensu lato, in which accepted genera are accommodated in 21 subtribes. Aveneae and smaller groups that have been recognised previously as tribes, including Hainardieae, Phalarideae, Phkeae and Seslerieac, are reduced to subtribes. Monophyly of many of the subtribes has at least, some molecular support, but other subtribes need further study, particularly involving nuclear genes, to better determine their relationships and to investigate possible hybrid origins.