Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: The work conducted under this project includes efforts on the grass family (Poaceae) and on related monocot families. The portion devoted to monocot studies was initiated late in the year, when NSF funding was received. During 2008, collections were made for 80 key taxa that are to be examined during the study, with an emphasis on palms (Arecaceae). DNA isolations have proceeded, but analyses have not yet been conducted. Most effort for the year were devoted to the grass family (Poaceae). The phylogenetic analysis of this family focused on the critical tribe Poeae, within subfamily Pooideae. Five plastid-encoded genes and one nuclear-encoded gene have been sequenced from more than 150 representative taxa, and a well-resolved phylogenetic hypothesis based on the plastid genome. Most taxa in the analysis are drawn from subfamily Pooideae, and about half of these are from the tribe Poeae, which includes the fescues, bluegrasses, oats, timothy, and many other grasses of economic importance. Within Pooideae, relationships among tribes are as follows: The Poeae/Aveneae complex is sister of a clade that consists of Bromeae and Triticeae; Brachypodieae is sister of this clade; and the remaining tribes diverge from this large alliance in the following order: Diarrheneae; Meliceae; a complex group consisting of Phaenosperma, Duthiea, and other genera; Stipeae; Lygeeae plus Nardeae; and Brachyelytreae. Simultaneous analysis of morphological characters and the plastid-encoded genes highlights considerable incongruence between these two character sets among taxa of the Poeae/Aveneae complex, and a similar situation exists with respect to the plastid and nuclear genes. These results signify past hybridization among the taxa of this complex, indicating that the traditional division of the group into two tribes is artificial. The Poeae/Aveneae alliance includes many more species than the closely related tribe Triticeae, a polyploid complex that includes wheat, barley, rye, and about 300 other taxa. Details concerning patterns of hybridization among these taxa continue to be investigated. In the meantime, a comprehensive taxonomic system for the group, with 135 genera accommodated in 22 subtribes, within a single tribe, has been proposed to replace the traditional taxonomic system. Six of the subtribes have Aveneae-type plastid genomes, and this group includes Aveninae and Phalaridinae, as expected, but also Brizinae and Torreyochloinae, which lie within tribe Poeae in traditional systems. Similarly, the group with Poeae-type plastid genomes includes Loliinae and Poinae, as might have been expected, but also Alopecurinae and Airinae. Related studies have involved the analysis of relationships among monocots, with a focus on the complex order Poales (which includes the grasses), aimed at clarifying the ancestral characteristics and phylogenetic placement of the grass family and its closest relatives. PARTICIPANTS: Current efforts are proceeding within a multi-institutional collaboration, with funding through the ATOL program (Assembling the Tree of Life) of NSF. Major collaborators include Alejandra Gandolfo Nixon (Cornell University), Dennis Stevenson (New York Botanical Garden), Christopher Pires (University of Missouri), Jim Leebens-Mack and Wendy Zomlefer (University of Georgia), Tom Givnish and Cecile Ane (University of Wisconsin), and Sean Graham (University of British Columbia). TARGET AUDIENCES: The ongoing effort has systematic focus, as the goal is to establish a comprehensive and rigorously supported phylogeny of the monocots, a group that includes numerous food plants and others of great horticultureal and ecological importance, including grasses, palms, lilies, etc. The development of this phylogeny will contribute to studies in many areas, including systematics, ecology, genomics, plant breeding, and agriculture. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The grass family is includes numerous species of critical economic importance, ranging from species that yield food for human consumption (rice, wheat, maize, oats, sugarcane, etc.), and range and pasture grasses that are consumed by domesticated animals (fescues, timothy, etc.). Grasses also are important elements of erosion management, and the group includes many noxious weeds as well as the bamboos and plants that serve many other purposes. A robust phylogeny of the family contributes to the work of scientists in all of these fields by highlighting relationships among taxa of economic importance (positive and negative) and other lesser-known taxa, and thereby provides opportunities for breeding, plant introductions, and related actions. Grasses also include model taxa used in studies of genetics, physiology, and development, and a clarification of relationships among these taxa and other grasses with different features contributes to our understanding of the origins and phylogenetic distributions of critical genetic and organismal charateristics.
Publications
- No publications reported this period
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