Malahy, Mike , Doust, Andrew N. .
Is vegetative architecture phylogenetically meaningful across the grasses?
Grasses are easily recognized by their tussocky stems, with distichously arranged strap-like sheathing leaves, although, within this seeming uniformity, many arrangements of branching can be found. These include caespitose tussock grasses, grasses with rhizomes or stolons, and grasses that produce branches on the distal portions of erect or prostrate culms. These differences are ecologically significant, and have been capitalized on in the domestication of grass cereal and fodder crops. However, the control of plant architecture is affected by environmental conditions, and thus vegetative branching patterns have generally been considered to be too labile to contain signal of grass evolution. We decided to test this view by examining vegetative branching patterns in herbarium specimens of grasses representing all subfamilies and most tribes . A supertree was constructed from published grass phylogenies, and pruned to include only the taxa for which we had information on branching patterns. MacClade was then used to optimize branching patterns onto the supertree. As expected, the signal is noisy, and the overall pattern in the grasses appears complex, warranting further investigation. However, within this complexity there are some clear patterns of branching, and it appears that the predominant branching pattern of a group is also exploited in domestications within that group. Thus wheat and the other pooid cereal grasses show a pattern of multiple tillers, similar to the wild caespitose grasses in the Pooideae. Similarly, the reduction in tillers and axillary branches in panicoid crop grasses is part of a pattern of variation that is also found in many non-domesticated Panicoideae. Thus vegetative branching does carry phylogenetic signal, and the patterns of branching suggest that the form of domesticated grasses is related to the plant architecture of their wild relatives, even back to the tribe and subfamily level.
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1 - Oklahoma State University, Botany Department, Stillwater, OK, 74078, USA
Presentation Type: Poster:Posters for BSA Sections
Location: Event Tent/Cliff Lodge
Date: Monday, July 27th, 2009
Time: 5:30 PM