BARBER, JANET C.1*, LILIANA M. GIUSSANI2, and ELIZABETH A. KELLOGG1. 1Department of Biology, University of Missouri, 8001 Natural Bridge Road, St. Louis, MO 63121; 2Instituto de Botanica Darwinion, Labarden 200 C.C. 200, San Isidro, Buenos Aires, Argentina 1642. - Phylogeny of Poaceae subfamily Panicoideae based on sequences of phytochrome B, a low-copy nuclear gene.
We are using sequences of phytochrome B, a low-copy nuclear gene, to
reconstruct phylogenetic relationships within Poaceae subfamily
Panicoideae. Results corroborate relationships found by two earlier
studies based on chloroplast markers (ndhF; combined sequences of the
trnL intron and the trnL-trnF intergenic spacer regions). The Old
World genus Danthoniopsis is excluded from the Panicoideae.
Tribe Andropogoneae, including Arundinella, is monophyletic.
Tribe Paniceae is also monophyletic, but resolution within the tribe
differs from that of the chloroplast phylogenies. The chloroplast
trees recovered two major clades corresponding to chromosome number,
with one clade comprising the x = 10 taxa and a second clade composed
of taxa with a base number of x = 9. The nuclear tree also recovers a
monophyletic x = 9 clade but it is nested within a paraphyletic x = 10
group. This apparent paraphyly may be a sampling artifact, since our
sampling to date within this group is minimal. Relationships within
the x = 9 clade correspond to groups sharing the same C4
photosynthetic subtype, with one group using NAD-malic enzyme, one
using PCK, and a third using NADP-malic enzyme (the
"bristle" clade). All studies have demonstrated multiple
origins of the C4 photosynthetic pathway within the Panicoideae,
leading to the unexpected revelation that chromosome number is a
better predictor of phylogenetic relationships than is photosynthetic
Key words: Panicoideae, phytochrome B, Poaceae