XVI International Botanical Congess

Duplicate gene rooting of the angiosperm tree based on simultaneous analysis of phytochrome (PHY) A and C unambiguously places the root at Amborella. Analysis of the gene pair, which diverged prior to the origin of angiosperms, yields an unrooted network wherein PHYA and PHYC subtrees connect by a single branch. Topologies of the subtrees suggest that Nymphaea + Cabomba, Ceratophyllum, Austrobaileya + Illicium, and Chloranthus also diverged early. Unrooted analysis of a second PHY pair, PHYB and PHYE, resolves three principal clades. They are PHYB of Amborella, Illicium,, and Austorobaileya, PHYB of other angiosperms, and all PHYE. PHYB occur in all angiosperms, PHYE are not known from Amborella, Nyphaeales, monocots, nor Piperales. Earliest PHYE are found in Illicium, Ceratophyllum, and Chloranthus, Illicium PHYE is sister to all other PHYE. Study of PHYE-like sequences in Aristolochiales may clarify the lack of PHYE in Piperales, and may help resolve relationships among Piperales, Aristolochiales, and monocots.