XVI International Botanical Congess

Recent studies based on morphology, rbcL sequences, 18S rDNA sequences, cpDNA internal transcribed spacers, and mtDNA sequences suggest conflicting relationships among the major groups of extant seed plants. Of particular interest has been the position of the Gnetales relative to the angiosperms. The Gnetales have alternatively been shown as the sister group to the angiosperms, the sister to the conifers within a monophyletic gymnosperms, and a basal lineage within the seed plants. Additional data are needed to address the position of the Gnetales and to identify the sister group to the angiosperms. We conducted phylogenetic analyses of entire 26S rDNA sequences from cycads, Ginkgo, conifers, Gnetales, and angiosperms alone and in combination with other data sets.