Conflicting Phylogenetic Hypotheses involving the seed plants. Morphological evidence (synapomophic characterstics shared between angiosperms and Gnetales) have shaped the anthophyte theory, where these two taxa form sister groups (Panel A; [1, 2, 5]). In contrast, most molecular studies postulate gymnosperms as a monophyletic group sister to all angiosperms, and place the Gnetales as a sister group to the conifers (Panels B and D; [7–9, 15, 16]). Adding to the controversy, a recent study involving phytochrome genes (; Panel D) has placed the Gnetales as basal gymnosperms, with Ginkgo and cycads as sister taxa branching after the Coniferales.
de la Torre et al. BMC Evolutionary Biology 2006 6:48 doi:10.1186/1471-2148-6-48