XVI International Botanical Congess

Gymnosperm monophyly is strongly supported by the Floricaula/LEAFY (LFY) gene tree, as discussed in our other poster. This refutes the Anthophyte theory of flower origins, which is based on Gnetales being extant sister to angiosperms. The homeotic gene LFY generally helps specify flowering plant apices as reproductive, rather than vegetative, by stimulating expression of a cascade of downstream genes. In gymnosperms the Needle paralog (of LFY) seems to help specify female reproductive structures, while the Leaf paralog specifies male structures. Angiosperms appear to have lost the ancestral Needle paralog, while retaining the Leaf paralog, so angiosperms are likely to have retained more of the gene cascade active in male rather than female structures of the gymnosperm ancestor. Our theory is consistent with diverse observations and makes testable predictions.