The Mostly Male Theory of Flower Evolutionary Origins: From Genes to Fossils

TLDR

Recent theories of flowering plant origins, the Anthophyte and Neo‑Pseudanthial models, rely on morphological phylogenies that place Gnetales as either sister to or paraphyletic relative to angiosperms, making Gnetales central to homology assessments. Our analyses show that gymnosperms are monophyletic with Gnetales clustering with other gymnosperms, invalidating the Anthophyte and Neo‑Pseudanthial models and supporting earlier seed‑fern hypotheses, while homeotic gene data suggest flowering plants lost one of two ancestral Floricaula/LEAFY copies, pointing to a new developmental framework for flower organization.

Abstract

Abstract The two recent theories of flowering plant evolutionary origins—the Anthophyte and Neo-Pseudanthial theories—are based on phylogenies (from morphological data) that show Gnetales as extant sister to angiosperms or as paraphyletic to angiosperms. Gnetales figured prominently in homology assessments and evolutionary scenarios of these theories. Several recent studies, including ours, provide strong evidence that extant gymnosperms are monophyletic, so Gnetales are most closely related to other gymnosperms, not to flowering plants. This removes the basis for both recent theories, leaving earlier theories that relate flowering plants to fossil “seed-fern” gymnosperms as the only active contenders. Our data from the homeotic gene Floricaula/LEAFY imply that the lineage leading to flowering plants originally had two copies of this gene, but that one copy was lost in flowering plants, which suggests a new theory: that developmental control of flower organization derives more from systems active in the m...