This Is What Earth’s Earliest Flowers Might Have Looked Like

An international team of researchers at the eFLOWER project has reconstructed what the Earth’s ancestral angiosperm flowers might have looked like.

3D model of the ancestral flower reconstructed by the eFLOWER team. Image credit: Sauquet et al, doi: 10.1038/ncomms16047.

Flowering plants (angiosperms), with at least 300,000 species, are by far the most diverse group of plants on our planet. They include almost all the species used by people for food, medicine, and many other purposes.

However, flowering plants arose only about 140 million years ago, quite late in the evolution of plants, toward the end of the age of the dinosaurs.

Since then they have diversified spectacularly. However, no one knows exactly how this happened.

The origin and early evolution of flowering plants — especially flowers still remain one of the biggest enigmas in biology.

“Previous attempts to reconstruct the ancestral flower using a modern phylogenetic framework of angiosperms have improved our understanding of ancestral floral traits, such as the ancestral structure of the carpel,” the scientists said.

“However, several essential aspects of the ancestral flower have so far remained unresolved, due to particularly confounding variation in floral structure among the earliest diverging lineages of angiosperms. For instance, it was still unknown whether the ancestral flower was unisexual or bisexual.”

According to the eFLOWER team, the ancestral flower was bisexual, with both female (carpels) and male (stamens) parts, and with multiple whorls (concentric cycles) of petal-like organs, in sets of threes.

About 20% of extant flowers have such ‘trimerous’ whorls, but typically fewer: lilies have two, magnolias have three.

Ancestral state reconstruction of functional sex of flowers in angiosperms: the study results show that bisexual flowers are ancestral and that unisexual flowers evolved many times independently; the pie charts at the center of the figure indicate the proportional likelihoods for reconstructed ancestral states at 15 key nodes. Image credit: Sauquet et al, doi: 10.1038/ncomms16047.

“When we finally got the full results, I was quite startled until I realized that they actually made good sense. No one has really been thinking about the early evolution of flowers in this way, yet so much is easily explained by the new scenario that emerges from our models,” said co-lead author Dr. Hervé Sauquet, from the Université Paris-Sud in France.

“These results call into question much of what has been thought and taught previously about floral evolution,” added co-lead author Professor Juerg Schoenenberger, from the University of Vienna in Austria.

The team also reconstructed what flowers looked like at all the key divergences in the flowering plant evolutionary tree, including the early evolution of the two largest groups of flowering plants: monocots (e.g., orchids, lilies, and grasses) and eudicots (e.g., poppies, roses, and sunflowers).

“The results are really exciting,” said co-author Dr. Maria von Balthazar, a senior scientist at the University of Vienna.

“This is the first time that we have a clear vision for the early evolution of flowers across all angiosperms.”

The research appears this week in the journal Nature Communications.

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Hervé Sauquet et al. 2017. The ancestral flower of angiosperms and its early diversification. Nature Communications 8, article number: 16047; doi: 10.1038/ncomms16047