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A 3-D model of the ancestral flower, showing both female (carpels) and male (stamens) parts, and multiple whorls (concentric cycles) of petal-like organs, in sets of threes. Photo: Hervé Sauquet & Jürg Schönenberger

In an ambitious undertaking, an international team of researchers spent six years developing an evolutionary tree of the world’s flowers to reconstruct what the first one may have looked like.

The team, led by Herve Sauquet, from the University of Paris-Sud in France, revealed a 3-D portrait of the flower, which shares some resemblance to the modern water lilly or magnolia. It had both female (carpels) and male (stamens) organs, which were separate from each other. The flower also had many whorls, that were grouped in sets of three.

“In spite of similarities with some extant flowers, there is no living species that shares this exact combination of characters,” the study authors wrote in Nature Communications.

They believe it emerged about 140 million years ago, when the dinosaurs dominated the planet. The oldest fossilized flower yet discovered dates back to 130 million years ago.

To get a better understanding of how the ancestral flower looked, the team essentially worked backwards. They assembled the largest dataset of floral traits ever created, which included samples from 792 different species, spanning 63 orders (98 percent) and 372 families (86 percent) of known flowering plants. They then developed an evolutionary tree that modeled the earliest stages of flower evolution and produced the 3-D rendering showing what traits the first flower would have had.

An intriguing aspect of the ancestral flower is the abundance of whorls it had. Early flowers simplified themselves with fewer whorls, which the researchers credit to boosting pollination efficiency. Flowers evolved rapidly and as a result, pollinating insects also evolved quickly.

Now, flowering plants (also called angiosperms) are the largest group of flowers on Earth – accounting for nine out of every 10 plants in existence. They far outnumber seed plants like conifers, which emerged between 350 and 310 million years ago, and dominated before the presence of angiosperms.

The study authors noted how difficult a task it is to trace an angiosperm’s origin, because the delicate pedals rarely fossilize, leaving a lot of guesswork.

“Estimating features of the ancestral flower is a difficult task, because there are neither suitable outgroups for direct comparison nor fossil flowers known from the time period when this ancestor existed,” the authors note. “In this study, we make these inferences based on the distribution of traits in extant angiosperms and their phylogenetic relationships, and, for the first time, methods using explicit models of stochastic evolution for morphological characters.”

“Although uncertainty remains for some of the characters, our reconstruction allows us to propose a new plausible scenario for the early diversification of flowers, leading to new testable hypotheses for future research on angiosperms.”

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