A new study found that the world’s first flower had both male and female reproductive parts. A group of researchers virtually reconstructed the last common ancestor of all living flowers, which sprouted across the world about 140 million years ago.

Angiosperms, or flowering plants, make up about 90 percent of all living land plants and scientists believe there are more than 300,000 different species in the world.

A model of the reconstructed flower. It has both female and male parts. Image Credit: Hervé Sauquet and Jürg Schönenberger
A model of the reconstructed flower. It has both female and male parts. Image Credit: Hervé Sauquet and Jürg Schönenberger

However, while angiosperms are believed to have sprouted between 140 million and 250 million years ago, there are no fossil flowers dated farther back than 130 million years ago, so a team of researchers decided to reconstruct the ancestor of angiosperms. Their findings were published online Tuesday in the journal Nature Communications.

Bisexual flowering plant ancestor had its petals arranged in sets of three

The reconstruction conducted by the researchers at the University of Paris-Sud in France showed how the ancestor flower of angiosperm differed from its modern descendants.

“The petal-like parts and the stamens [male reproductive organs in a flower] were more numerous than in most living species, and were probably organized in multiple sets of three,” Hervé Sauquet, study’s lead author and associate professor at the Laboratory of Ecology, Systematics, and Evolution at the University of Paris-Sud, told Live Science.

Sauquet, an evolutionary biologist, said that we almost know nothing about how flowers have evolved since their origins, even while it’s important to know this for their ecological role on Earth. Notable evolutionary scientist Charles Darwin was also puzzled about the origin of modern flowers and once described their diversification as an “abominable mystery.”

While researchers knew a lot about the evolutionary history of angiosperms, especially how plant families are related to one another, they knew very little about how their emblematic structure (the flower) has evolved and diversified since its origin, Sauquet told Live Science.

“That’s why I decided to join forces with other experts and create the international eFLOWER initiative to tackle these questions,” he said.

Since there are no known fossils of the world’s oldest flowering plant, the researchers used a method known as ancestral state reconstruction.

Researchers used several methods to reconstruct ancient angiosperm

Sauquet and his colleagues constructed a family tree of angiosperms based on genetic data from 792 species. The method used information from the known evolutionary tree –a diagram that shows relationships between flowers based on their differences and similarities- as well from the known characteristics of modern flowers, to guess the structure of the first flowers at different points of divergence in the family tree.

The researchers also created probabilistic models that calculated the likelihood of the emergence of some floral characteristics over time to infer the ancient flower’s anatomy. Sauquet noted that method allowed them to find out what ancestral flowers like and helped them to measure uncertainty.

The direct descendants of the world's first flower. Image Credit: Hervé Sauquet and Jürg Schönenberger
The direct descendants of the world’s first flower. Image Credit: Hervé Sauquet and Jürg Schönenberger

The process was repeated several times using family trees produced using all the methods to check whether the results were the same. The final result showed that the ancestor of flowering plants was a delicate flower with rings of upturned petals arranged in threes.

“This is what we infer to be the ancestral flower of all living flowering plants,” Sauquet told The Guardian.

The ancient flower had three or four whorls for each organ

When flowers first sprouted on Earth, they went through a series of simplification processes in which their structures were either reduced or merged until the flowers finally settled on a stable and optimal architecture, said Sauquet. Then, after the flowers settled and achieved this stable structure, they likely began to diversify and develop other features like symmetry, according to him.

Beverly Glover, a professor of plant systematics and evolution at the University of Cambridge stated that the finding was “exciting,” as there is a species alive currently that comes from an early ramification of the angiosperm family tree. Such species, known as Amborella, has separate male and female flowers, unlike its ancestor.

The study also found that the ancestral flower’s stamens were not arranged in spirals but rather in concentric circles known as whorls, with only three petals or sepals in each. Regarding that, Sauquet noted he believes many people are not going to believe them because the finding overturns a long idea that those structures in ancient flowers had a spiral arrangement that led to the whorled structure that is prevalent today.

The reconstruction also suggested the ancestral flower had three or four whorls for each organ, even though most modern flowers have fewer. He explained that since only one whorl of sepals for protection and one whorl of petals to attract pollinators are needed for a functional flower, having more could have been a waste of resources for modern flowers.

Source: Live Science