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Eureka!

The Origin of Flowers

The genome of a rare shrub addresses Darwin’s “abominable mystery”: why flowers suddenly proliferated on Earth millions of years ago

Amborella trichopoda

Amborella trichopoda. Photo: Joel McNeal

“Amborella provides us with a window to the past—a way to study primitive forms of life, and to understand how modern organisms came to be.”
Victor Albert

By Charlotte Hsu

Tulips, with their rubbery petals. Potatoes, which feed much of the world. Oranges, with fragrant fruits born from five-petaled blossoms shaped like stars.

The variety of flowers on Earth is amazingly diverse, but their proliferation remains an enigma—what Charles Darwin, the famed 19th-century naturalist, called an “abominable mystery.”   

It’s one of evolution’s enduring questions: Why did flowers, previously absent from the fossil record, appear to suddenly emerge and explode in number between 145 and 100 million years ago?  

A new study led by UB biologist Victor Albert and researchers at four other universities finds a potential answer in the DNA of Amborella trichopoda, a small tree that grows on the remote Pacific archipelago of New Caledonia.   

With clusters of cream-colored blossoms resembling tiny fireworks, Amborella hails from a venerable evolutionary lineage. Of hundreds of thousands of flowering plants on Earth today, it’s the sole survivor of an ancient branch of flowers that traces its roots to the common ancestor of them all.   

This heritage gives Amborella a special role in scientific study. Like the platypus, a mammal that has stalked the planet for longer than almost any other, Amborella provides us with a window to the past—a way to study primitive forms of life, and to understand how modern organisms came to be.  

After sequencing the species’ DNA, Albert and his colleagues found evidence that the above-mentioned ancestor of all flowering plants underwent what scientists call a “polyploidy event,” a process in which an organism’s entire genome gets duplicated. It happened about 170-200 million years ago, Albert explains, and because redundant copies of genes can evolve to develop new functions, this ancient doubling may have sparked the explosion in plant variety that came soon after.  

This twinning, fantastic as it may seem, happens in animals, too.

“The lineage leading to all vertebrates—including humans—underwent two whole-genome duplications in the ancient past,” Albert says. “In some cases, polyploid individuals can mate with diploids—which, like humans, have two versions of every gene—to produce triploids, which have a third set. North American gray tree frogs are one such example.” 

Further research on Amborella should continue to illuminate the history of flowers. Studies comparing the plant’s genetic material to that of other species could reveal how traits, such as drought resistance and fruit maturation, developed, and how genome-doubling may have encouraged that evolution.

About Amborella

map of New Caledonia

Species name
Amborella trichopoda

Physical appearance
Small understory tree or shrub; flowers are approximately 3-5 millimeters in diameter

Location
Grows in only one place in the world: the largest island of New Caledonia, a South Pacific archipelago located east of Australia

Why it’s special
It’s the sole survivor of an ancient evolutionary lineage that traces back to the last common ancestor of all flowering plants