Through the Fossil Grapevine: Museum Scientist Helps Untangle How the Fruit Thrived in the Aftermath of Extinction

The batch of newly-described fossils includes a species named after Smithsonian botanist Jun Wen

July 23, 2024

Grapes and their relatives originated in dense forests, like this lowland tropical forest in central Panama, more than 60 million years ago. STRI Archives

Today, few fruits are easier to find than grapes. There are nearly one thousand species of grapes and their vine-growing relatives in the plant family Vitaceae. These include the species that produce the succulent bunches of berries that humans enjoy by the handful or glass.

Finding fossils of this far-reaching fruit is another story. The squishy part of grape fruits doesn’t fossilize well. Instead, paleobotanists rely on fossilized grape seeds. While these fossil seeds routinely turn up in certain areas, like the United States, there are other regions where they are seldom found or unknown entirely. This includes the tropics of Central and South America, an area that is seemingly perfect for this largely tropical group of plants.

A new batch of fossilized seeds is poised to help fill this geographic gap. In a paper published this month in the journal Nature Plants, a team of researchers document nine species of prehistoric grapes, including four new to science, from sites in Colombia, Panama and Peru. One of these species is 60 million years old, making it the earliest grape relative known from the Western Hemisphere.

None — The fossil seed *Lithouva susmanii* represents the earliest known species of grape relative in the Western Hemisphere. Seen here is the original fossil (top left), a CT scan (top right) and an artist reconstruction of both sides of the seed. Photo and CT Scan by Fabiany Herrera, reconstruction by Pollyanna von Knorring

“It was understood right away that these fossil seeds were significant because there hadn't been any good fossil evidence of the grape family in the neotropics,” said Gregory Stull, a botanist at the National Museum of Natural History and one of the authors on the new paper.

Stull, who is affiliated with the United States Department of Agriculture, studies the evolution of flowering plants. He teamed up with several researchers on the new study, including Fabiany Herrera, a paleobotanist at the Field Museum in Chicago, and Mónica Carvalho, a curator at the University of Michigan’s Museum of Paleontology. Herrera and Carvalho’s field work uncovered the fossil seeds analyzed in the new paper.

The various seeds range in age from 60 to 19 million years old. The oldest species of the bunch, Lithouva susmanii, cropped up in Colombia just a few million years after the Cretaceous–Paleogene extinction event, when an asteroid impact sent Earth’s climate into disarray. The cataclysmic collision is infamous for dooming the non-avian dinosaurs. But it also had an outsized impact on plant communities around the world, wiping out more than half of all plant species at the time.

But it was not all doom and gloom for flora. The extinction event opened up space for a multitude of new flowering plants to bloom. And without behemoths like dinosaurs uprooting trees and vacuuming up foliage, overgrown forests took root. “With dinosaurs gone, the forests are able to become denser, which makes being a vine more important,” Stull said. Vine-producing plants like grapes could rise above the crowded understory and climb towards the sunlight poking through the canopy.

Grapes and their relatives appeared in the immediate aftermath of the extinction event. The oldest grape seed fossils, which were found in India, are roughly 66 million years old. However, other fossil seeds from this timeframe are rare, especially in Central and South America. This is puzzling, because these tropical regions would have provided prime habitats for early grapes and their relatives. The newly described fossil seeds offer the best evidence yet that these plants were components of Central and South American ecosystems throughout the Cenozoic, the geologic era that began after the extinction event.

While the fossils themselves are tiny, it was not difficult to determine that they belonged to ancient relatives of grapes. Plants in the Vitaceae family produce very distinctive seeds that have a pair of parallel grooves running alongside one side of the seed called ventral infolds; on the other side of the seed is a distinctive ridge-like structure called a chalazal knot. “There's not much you can confuse grape seeds with,” Stull said. The size and shape of these features vary from species to species, which helps researchers match specific seeds to particular species or genera in the family.

The new species of prehistoric Vitaceae plants allow the team to restructure the evolutionary grapevine. In addition to being the oldest, Lithouva susmanii is also notable as a close relative of the living group that includes the common grape vine, Vitis. According to Stull and his colleagues, the L. susmanii fossils reveal that this group probably originated in the Neotropics, a region once devoid of known grape fossils.

The researchers named another new species, Ampelocissus wenae, in honor of Smithsonian botanist Jun Wen. “Jun is one of, if not the world experts on the grape family,” Stull said of his colleague. “She's traveled all over the world collecting species and creating the framework for what we know about the evolution of the grape family.” Wen’s namesake grape lived around 19 million years ago in the area that now borders the Panama Canal. Its rounded seed had a pair of large grooves, giving it the appearance of a wide-eyed owl.

Discovering these fossil seeds not only sheds light on where early grapes lived in the past. It also may provide clues on where these plants might reside in the future. “The seeds provide evidence that a group of plants was in a certain place at a certain time, allowing us to track grapes through space and time,” Stull said. “This allows us to see which regions they favored in the past and what climates they may favor in the future.”

Jack Tamisiea | | READ MORE

Jack Tamisiea is a Science Communications Specialist at the Smithsonian's National Museum of Natural History. In addition to covering all things natural history for the museum's blog, Smithsonian Voices, he tracks media coverage and coordinates filming activities for the museum's Office of Communications and Public Affairs. Jack recently completed his masters in science writing at Johns Hopkins University and his writing has appeared in the New York Times, Scientific American, National Geographic and other science-focused publications. In his free time, he loves exploring the outdoors with a sketchbook and camera. You can read more of Jack's work at https://jacktamisiea.com.