For Tennesseans, passion flowers are a point of regional pride, officially designated as the state flower of Tennessee in 1919.
Now, a century later, paleontologists have found fossil evidence of an extinct Appalachian passionflower species, Passiflora appalachiana, previously unknown to science.
This ancient species is unique in the Tennessee fossil record, museum officials said, and is proof that these flowers have graced the local landscape for millions of years.
The fossils were found at the Gray Fossil site, supervised by the Don Sundquist Center of Excellence in Paleontology at East Tennessee State University. Located in northeast Tennessee, this site preserves an ancient Early Pliocene ecosystem nearly five million years old, including fossil remains of rhinos, red pandas, alligators, mastodons and more. .
Since the site’s discovery in 2000, researchers have identified several extinct plant species that are new to science, including vines, hickory, winter hazel and now passionflower.
The new species was described by Dr. Elizabeth Hermsen, a researcher at the Paleontological Research Institution in Ithaca, New York, in a recent study published in the International Journal of Plant Sciences, in a special issue celebrating women in paleobotany, the science from fossils to plants.
In the new study, Hermsen identified 13 fossil seeds of the extinct passion flower, each about six millimeters long. These seeds were discovered at the Gray Fossil Site thanks to the dedicated work of site staff and volunteers to separate the tiny fossils from the ancient sediments, museum officials said.
Comparing the structure of these seeds to modern and ancient parents, Hermsen identified them as a type of passion flower. But since they don’t match any known species, she classified them as a new species. These extinct seeds most closely resemble the purple passionflower or maypop, Passiflora incarnata, which lives in Tennessee today.
“The purple passion flower is widespread in the eastern United States today and is somewhat weed,” Hermsen said. “Thus, passionflower seeds from the Gray Fossil site indicate that this more resistant passionflower line was probably established in eastern North America during the Pliocene era.”
Passion flowers are plentiful today, mostly found in the American tropics, but they are rare in the fossil record. These ancient Appalachian passion flowers are the first confirmed record of fossil passion flowers from all of eastern North America. They also provide a rare tropical flavor to the flora of the Gray Fossil Site.
“Many plants at the Gray Fossil site have northern hemisphere distributions in the fossil record, occurring in North America, Europe and Asia. Plus, they often live in North America and East Asia today, ”Hermsen said. “Passion flowers are currently the most diverse in South America, with very few species native to eastern North America and eastern Asia, and the seeds from the Gray Fossil site do not appear to have relation with the Asian passion flowers. “
Hermsen suspects that these ancient passion flowers may have spread to North America from ancestors in warmer southern regions, an unusual scenario for plants at the Gray fossil site. This new species expands scientists’ understanding of the complicated ways in which ecosystems have reshaped and reorganized over the past millions of years.
Over 100 different plant types have been identified from fossil seeds and pollen at the Gray Fossil site, although many are still awaiting detailed study. Hermsen is currently engaged in researching more of these plants, and she suspects there are more new species to be discovered.
“Honestly,” she said, “I wish I had more time to work on all the flora.