Scientists analyzed insect feeding damage to thousands of leaf fossils from Patagonia, Argentina, over the Cretaceous-Paleogene boundary, and found evidence that ecosystems there recovered twice as fast as in the United States.
Insect feeding damage on a fossil leaf, including holes and a leaf mine (bottom right), made by a larval insect that fed on tissue within the leaf. The fossil is 67-66 million years old and from the Lefipán Formation in Patagonia, Argentina.
Donovan and his international team found leaf-mining insects completely disappeared in Patagonia during the extinction event, as previous studies show happened in the U.S. But unlike the U.S., where it took 9 million years to return to pre-impact insect diversity, recovery happened in just 4 million years in Patagonia.
“Insects and plants are the most diverse multicellular organisms in the world, and they are known to respond to major environmental changes,” Donovan said. “So they make a great resource to study our past.”
The team analyzed 3,646 fossils from Patagonia searching for signs of leaf miners — insect larvae named for the type of damage they cause tunneling though leaves for food. These feeding paths, and the insects’ droppings, both create distinctive patterns and can be compared among fossils at different sites.
“Michael developed this technique of very detailed examination of leaf miners, and new methods for looking at the critical differences among these feeding trails in fossil leaves,” said Peter Wilf, professor of geosciences, Penn State and paper co-author. “He’s teased apart this huge story from the tiny differences in how baby insects did their business in leaves that lived 66 million years ago.”
“There was no evidence of survival, which is similar to what I found when working on my master’s research at the Mexican Hat site in Montana,” Donovan said. “But what we do find in Patagonia is a pretty diverse group of novel leaf miners that appear much sooner than in the western U.S.”
View of the Palacio de los Loros 2 fossil plant locality in Chubut, Patagonia, Argentina. The locality was deposited in the early Paleocene around 64 million years ago.
“The richness of plant-insect associations that we observed during the recovery may be a contributing factor to insect biodiversity in modern South America,” Donovan said. “We can look far into the past and see these patterns that influence life on Earth as it is today.”
Wilf said the study, the first of its kind outside the western U.S., can help scientists answer questions about modern global biodiversity.
Insect damage, including multiple small leaf mines (upper right) and margin feeding (upper left), on a fossil leaf from an early Paleocene fossil plant locality, Las Flores (62.52–62.22 Ma), in Patagonia, Argentina.
Other researchers on this project were Ari Iglesias, Universidad Nacional del Comahue, Argentina; Conrad C. Labandeira, National Museum of Natural History, the Smithsonian Institution; and N. Ruben Cuneo, Museo Paleontologico Egidio Feruglio, Trelew, Argentina.
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