New fossil pushes physical evidence for insect pollination to 99 million years: News at IU: Indiana University

BLOOMINGTON, Ind. — A new study co-led by researchers in the United States and China has pushed back the earliest known physical evidence of insect pollination of flowers to 99 million years ago, during the mid-Cretaceous.

The revelation is based on a flower beetle with pollen on its legs discovered preserved in amber deep in a mine in northern Myanmar. The fossil comes from the same amber deposit as the first ammonite discovered in amber, which was reported by the same research group earlier this year.

The newly reported fossil is described Nov. 11 in the journal Proceedings of the National Academy of Sciences. The fossil, which contains both the beetle and the pollen grains, pushes the first documented example of insect pollination back to a time when pterodactyls still roamed the skies – about 50 million years earlier than previously thought. thought so before.

The US co-author of the study is David Dilcher, a professor emeritus in the Department of Earth and Atmospheric Sciences at IU Bloomington College of Arts and Sciences and a researcher affiliated with the Indiana Geological and Water Survey. As a paleobotanist studying the first flowering plants on Earth, Dilcher conducted research on the fossilization process of amber.

The study’s co-lead author is Bo Wang, an amber fossil expert at the Nanjing Institute of Geology and Paleontology, where the specimen was purchased and analyzed.

According to Dilcher, who provided a morphological examination of the 62 pollen grains in amber, the shape and structure of the pollen show that it evolved to spread through contact with insects. These characteristics include pollen size, “ornamentation” and clumping ability.

The grains also likely come from a flower species in the eudicot group, one of the most common types of flowering plant species, he said.

Pollen was not easy to find. The powdery substance was revealed hidden in the insect’s body hair under confocal laser microscopy. The analysis took advantage of the fact that pollen grains glow under fluorescent light, contrasting sharply with the darkness of the insect’s shell.

The insect in the amber is a recently discovered species of beetle, which the study authors named Angimordella burmitina. Its role as a pollinator has been determined based on several specialized physical structures, including body shape and pollen-feeding mouthparts. These structures were revealed by an imaging method called X-ray microcomputer tomography, or micro-CT.

“It’s extremely rare to find a specimen where the insect and the pollen are preserved in a single fossil,” Dilcher said. “Besides the importance as the earliest known direct evidence of insect pollination of flowering plants, this specimen perfectly illustrates the cooperative evolution of plants and animals during this period, during which a true exhibit of flowering plants has occurred.”

Prior to this study, the earliest physical evidence for insect pollination of flowering plants came from the Middle Eocene. The age of the new fossil was determined based on the age of other known fossils in the same location as the discovery of the fossilized beetle.

The other study authors were Tong Bao and Jianguo Li from the Nanjing Institute of Geology and Paleontology. Bao is also affiliated with the Institute of Geosciences and Meteorology at the University of Bonn in Germany.

This work was supported in part by the Chinese Academy of Sciences and the National Natural Science Foundation of China.

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