Early detection of fossil insect pollination

The 99 million-year-old beetle fossils excavated in Myanmar are the earliest evidence of insect pollination.

Insect fossils and pollen are well preserved inside amber. Photo: Phys.

American and Chinese scientists have found a 99 million-year-old piece of amber containing fossils of a beetle and dozens of pollen grains inside a mine in northern Myanmar. The discovery pushed back the first case of pollination thanks to insects returning to the middle of the Cretaceous, 50 million years earlier than previously noted.

The two lead authors of the study, including Honorary Professor David Dilcher from Bloomington University of Science and Arts (USA) and fossils expert Bo Wang from Nanjing Institute of Geology and Archeology (China), observed amber under a laser scanning confocal microscope and found a total of 62 pollen grains clinging to insects' feathers.

Detailed analysis of the morphology of pollen showed that they evolved to be easily dispersed when exposed to insects. These characteristics include the size, shape, structure and clotting ability of the pollen. They may be derived from a flower in the true group of dicotyledonous plants (Eudicots).

A. burmitina beetles suck honey and Eudicots pollen. Graphic: Ding-hau Yang.

The fossil insect inside amber has been identified as an angimordella burmitina beetle. Based on an X-ray image of a micro-CT (micro-CT), the team found that it had the physical characteristics unique to a pollinator, including the body shape and the structure of a pollen-eating mouth. .

Images of insects and pollen under a microscope. Photo: Phys.

"It's very rare to find such a specimen containing both insect preserved pollen and pollen," Dilcher stressed. "In addition to being the earliest evidence of insect pollination, this finding perfectly illustrates the collaborative relationship between animals and plants in the Cretaceous period."

The fossil report was published in the November 11 issue of Proceedings of the National Academy of Sciences.