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Amber fossil proves Cretaceous beetle ate pollen of flowering plants

This ancient amber trapped both a mid-Cretaceous beetle and the insects' pollen-containing feces, suggesting beetles were providing pollination services about 100 million years ago. Photo by Chenyang Cai, Yanzhe Fu and Yitong Su
This ancient amber trapped both a mid-Cretaceous beetle and the insects' pollen-containing feces, suggesting beetles were providing pollination services about 100 million years ago. Photo by Chenyang Cai, Yanzhe Fu and Yitong Su

April 12 (UPI) -- A newly discovered mid-Cretaceous amber fossil suggests an early beetle species, Pelretes vivificus, visited flowering plants and ate their pollen.

Today, the majority of pollination services for both crops and wild plants are provided by bees and butterflies, but less is known about the identities of the planet's earliest pollinators.

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Previous fossils have shown flies were actively pollinating a diversity of plants some 49 million years ago.

The latest study, published Monday in the journal Nature Plants, suggests beetles were providing pollination services as early as the mid-Cretaceous, nearly 100 million years ago.

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"The beetle is associated with clusters of pollen grains, suggesting that short-winged flower beetles visited angiosperms in the Cretaceous," study co-author Chenyang Cai said in a press release.

"Some aspects of the beetle's anatomy, such as its hairy abdomen, are also adaptations associated with pollination," said Cai, a professor at the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Science.

To understand the origins of pollination and the proliferation of angiosperms, scientists must rely almost entirely on evidence trapped millions of years ago in drops of amber. Plants and tiny insects are usually too small and delicate to be preserved by other means.

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Farmers place sticky traps on trees to monitor insect activity in their fields, but they have a variety of other observational tools at their disposal.

Paleontologists, however, aren't so lucky.

"Imagine if your only insight into an ancient ecosystem were such sticky traps and you were to reconstruct all its ecological interactions based solely on this source of evidence," said lead author Erik Tihelka.

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"That is the challenge faced by paleontologists studying amber," said Tihelka, an entomologist and palaeontologist at the University of Bristol in Britain.

"Luckily, the amber trap from northern Myanmar is one of the richest fossiliferous amber deposits known," Tihelka said. "Besides the unparalleled abundance of fossil insects, the amber dates back to the mid-Cretaceous, right when angiosperms were taking off."

Today, flowering plants account for roughly 80 percent of the planet's vegetation, but during the early Cretaceous, some 125 million years ago, flowering plants were only just beginning to diversify.

Some scientists have suggested angiosperms' rise to dominance was spurred by their early partnership with pollinators.

Evidence of early pollination is scarce, however.

The latest amber fossil suggests the beetle Pelretes vivificus was visiting flowering plants and eating their pollen at least 98 million years ago. Their modern relatives, short-winged flower beetles, continue to visit and pollinate flowers in Australia.

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"The pollen associated with the beetle can be assigned to the fossil genus Tricolpopollenites," said study co-author Liqin Li.

"This group is attributed to the eudicots, a living group of angiosperms, that includes the orders Malpighiales and Ericales," said Li, a fossil pollen specialist at the Nanjing institute.

The new study suggests the diversification of early angiosperms was likely aided by the pollination services of a variety of different insect groups, the researchers said.

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