A Prehistoric Beetle May Provide New Evidence of Ancient Pollinators

Researchers found a Cretaceous-era beetle trapped in amber alongside pollen, strengthening the argument that ancient insects may be responsible for the rise in flowering plant life.

Ecological reconstruction of Pelretes vivificus vesting angiosperm flowers in the Burmese amber forest (~99 Ma). (Credit: Jie Sun)

(CN) — Scientists recently uncovered the amber-trapped remains of a beetle from the Cretaceous period — which they believe to be among the earliest known pollinators on Earth.

Two hundred million years ago, the planet was still quite green but there were no flowers in sight. That has left many researchers wondering how the symbiotic relationship between flowering plants and pollinators began. What came first, the flower or the bee (or in this case, beetle)?

Flowering plants, also known as angiosperms, first began to thrive about 125 million years ago — today they make up over 80% of the plant life on Earth. Scientists believe their rise coincided with that of pollinating insects, but evidence in the fossil record has thus far been scarce. Beetles have often been proposed as a likely candidate because of their long evolutionary history, and many scientists believe they played a key role in the diversification of both groups.

A team of researchers from The University of Bristol in the U.K. and the Nanjing Institute of Geology and Paleontology in China unearthed the remains of this prehistoric beetle in Myanmar. They describe the discovery in a new study published Monday in the journal Nature Plants, having found its fossilized feces to be composed entirely of pollen.

“Our fossil short-winged flower beetle provides the first truly direct evidence of pollen feeding in Cretaceous beetles, in the sense that the gut content is preserved alongside the fossil itself,” explained Erik Tihelka, an entomologist and paleontologist at the School of Earth Sciences in Bristol, in an email. “The coprolites (fossil fecal pellets) of the beetle are composed almost entirely of eudicot pollen. In paleontology, it is rarely possible to link an extinct animal to its diet with such a degree of certainty.”

Tihelka said the team’s findings demonstrate a direct link between early flowering plants in the Cretaceous period and pollinating insects of the era, proving a biological link between the two rather than a passing association. Previous work found an indirect relationship between early pollinators and angiosperms, but this is among the first examples of direct evidence linking the two, and the earliest known example involving a species of beetle.

Rather than merely being trapped together in the same bit of gooey amber, this new specimen proves the short-winged flower beetle was actually eating pollen, a lot of pollen, and wasn’t simple entombed alongside it. Amber is tree resin that has been fossilized, and thanks to amber scientists can see and study prehistoric insects and plant matter frozen in time exactly as they were, providing a vital glimpse into the past.

“Farmers who want to protect their orchards can set up sticky traps on trees to monitor insects,” Tihelka explained in a related statement.  “Now 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. That is the challenge faced by paleontologists studying amber. Luckily, the amber trap from northern Myanmar is one of the richest fossiliferous amber deposits known. Besides the unparalleled abundance of fossil insects, the amber dates back to the mid-Cretaceous, right when angiosperms were taking off.”

The fossil came from a mine in the Hukawng Valley, Kachin State, in Northern Myanmar. The authors dated it back nearly 100 million years to the Burmese rainforest, providing the earliest known evidence of pollinating beetles.

They explained that beetles are unique among pollinators in that they consume pollen whole, and thus dozens of pollen grains can be found in their fecal pellets, allowing researchers to make a direct connection between the two. They concluded that the beetle’s fecal pellets are composed of the same type of pollen that was found surrounding and attached to the beetle, further strengthening their association.

“Other fossil beetles entombed in amber alongside pollen grains have been discovered in the past, but now we have unequivocal evidence of their diet and know that they weren’t just coincidentally co-preserved together,” Tihelka said in the email. “Perhaps most importantly, this unusual finding tells us that by some 99 million years ago, beetles were already among the first visitors of flowering plants. This was long before other groups such as bees and pollinating butterflies came along.”

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