Scientists discover fossils of oldest known potential pollinators

Nearly 200m years before the mosquito in Jurassic Park became trapped in amber, hundreds of ancient insects were encased in sediment along the bank of the Sylva river that flows through the Urals.

Now, scientists inspecting the flattened creatures have found a handful that appear to mark a moment in history: they are the oldest known insects to be covered in pollen, and perhaps some of the world’s first plant pollinators.

Rare fossils of the earwig-like insects were discovered when palaeontologists cracked open rocks along the riverbank near the half-derelict village of Chekarda in Russia. At 280m years old, the specimens predate what were previously the earliest known pollen-covered insects by about 120m years.

Known as tillyardembiids, the fossilised insects had clumps of pollen on their heads, bodies and legs, which under a fluorescent microscope looked like Christmas baubles. The pollen was found to come from a narrow range of seed-producing, non-flowering plants called gymnosperms. Flowering plants evolved 250m to 150m years ago, but became far more common 100m years ago as the rise in pollinators helped transform the diversity of terrestrial life on Earth.

Writing in Biology Letters, the team from Russia and Poland concede it is impossible to know whether their ancient insects contributed to pollination in the Permian period, but suggest that by eating pollen – and covering themselves in the grains – the creatures were an “evolutionary precursor” to the mutually-beneficial arrangement.

“It was like touching the past,” said Alexander Khramov, a senior researcher at the Paleontological Institute, Russian Academy of Science in Moscow, on seeing the fossils. “This discovery sheds light on the early evolution of insect pollination. It provides direct, smoking-gun evidence of pollen dispersion by Paleozoic insects. And we could say that tillyardembiids were picky eaters, specialised on a rather narrow range of host plants.”

The Permian period covers the last 47m years of the Palaeozoic era, which spans 540m to 250m years ago. Many insects preserved in amber date to 100m years ago.

Tillyardembiids had wings and so were potentially highly effective at dispersing pollen, but whether the insects co-evolved with gymnosperms as the plants’ pollinators is likely to remain a mystery.

“We cannot go back in a time machine to observe whether these insects did pollination work or not. Even if they pollinated ancient gymnosperms all day round, there are no ways to prove it with certainty by means of palaeontology,” Khramov said.

“Who knows, maybe they simply gobbled up pollen, and plants did not benefit from it? Anyway, what we could say for sure is that tillyardembiids visited quite a narrow range of plants and carried their pollen in large amounts. So I do not see why they could not have been pollinators,” he added.

Charles Wellman, professor of palaeobiology at the University of Sheffield, said the majority of modern plants are insect pollinated. “How and when insect pollination began is a compelling question. This new fossil discovery suggests that insects had begun to steal plant pollen to eat millions of years before the process of pollination evolved. However, this eventually became an association of mutual benefit, as plants developed mechanisms to ensure that the thieves left with pollen attached, that fertilised neighbouring plants as they fed on them.”

Barry Lomax, professor of plant palaeobiology a the University of Nottingham, said plant-insect interactions define the modern world, with pollinator services proving the backbone for much of our food production. The study, he said, provided evidence for the antiquity of the relationship, one that became established well before the evolution of flowers which likely occurred in the Cretaceous period about 135m years ago.

“By examining the type of pollen, the authors showed that it comes from just a handful of plant species, suggesting close association between the plants and these insects,” Lomax said.

“The exciting thing about this discovery is the fact that there appears to be a degree of specialisation in plant-insect interactions and that this specialisation predates flowering plants and it suggests the possibility that insect pollination predates flowers.”