An oil rig cast 130 miles off the north-east coast of Scotland is probably one of the last places you would expect to find insects. But that’s exactly where a hardy group of hoverflies has been discovered, hunkering down on their long migration across the North Sea.
Perhaps more surprising still is that most of these insects were found to be carrying pollen grains, despite there being no plants on the rig and no land nearby.
According to researchers from the University of Exeter, who conducted a study on the small marmalade hoverflies, the discovery suggests the animals are capable of transporting pollen hundreds of miles, potentially linking plant populations – from both natural ecosystems and farmland – across Europe.
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To find out more about this extraordinary behaviour, researchers studied 121 of the tiny migratory hoverflies from an oil rig in the Britannia oil and gas field north-east of Aberdeen in Scotland.
The team found that 92% of the insects carried pollen, which comprised up to 14 different plant species. These included common wild plants such as nettle, black elder and meadowsweet, but also a range of agricultural crops, including vegetables, cereals, legumes, nuts and fruits.
“By analysing the pollen samples and wind patterns, we estimate that many of the hoverflies had flown from places including the Netherlands, northern Germany and Denmark – over 500km away,” says Toby Doyle, from the Centre for Ecology and Conservation at Exeter’s Penryn Campus in Cornwall.
The researchers highlight not just the hoverflies’ contribution to pollination, but also their role in supporting farming. “By flying all over Europe – from northern islands and Norway to Spain and Portugal – these migratory hoverflies are probably providing a range of vital benefits both to humans and to plant biodiversity,” says Dr Eva Jimenez-Guri, also from the Centre for Ecology and Conservation.
“As well as being beneficial pollinators, marmalade hoverflies are also natural pest controllers – eating prey including aphids, helping to reduce crop damage,” adds Jimenez-Guri.
The study found that hoverflies reached the oil rig in both June and July. The timing suggests that some were travelling north and others south, depending on seasonal migrations.
To make these journeys, the insects rely on favourable winds, often waiting before launching themselves in the right direction. Researchers believe the hoverflies landed on the rig either to rest or to search for food during their migration.
“The results highlight the important role of migratory hoverflies in long-distance gene flow,” says researcher Dr Karl Wotton. “The next stages of investigation should look at the ecological and agricultural implications of this phenomenon at the continental scales at which these species move.”
Top image: Britannia platform in the North Sea. Credit: Craig Hannah
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