The unlikely event of a butterfly crossing the Atlantic Ocean

You have probably seen this migrant somewhere insectis one of the most common butterflies around the world.

‘Vanessa cardui’, distinguished by its brown and orange patterns on its wings, lives on all continents except Antarctica and South America.

That’s why Gerard Talavera, an entomologist at the Institute of Botany in Barcelona, ​​was surprised to see a group of V. cardui butterflies on the Atlantic coast of French Guiana.

How did butterflies come to South America? Did they come from the north? Or maybe from the other side of the Atlantic? The entomologist was determined to find out.

And his team is now reporting in the review Nature Connections the only explanation is that the insect completed a transatlantic journey of 4,200 km, the first transoceanic journey on record for any lepidopteran species.

Fair wind

First, the researchers looked at wind patterns prior to the butterflies’ arrival in October 2013. And indeed the wind was favorable for the flight from West Africa.

Butterflies are more likely to be carried by the wind when they begin their annual migratory journey from Africa to Europe.

Later, the butterflies found in Guyana were subjected to genetic analysis, which showed that the insects were not more closely related to African and European populations than to North American populations.

This was followed by genetic testing of the pollen grains found in the butterflies, which identified two African plants – an indication that the insects had eaten in Africa before crossing the Atlantic.

And the suspicions were confirmed by isotopic analyzes of the butterflies’ wings, which showed that the colorful insects came from Western Europe, possibly France, Ireland, England or Portugal.

It is likely that the butterflies were taken when they began their annual migration journey from Africa to Europe.

In any case, this is the first time that these new laboratory techniques have been applied to migratory insects. “The results are promising and the same techniques can be applied to many other species. They could fundamentally change what we know about migratory insects,” said Clement Bataille of the University of Ottawa in Canada, a member of the research team.

Energy costs

The study also looks at the energy costs required for the journey and estimates that the transatlantic flight, which is estimated to last 5-8 days non-stop, is only possible thanks to strong winds.

“Butterflies could complete the journey using a strategy of switching between powered active flight and passive gliding. We estimate that without the wind, they could fly a maximum of 780 kilometers, so that they could use up their fat reserves and therefore energy,” said Eric Toro-Delgado of the Institute of Botany in Barcelona.

The same westerly winds are also known to carry large amounts of dust from the Sahara, which acts as fertilizer for the Amazon rainforest.

Gerard Talavera, the researcher who identified Vanessa Cardo in South America, noted that as climate change alters environmental conditions, migration will become increasingly important for the insect’s survival.

As he says, “It is critical that we develop ways to monitor insect dispersal that will help predict and address potential threats to biodiversity from climate change.

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