In a world first, researchers map a 4,200 km transatlantic flight of the painted lady butterfly

In October 2013, Gerard Talavera, a researcher from the Botanical Institute of Barcelona at CSIC, made a surprising discovery of painted lady butterflies on the Atlantic beaches of French Guiana, a species not typically found in South America. This unusual sighting prompted an international investigation into the origin of these butterflies.

Using innovative multidisciplinary tools, the research team led by Gerard Talavera of the Institut Botànic de Barcelona, ​​​​Tomasz Suchan of the W. Szafer Institute of Botany, and Clément Bataille, associate professor in the Department of Earth and Environmental Sciences of the University of Barcelona, ​​Ottawa – with Megan Reich, a postdoctoral researcher in the Department of Biology at uOttawa, Roger Vila and Eric Toro Delgado, scientists from the Institute of Evolutionary Biology, and Naomi Pierce, professor of biology in the Department of Organismic and Evolutionary Biology at Harvard University – embarked on a scientific mission to track the journey and origins of those mysterious Painted Ladies.

The butterflies’ migration was discussed in the article entitled “A trans-oceanic flight of more than 4,200 km by painted lady butterflies”, published in Nature communication on June 25, 2024.

First, the research team reconstructed the wind paths of the period leading up to the arrival of these butterflies in October 2013. They found exceptionally favorable wind conditions that allowed for a transatlantic crossing from West Africa, opening the possibility that these individuals could have flown across the entire ocean to have.

After sequencing the genomes of these individuals and comparing them to populations around the world, researchers found that the butterflies had a closer genetic relationship to African and European populations. This result eliminated the likelihood that these individuals came from North America, strengthening the hypothesis of an oceanic voyage.

Researchers used a unique combination of next-generation molecular techniques. They sequenced the DNA of the pollen grains of these butterflies. They identified two species of plants that grow only in tropical Africa, suggesting that the butterflies took nectar from African flowers before beginning their transatlantic journey.

They analyzed hydrogen and strontium isotopes in the butterflies’ wings, a chemical signal that acts as a ‘fingerprint’ of the area of ​​birth. Combining isotopes with a model of habitat suitability for larval growth revealed a potential birth origin in Western Europe, possibly France, Ireland, the United Kingdom or Portugal.

Dr. Bataille says: “It is the first time that this combination of molecular techniques, including isotope geolocation and pollen metabarcoding, has been tested on migratory insects. The results are promising and transferable to many other migratory insect species. The technique should fundamentally change our understanding of insect migration. ”

‘We usually see butterflies as symbols of the fragility of beauty, but science shows us that they can perform incredible feats. There is still much to discover about their capabilities,” says Roger Vila, researcher at the Institute of Evolutionary Biology (CSIC-Pompeu Fabra University) and co-author of the study.

Strengthened by the wind

The researchers assessed the feasibility of a transatlantic flight by analyzing the energy expenditure for the journey. They predicted that the flight across the ocean, which would take five to eight days without stops, was feasible due to favorable wind conditions.

“The butterflies could only have completed this flight using a strategy that alternated between active flight, which is energetically expensive, and gliding with the wind. We estimate that the butterflies could have flown up to 780 km without wind before using all their energy.” had consumed fat and, therefore, their energy,” says Eric Toro-Delgado, one of the co-authors of the article.

The Saharan air layer is highlighted by researchers as an important air route for dispersal. These wind currents are known to transport large amounts of Saharan dust from Africa to the Americas, fertilizing the Amazon. This study now shows that these air currents can transport living organisms.

The potential impact of migrations in the context of global change

This finding indicates that natural air corridors may exist connecting continents, allowing the spread of species on a much larger scale than previously thought.

“I think this research clearly shows how much we tend to underestimate the dispersal ability of insects. Furthermore, it is entirely possible that we are also underestimating the frequency of these types of dispersal events and their impact on ecosystems,” says Megan. Reich, a postdoctoral researcher at the University of Ottawa who also co-authored the study.

Gerard Talavera, the study’s lead researcher, added: “Throughout history, migration phenomena have been important in defining species distributions as we observe them today.”

Researchers emphasize that due to global warming and changing climate patterns, we may witness more notable changes and a potential increase in long-distance dispersal. This could have a significant impact on biodiversity and ecosystems worldwide.

“It is essential to promote systematic insect distribution monitoring routines, which could help predict and mitigate potential risks to biodiversity from global changes,” concludes Gerard Talavera.