An international team led by the Higher Council for Scientific Research (CSIC), an institution dependent on the Ministry of Science, Innovation and Universities, documented a transoceanic flight of over 4,200 km by Painted Lady (Vanessa cardui), which is a record for an insect. The study, published in the journal Nature Communications, documents a journey that lasted between five and eight days, made energetically possible with the help of the trade winds.
Researchers from the Botanical Institute of Barcelona (IBB), a joint center of the CSIC and the Barcelona Museum of Natural Sciences Consortium, as well as the W. Szafer Botanical Institute (Poland), the University of Ottawa (Canada), the Institute of Evolutionary Biology (IBE, CSIC -Pompeu Fabra University) and Harvard University (USA) participate in the study.
Record flight for a small insect
In October 2013, the researcher of the Botanical Institute of Barcelona of the CSIC, Gerard Talavera, identified several Chardon Moths on the Atlantic beaches of French Guiana. These sightings were completely unusual, as this species does not occur in South America. Where did they come from?
New techniques to solve the riddle
A multidisciplinary approach has made it possible to decipher the route and origin of these butterflies. The two initial hypotheses were that they could have originated from North America, where the closest populations are found, from Africa or from Europe. By analyzing the wind trajectories, the researchers observed a sustained direction from West Africa, opening the possibility of an Atlantic crossing.
By studying the genetic diversity of butterflies, which required the collection of samples of populations from all continents, The researchers determined that the specimens observed in South America were related to populations from Europe and Africa, which rules out the possibility of a North American origin. The researchers also analyzed the DNA of the pollen the butterflies carried on their bodies and identified two plant species found only in tropical Africa, which proves that butterflies visit the flowers of this region.
Finally, the team analyzed stable isotopes of hydrogen and strontium from butterfly wings. The wings retain isotopic signals specific to where they were reared during their larval phase, allowing their natal origin to be inferred. Thanks to this data, they determined that their origin was most likely in Western European countries such as France, Ireland, the United Kingdom and Portugal.
“The Thistle Moths arrived in South America from western Africa, flying at least 4,200 km across the Atlantic. But their journey could have been even longer, starting in Europe and crossing three continents, representing a migration of 7,000 km or more. This is an extraordinary feat for such a small insect,” explains Clément Bataille, professor at the University of Ottawa in Canada and co-author of the article.
“We tend to think of butterflies as a symbol of the fragility of beauty, but science shows us that they can accomplish incredible feats. “There is still much to be discovered about their capabilities,” says Roger Vila, researcher at the Institute of Evolutionary Biology (CSIC-Universitat Pompeu Fabra) and co-author of the study.
With the help of the winds
The researchers modeled the energy cost of the trip and estimate that the non-stop flight across the ocean took between 5 and 8 days. This flight was energetically possible because it was facilitated by favorable wind currents. “The butterflies were only able to perform this flight by using a strategy alternating between minimal effort to avoid falling into the sea, facilitated by the ascending winds, and active flight, which requires more energy. We estimate that, without wind, The butterflies could have flown a maximum of 780 km until they had consumed all their fat and therefore their energy. explains Eric Toro-Delgado, one of the authors of the article.
Researchers highlight the importance of the Saharan air layer as a potential air dispersal highway. These wind currents, which predominate throughout the year, transport large quantities of Saharan dust from Africa to the Americas and participate in important biogeochemical cycles. However, the share of biological components transported, including living organisms, must be studied in depth.
Migration in the context of global change
This discovery suggests that there may be natural migration routes connecting continents and facilitating the dispersal of species on a much larger scale than previously thought. “This discovery opens new insights into the ability of insects to disperse over long distances, including across seas and oceans. We may be underestimating the frequency and impact of these movements on our ecosystems” , says Gerard Talavera, head of the study. “Throughout history, “Migratory phenomena have played an important role in defining the distribution of species as we observe it today,” he adds.
Research staff emphasize that with global warming and changing weather conditions, it is likely that we will see further disruptions, or even an increase in these long-distance dispersal phenomena, which could have significant consequences for biodiversity and ecosystems worldwide.
“It is essential to promote systematic monitoring routines for dispersed insects, which could help predict and mitigate the possible risks that climate change poses to biodiversity”, concludes Mr. Talavera.
Article reference:
Suchan T, Bataille CP, Reich MS, Toro-Delgado E, Vila R, Pierce NE, Talavera G. (2024). A trans-oceanic flight of over 4,200 km by painted lady butterflies. Nature Communications. DOI: doi.org/10.1038/s41467-024-49079-2
