With the help of innovative interdisciplinary methods, scientists have shown for the first time that burdock butterflies are capable of making transatlantic flights of more than 4,200 kilometers and reaching the coast of South America.

Burdock (Vanessa Cardui) is one of the most famous wandering butterflies. These species, which live almost everywhere in the world, especially in Russia, are not usually found in South America. However, on the Atlantic coast of French Guiana, Gerard Talavera noticed a flock of these butterflies (Gerard Talavera), a researcher from the Barcelona Botany Institute at the Spanish Supreme Council for Scientific Research (CSIC).

An unusual meeting outside the traditional burdock varieties attracted the scientist’s attention. Together with colleagues from Spain, Poland, Canada and the USA, he decided to find out where these butterflies come from in South America. The research was published by a journal Nature Communication .

The study’s authors hypothesized that burdocks came to French Guiana either from North America, where the closest populations live, or from Africa or Europe. By analyzing the direction of the winds around the time the butterflies were spotted on the beach, scientists discovered persistent air currents from West Africa that may have contributed to the burdocks’ trans-Atlantic flight.

The next stage was the genetic study of several individuals captured in French Guiana. Butterflies were kept in envelopes made of varnished paper for further analysis. Sequencing their genomes and comparing them with representatives of other populations showed that they are genetically closer to the African and European burdock.

Experts thus ruled out the possibility of a North American origin and strengthened the version about a journey across the ocean. In its favor is the fact that the burdocks caught in South America, before falling into the hands of scientists, lay with their wings open on the sand a few meters from the waterline and looked miserable.

Additionally, DNA analysis of pollen from the bodies of butterflies allowed us to identify pollen grains from two plant species that grow only in Tropical Africa. This proved that burdocks collected nectar from flowers in that area before their trans-Atlantic flight.

Finally, the researchers examined stable hydrogen and strontium isotopes obtained from burdock wings. Wings retain isotopic characteristics specific to where butterflies develop in the larval stage.

Similar signatures were found in all evaluated individuals, indicating their common origin. Based on the results of the analysis, it was possible to establish that the probable homeland of the insects is Western European countries such as France, Ireland, Great Britain or Portugal, or West Africa.

“Ripyanitsa arrived from West Africa to South America, flying at least 4,200 kilometers across the Atlantic. However, if they start from Europe and cross three continents, the journey can be even longer. Thus, the length of their migration can reach 7,000 kilometers or more. “It’s a remarkable achievement for the insect,” he said.

To assess whether butterflies are capable of such a transatlantic flight, scientists calculated the potential energy costs and duration of the journey. It turns out that a non-stop flight across the ocean will take five to eight days. For burdock, this is only possible if there is a favorable tailwind. The authors concluded that without this, butterflies can fly a maximum of 780 kilometers, expending all their fat reserves, that is, their energy.

The researchers’ discoveries point to the existence of natural air corridors between continents that could facilitate the spread of species on a much larger scale than previously thought. Additionally, for the first time, a combination of molecular techniques including isotopic geolocation and pollen metabar coding was used to study insect migration.

The results of the study are encouraging and apply to many other migratory species. According to the authors, such a comprehensive approach would fundamentally change the perception of insect migration.