In October 2013, Gerard Talavera, a researcher from the Botanical Institute of Barcelona at CSIC, discovered Painted Lady Butterflies on the Atlantic beaches of French Guiana, a species not typically found in South America. This unusual sighting led to an international study to investigate the origin of these butterflies. A team of researchers from various institutions employed innovative multidisciplinary tools to track the journey and origin of these mysterious Painted Ladies. They reconstructed wind trajectories and found favorable conditions for a transatlantic crossing from western Africa, suggesting that the butterflies might have flown across the entire ocean.
The researchers sequenced the genomes of the butterflies and compared them to populations globally, finding closer genetic relatedness to African and European populations, ruling out the possibility of their origin in North America, thus reinforcing the hypothesis of an oceanic journey. They used next-generation molecular techniques to analyze pollen grains carried by the butterflies, identifying two plant species from tropical Africa which indicated that the butterflies nectared on African flowers before their transatlantic journey. By analyzing hydrogen and strontium isotopes in the butterflies’ wings, along with a model of larval growth habitat suitability, they determined a potential natal origin in western Europe, such as France, Ireland, the United Kingdom, or Portugal.
The study reveals the methodological novelty of combining molecular techniques, isotope geolocation, and pollen metabarcoding on migratory insects. This approach is considered promising and transferable to other migratory insect species, potentially transforming understanding of insect migration. The researchers emphasized the need for continued monitoring of dispersing insects to predict and mitigate potential risks to biodiversity resulting from global change. The potential impact of migrations in the context of global change highlights the importance of assessing the dispersal abilities of insects, which may have a more significant impact on ecosystems than previously estimated.
The researchers further assessed the feasibility of a transatlantic flight by analyzing the energy expenditure for such a journey. They predicted that the butterflies, utilizing a strategy of alternating between active flight and gliding with wind, could make the 5 to 8-day flight over the ocean without stops due to favorable wind conditions. The study also highlighted the significance of the Saharan air layer as an aerial route for dispersion, noting that these wind currents can transport living organisms, expanding the understanding of natural aerial corridors connecting continents and potentially facilitating the dispersal of species on a larger scale.
By underlining the importance of migratory phenomena in shaping species distributions, researchers emphasize the need for systematic monitoring of dispersing insects to predict and mitigate potential risks to biodiversity. With the impact of global warming and changing climate patterns, researchers predict an increase in long-distance dispersal events, which could significantly impact biodiversity and ecosystems worldwide. This study represents a significant contribution to understanding the capabilities of butterflies and the potential implications of their long-distance migrations in the context of a changing climate.
