A trans-oceanic flight of over 4,200 km by painted lady butterflies

The extent of aerial flows of insects circulating around the planet and their impact on ecosystems and biogeography remain enigmatic because of methodological challenges. Here we report a transatlantic crossing by Vanessa cardui butterflies spanning at least 4200¿km, from West Africa to South America (French Guiana) and lasting between 5 and 8 days. Even more, we infer a likely natal origin for these individuals in Western Europe, and the journey Europe-Africa-South America could expand to 7000¿km or more. This discovery was possible through an integrative approach, including coastal field surveys, wind trajectory modelling, genomics, pollen metabarcoding, ecological niche modelling, and multi-isotope geolocation of natal origins. The overall journey, which was energetically feasible only if assisted by winds, is among the longest documented for individual insects, and potentially the first verified transatlantic crossing. Our findings suggest that we may be underestimating transoceanic dispersal in insects and highlight the importance of aerial highways connecting continents by trade winds.

This work was funded by the National Geographic Society (grant WW1-300R-18), by the British Ecological Society (grant LRB16/1015), by the PRIC grants of the Fundació Barcelona Zoo, by the grant LINKA20399 from the CSIC iLink program, by the grant 2021-SGR-01334 from the Departament de Recerca i Universitats (Generalitat de Catalunya), and by the grant PID2020-117739GA-I00 MCIN/AEI/10.13039/501100011033 to G.T.; by Grant NFRE-2018-00738 of the New Frontiers in Research Fund (Government of Canada) to C.P.B. and G.T.; by grant FPU22/02358 from the Spanish Ministry of Science, Innovation and Universities to E.T.-D; and by project PID2022-139689NB-I00 (MCIN/AEI/ 10.13039/501100011033 and by ERDF, EU) and by grant 2021-SGR- 00420 from the Departament de Recerca i Universitats (Generalitat de Catalunya) to R.V. G.T. and N.E.P. also acknowledge the Putnam Expeditionary Fund from the Museum of Comparative Zoology (MCZ, Harvard University).

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