image: A painted lady butterfly (Vanessa cardui) refueling in Morocco, before embarking on the long journey northwards to southern Europe. view more
Credit: Image credit: Oriol Massana Valeriano (photographer).
Winter rainfall in sub-Saharan Africa limits the size of painted lady butterfly migrations to Europe in the spring, according to a study. Every spring, painted lady butterflies (Vanessa cardui) arrive in southern Europe as part of an annual, multigenerational migration circuit stretching from Scandinavia to sub-Saharan Africa. The size of migrating populations varies, increasing a hundredfold in some years, but the reason for the variation is unclear. Gao Hu, Constanti Stefanescu, Jason W. Chapman, and colleagues combined winter and spring environmental data covering critical regions in Africa and Europe, 21 years of butterfly population records from the Mediterranean and Northwestern Europe, and atmospheric trajectory simulations along migratory routes to model interannual fluctuations in painted lady breeding cycles. The authors found that a major driver of large painted lady migrations is winter conditions in sub-Saharan West Africa, where unusually high rainfall can produce an abundance of vegetation for emerging larvae during an otherwise dry season. In late winter and early spring, atmospheric conditions allow the butterflies to engage in long-range windborne migration across the Sahara Desert to Northwest Africa, where the next generation of butterflies emerge in March and April before migrating to southern Europe. According to the authors, changing rainfall patterns in sub-Saharan Africa are likely to have unpredictable effects on the Afro-European migratory circuit of painted lady butterflies.
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Article #2021-02762: "Environmental drivers of annual population fluctuations in a trans-Saharan insect migrant," by Gao Hu, Constanti Stefanescu, et al.
MEDIA CONTACTS: Jason Chapman, University of Exeter, UNITED KINGDOM; tel: +44 (0)7740 166107; email: <j.chapman2@exeter.ac.uk>; Gao Hu, Nanjing Agricultural University, Nanjing, Jiangsu, CHINA; email: <hugao@njau.edu.cn>; Constanti Stefanescu, Natural Sciences Museum of Granollers, Catalonia, SPAIN; email: <canliro@gmail.com>
Journal
Proceedings of the National Academy of Sciences