title: Long-distance autumn migration across the Sahara by painted lady butterflies: exploiting resource pulses in the tropical savannah.
abstract: The painted lady, Vanessa cardui, is a migratory butterfly that performs an annual multi-generational migration between Europe and North Africa. Its seasonal appearance south of the Sahara in autumn is well known and has led to the suggestion that it results from extremely long migratory flights by European butterflies to seasonally exploit the Sahel and the tropical savannah. However, this possibility has remained unproven. Here, we analyse the isotopic composition of butterflies from seven European and seven African countries to provide new support for this hypothesis. Each individual was assigned a geographical natal origin, based on its wing stable hydrogen isotope (δ2Hw) value and a predicted δ2Hwbasemap for Europe and northern Africa. Natal assignments of autumn migrants collected south of the Sahara confirmed long-distance movements (of 4000 km or more) starting in Europe. Samples from Maghreb revealed a mixed origin of migrants, with most individuals with a European origin, but others having originated in the Sahel. Therefore, autumn movements are not only directed to northwestern Africa, but also include southward and northward flights across the Sahara. Through this remarkable behaviour, the productive but highly seasonal region south of the Sahara is incorporated into the migratory circuit of V. cardui.
authors.affiliation: Natural History Museum of Granollers, Francesc Macià, 51, 08402 Granollers, Spain CREAF, 08193 Cerdanyola del Vallès, Spain canliro@gmail.com.
authors.forename: Constantí
authors.identifier: 0000-0001-8952-7869
authors.initials: C
authors.lastname: Stefanescu
authors.affiliation: Environment Canada, 11 Innovation Boulevard, Saskatoon, Saskatchewan, Canada S7N 3H5.
authors.forename: David X
authors.initials: DX
authors.lastname: Soto
authors.affiliation: Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Passeig Marítim de la Barceloneta, 37, 08003 Barcelona, Spain Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Gerard
authors.initials: G
authors.lastname: Talavera
authors.affiliation: Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Passeig Marítim de la Barceloneta, 37, 08003 Barcelona, Spain.
authors.forename: Roger
authors.initials: R
authors.lastname: Vila
authors.affiliation: Environment Canada, 11 Innovation Boulevard, Saskatoon, Saskatchewan, Canada S7N 3H5 Department of Biology, University of Western Ontario, London, Ontario, Canada N6A 5B7.
authors.forename: Keith A
authors.initials: KA
authors.lastname: Hobson
mesh_terms: D000349:Africa; D025041:Animal Migration; D000818:Animals; D002080:Butterflies / Q000502:physiology*; D005060:Europe; D065948:Grassland; D012621:Seasons; D014921:Wings, Animal / Q000737:chemistry
keywords: Sahara; Vanessa cardui; deuterium; insect migration; isoscapes; tropical savannah