1. Butterfly Genetics Group, Department of Zoology, University of Cambridge, CB2 3EJ Cambridge, UK; 2Laboratory of Genetics, Department of Biology, University of Turku, 20014 Turku, Finland; 3Department of Entomology, The Natural History Museum, London SW7 5BD, UK; 4Department of Biology, University of York, YO10 5DD Heslington, York, UK; and 5Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA