1. Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
2. School of Biology, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
3. Division of Neuroscience, Medical Research Institute, Ninewells Medical School, University of Dundee, Dundee DD1 9SY, UK.
4. School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA.
5. Jodrell Laboratory, Royal Botanic Gardens, Kew, Surrey TW9 3AB, UK.
6. Natural Resources Institute, University of Greenwich, Chatham, Kent ME4 4TB, UK.