1. Department of Food Safety Science, Institute of Food Research, Norwich Research Park, Colney Lane, Norwich NR4 7UA, UK
2. Evolutionary Biology Group, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
3. Computational Biology Group, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7HA, UK
4. School of Computing Sciences, University of East Anglia, Norwich NR4 7TJ, UK