1 Institute of Integrative Biology, University of Liverpool, Liverpool, L69 7ZB, UK. Electronic address: michaelb@liverpool.ac.uk.
2 National Research Council, Naples, Italy. Electronic address: c.verde@ibp.cnr.it.
3 Centre for Genome Research Institute of Integrative Biology, University of Liverpool, Liverpool, L69 7ZB, UK. Electronic address: cossins@liverpool.ac.uk.