1. The Exelixis Lab, Teaching and Research Unit Bioinformatics, Department of Computer Science, Ludwig-Maximilians-University Munich Amalienstr. 17, D-80333, Munich, Germany; E-mail: stamatakis@bio.ifi.lmu.de
2. San Diego Supercomputer Center La Jolla, California, USA
3. School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne Lausanne, Switzerland