Institute for Theoretical Biology, Humboldt University of Berlin, Berlin, Germany. ralf.steuer@hu-berlin.de|Institute for Theoretical Biology, Humboldt University of Berlin, Berlin, Germany. ralf.steuer@hu-berlin.de|Institute for Theoretical Biology, Humboldt University of Berlin, Berlin, Germany. ralf.steuer@hu-berlin.de|Institute for Theoretical Biology, Humboldt University of Berlin, Berlin, Germany. ralf.steuer@hu-berlin.de