Institute for Theoretical Biology, Humboldt University Berlin, Invalidenstraße 43, D-10115 Berlin, Germany. r.lehmann@biologie.hu-berlin.de|Institute for Theoretical Biology, Humboldt University Berlin, Invalidenstraße 43, D-10115 Berlin, Germany. r.lehmann@biologie.hu-berlin.de|Institute for Theoretical Biology, Humboldt University Berlin, Invalidenstraße 43, D-10115 Berlin, Germany. r.lehmann@biologie.hu-berlin.de|Institute for Theoretical Biology, Humboldt University Berlin, Invalidenstraße 43, D-10115 Berlin, Germany. r.lehmann@biologie.hu-berlin.de|Institute for Theoretical Biology, Humboldt University Berlin, Invalidenstraße 43, D-10115 Berlin, Germany. r.lehmann@biologie.hu-berlin.de|Institute for Theoretical Biology, Humboldt University Berlin, Invalidenstraße 43, D-10115 Berlin, Germany. r.lehmann@biologie.hu-berlin.de