About the Authors

Martin Ackermann

To whom correspondence should be addressed. E-mail: Martin.Ackermann@env.ethz.ch

Affiliations Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America , ETH Zürich, Theoretical Biology, Zurich, Switzerland

Lin Chao

Affiliation Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

MA and LC conceived and designed the experiments. MA performed the experiments, analyzed the data, and wrote the paper.