About the Authors
Department of Ecology and Evolution, University of Chicago, Chicago, Illinois, United States of America
Department of Plant Biology, Michigan State University, East Lansing, Michigan, United States of America
Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois, United States of America
The authors have declared that no competing interests exist.
Conceived and designed the experiments: JB. Performed the experiments: XZ AC. Analyzed the data: XZ SS AC JB. Wrote the paper: XZ SS JB.