1. Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan 48109, USA;
2. Department of Microbiology and Plant Pathology, Institute for Integrative Genome Biology, University of California, Riverside, California 92521, USA;
3. Laboratory of Genetics, DOE Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, Center for Genomic Science and Innovation, J.F. Crow Institute for the Study of Evolution, University of Wisconsin–Madison, Madison, Wisconsin 53726, USA;
4. Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235, USA;