1. Department of Ecology and Evolutionary Biology, University of California at Los Angeles, Los Angeles, CA 90095, USA.
2. Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA.
3. Department of Biology, Colorado State University, Fort Collins, CO 80523, USA.
4. Center for Infectious Disease Dynamics, Pennsylvania State University, University Park, PA 16802, USA.
5. Department of Ecology and Evolutionary Biology, and Woodrow Wilson School, Princeton University, Princeton, NJ 08544, USA