1. Department of Ecology and Evolutionary Biology, University of California, EE Biology/EMS, Santa Cruz, CA 95064, USA
2. Center for Microbial Genetics and Genomics, Northern Arizona University, Flagstaff, AZ 86011-4073, USA
3. Department of Molecular, Cellular and Biomedical Science, University of New Hampshire, Durham, NH 03824, USA
4. Department of Biology, Boston University, Boston, MA 02215, USA