1. Present address: Department of Biology, Loyola University Chicago, Chicago, IL, USA
2. Ecology, Evolution and Behavior Program, Michigan State University, East Lansing, MI, USA
3. Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
4. Present address: Biological Sciences, University of New Hampshire, Durham, NH, USA
5. Department of Microbiology and Molecular Genetics; and Ecology, Evolution and Behavior Program, Michigan State University, East Lansing, MI, USA