1. Department of Biology, University of Michigan, 830 North University Avenue, Ann Arbor, MI 48109-1048, USA
2. Département de Biochimie, Université de Montréal, C.P. 6128, Montreal, Quebec H3C 3J7, Canada
3. Department of Evolutionary Genomics, DoE Joint Genome Institute and Lawrence Berkeley National Laboratory, and Department of Integrative Biology, University of California Berkeley, 2800 Mitchell Drive, Walnut Creek, CA 94598, USA