1. Program in Organismic and Evolutionary Biology, University of Massachusetts, 611 North Pleasant Street, Amherst, MA 01003, USA
2. Department of Biological Sciences, Smith College, 44 College Lane, Northampton, MA 01063, USA
3. Present address: Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT 06520, USA
4. Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA
5. Department of Ecology and Evolutionary Biology, Brown University, 80 Waterman Street, Providence, RI 02912, USA
6. Biodiversity Informatics Group, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA