1. Department of biology, BOX 90338, Duke University, Durham, NC 27708, U.S.A.
2. Departments of Entomology and Biology, Plant Sciences Building, University of Maryland, College Park, MD 20742, U.S.A.
3. Institute of Ecology, 517 Biological Sciences Bldg., University of Georgia, Athens, GA 30602, U.S.A.
4. Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, P.O. Box 38, Solomons, MD 20688, U.S.A.
5. School of Natural Resources & Environment, University of Michigan, Ann Arbor, MI 48109, U.S.A.
6. Department of Biology, University of New Mexico, Albuquerque, NM 87131, U.S.A.
7. Department of Fish and Wildlife Resources, University of Idaho, Moscow, ID 83844, U.S.A.
8. Department of Geography, McCone Hall, University of California, Berkeley, CA 94720, U.S.A.
9. Center for Ecohydraulic Research, College of Engineering, 322 E. Front St., Suite 340, University of Idaho, Boise, ID, U.S.A.