1. Department of Plant Biology and W.K. Kellogg Biological Station, Michigan State University, East Lansing, Michigan 48824;
2. W.K. Kellogg Biological Station and Department of Zoology, Michigan State University, Hickory Corners, Michigan 49060;
3. Department of Environmental Science and Policy, University of California, Davis, California 95616;
4. Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824;
5. Section of Ecology, Behavior, and Evolution, University of California, San Diego, La Jolla, California 92093;