1. Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520–8106, USA.
2. Department of Geological Sciences, University of Idaho, Moscow, ID 83844–3022, USA.
3. College of Environmental Science and Forestry, State University of New York, Syracuse, NY 13210, USA.
4. Yale Institute of Biospheric Studies, Yale University, New Haven, CT 06520-8106, USA.