1. Simons Center for Quantitative Biology; Cold Spring Harbor Laboratory; Cold Spring Harbor New York 11724 USA
2. Department of Botany; National Museum of Natural History, MRC 166; Smithsonian Institution; Washington D.C. 20013 USA
3. Department of Biology and Microbiology; South Dakota State University; Brookings South Dakota 57007 USA
4. Department of Natural Resource Management; South Dakota State University; Brookings South Dakota 57007 USA