1. Department of Ecology and Evolutionary Biology, Cornell University, Corson Hall, Ithaca, NY 14853‐2701, USA
2. Portland State University, Department of Biology, P.O. Box 751, Portland, OR 97207, USA
3. Departments of Botany and Chemistry, University of British Columbia, 3510‐6270 University Blvd, Vancouver, BC, V6T 1Z4, Canada
4. Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, Turku, FI‐20014, Finland