1. Department of Biology, University of Utah, Salt Lake City, Utah 84112 USA
2. Department of Microbiology and Plant Biology, University of Oklahoma, Norman, Oklahoma 731019 USA
3. Department of Geography, University of California, Los Angeles, California 90095 USA
4. Department of Botany and Plant Sciences, University of California, Riverside, California 92521 USA
5. Institute of the Environment and Sustainability, University of California, Los Angeles, California 90095 USA