1. Department of Ecology & Evolutionary Biology; University of California, Irvine; 321 Steinhaus Hall Irvine California 92697 USA
2. Canyonlands Research Station; Southwest Biological Science Center, United States Geological Survey; 2290 S West Resource Boulevard Moab Utah 84532 USA
3. Department of Geography and GIS; University of Cincinnati; 401 Braunstein Hall Cincinnati Ohio 45221 USA
4. Saguaro National Park; 3693 South Old Spanish Trail Tucson Arizona 85730 USA