1. Department of Botany, University of Wyoming , Laramie, WY , United States
2. Program in Ecology and Evolution, University of Wyoming , Laramie, WY , United States
3. Department of Zoology and Physiology, University of Wyoming , Laramie, WY , United States
4. U.S. Geological Survey, Wyoming Cooperative Fish and Wildlife Research Unit, Department of Zoology and Physiology and Program in Ecology and Evolution, University of Wyoming , Laramie, WY , United States