1. Department of Integrative Biology; University of Texas; Austin TX 78712 USA
2. Department of Entomology; University of California; Riverside CA 92521 USA
3. Department of Biological Sciences; University of Alabama; Tuscaloosa AL 35401 USA
4. Evolution, Behaviour & Environment; School of Life Sciences; University of Sussex; Falmer East Sussex BN1 9QG UK
5. Department of Life Sciences; Natural History Museum; London SW7 5BD UK
6. USDA-ARS; Pollinating Insect Research Unit; Utah State University; Logan UT 84322 USA