Amy E Miller1, William D Bowman2. 1. Mountain Research Station, Institute of Arctic and Alpine Research, and Department of Environmental, Population and Organismic Biology, University of Colorado, Boulder, Colorado, 80309-0334, USA. amym@colorado.edu. 2. Mountain Research Station, Institute of Arctic and Alpine Research, and Department of Environmental, Population and Organismic Biology, University of Colorado, Boulder, Colorado, 80309-0334, USA.