RESULTS:

• Annual precipitation and plant productivity = best effect

• Maximum July temps and elevation= some effect

• Minimum January temps = no effect

• It appears that overall, pikas are responding to climate change by elevation shifts, not body size evolution.

I found distinct differences between several but not all of the pika populations. The Cascade and Southern Rockies populations are similar to eachother and to Wasatch, but larger than all others. The mean body mass of Northern Rockies overlapped with Wasatch and no one else. The Sierra pika population is distinctly smaller than all other populations. I found that the climate and environmental variables explained little of the body size variation found in pikas. The best predictors of pika body mass were precipitation (R squared = 0.094, p < 0.0001) and net primary productivity (R squared = 0.077, p < 0.0001). Elevation (R squared = 0.022, p < 0.0001) and July maximum (R squared = 0.007, p < 0.0064) temperature explained some variation in body mass, and January minimum temperature explained none (R squared = 5.364e-5, p = 0.81).