Fig. 1.

Maximum and minimum thermal-tolerance limits and range of annual extreme air and operative body temperatures as a function of latitude (A) and elevation (B–D). Warm and cool color points indicate upper and lower thermal-tolerance limits, respectively, after correcting for different acclimation temperatures. Lines indicate relationships from best-fit linear models of thermal tolerance, which take into account taxonomy and different metrics of cold tolerance. The gray region shows the range of hourly air temperatures across the year, and the light yellow region shows the range of extreme operative temperatures across the year, based on local regressions of lowland temperature data as a function of latitude (A) and on linear models of temperature as a function of latitude and elevation (B–D).