Quantifying climatic niche breadth.
We quantified the temperature and precipitation niche breadth of each species as follows, using custom scripts in the R statistical computing environment (R Core Team, 2020) and the resulting climatic niche breadth distributions were contrasted among species occupying different elevations. Having parsed the SDMs among small increments of each climatic variable, we interpreted these climatic vectors as representing states a species could occupy within its range. We used Levins’ (1968) niche breadth index to quantify SDM uniformity across the full suite of possible climatic states for either MAT or MAP using: