Figure 3.

The trait disparity value at a given point in time (actual data, solid line; expected from phylogenetic simulations, dashed line) is the ratio of the average disparity of subclades for which ancestral lineages were present at that time relative to the disparity of all mammals. Age (Ma) is calibrated in millions of years before the present. Toward the tips, a large proportion of the variation in thermal environments occurs within mammal clades (high relative disparity). Towards the root, most variation in thermal environment is between mammal clades (low relative disparity).