FIGURE 2.

Lifespan (mean days to death) was a significant positive predictor of immune activation cost (when body mass effects were controlled); longer-lived animals experience higher immune costs. Note the inverted y-axis to convey better increasing costs with increasing lifespan. Random-effects meta-regression lines are based on conventional (blue) and phylogenetically informed (orange) models derived from a meta-regression that simultaneously modeled mass and lifespan as cost predictors (nonsignificant intercept was not included in this model) [Color figure can be viewed at wileyonlinelibrary.com]