Fig. 2: On average, environmental conditions explain more of the variance in bird and mammal diversity than biogeographic isolation.

For each metric, total variance explained includes the variance explained by biogeographic isolation only (red), environment only (including climate, elevation, topography, and landmass area variables; blue), and shared between biogeographic isolation and environment (not shown). Variance explained was calculated by comparing adjusted R² values among a biogeographic isolation model, an environment model, and a global model that included both biogeographic isolation and environment variables.