Fig. 4

Effects on threatened species richness by human population density (Chisq_{3, 28} = 19.24, P < 0.01, R² = 0.47) and range size (Chisq_{3, 31} = 45.60, P < 0.001, R² = 0.69). The colour shade indicates species richness—the lighter the shade the higher the richness. Values of species richness were predicted by the generalized additive model in which population density and range sizes were transformed by cubic regression spline