Figure 3 . Density histograms of the temperature (MAT) and precipitation (MAP) niche space occupied at the center of species’ ranges for (a ) all seed plants in our dataset; (b ) only lowland species; (c ) only montane species; (d ) only alpine species. Warmer (cooler) colors indicate greater (fewer) species with that combination of niche parameters. Univariate histograms for each climate variable are given along plot margins.