Figure 2 . Species richness across the Americas for (a ) all seed plants; (b ) only montane species; (c ) only alpine species; (d ) non-alpine species whose ranges overlapped with the same temperature and precipitation conditions as alpine species. Overall, seed plant diversity (including solely lowland species) and montane-only communities followed traditional latitudinal richness gradients, peaking near the equator. Alpine communities (panel c ), however, had their greatest diversity in the western North American cordillera and the central Andes. (d ) Non-alpine species whose ranges were otherwise climatically similar to alpine species showed the greatest concentration in Mexico and the southern United States (see Discussion). (Warmer [cooler] colors indicate greater [lower] species richness. Foreground: Mountain areas defined by the Global Mountain Biodiversity Assessment [GMBA; see Methods].Background: non-mountainous areas in the sampling region. Grey cells: missing or insufficient data. )