Global gradients in vertebrate diversity predicted by historical area-productivity dynamics and contemporary environment

Broad-scale geographic gradients in species richness have now been extensively documented, but their historical underpinning is still not well understood. While the importance of productivity, temperature, and a scale-dependence of the determinants of diversity is broadly acknowledged, we here argue that limitation to a single analysis scale and data pseudoreplication have impeded an integrated evolutionary and ecological understanding of diversity gradients. We develop and apply a hierarchical analysis framework for global diversity gradients that incorporates an explicit accounting of past environmental variation and provides an appropriate measurement of richness. Due to environmental niche conservatism organisms generally reside in climatically defined bioregions, or “evolutionary arenas”, characterized by in situ speciation and extinction. These bioregions differ in age and their total productivity and have varied over time in area and energy available for diversification. We show ...