Global concordance in diversity patterns of vascular plants and terrestrial vertebrates.

The factors that determine large-scale patterns of species richness are poorly understood. In particular, biologists have not determined the relative roles of taxon-specific characteristics that influence diversification and distribution, and region-specific features that promote and constrain diversity. We show that the numbers of species of vascular plants and of four terrestrial vertebrate taxa (mammals, birds, reptiles and amphibians) vary in parallel across 296 geographic areas covering most of the globe, even after accounting for sample area, climate, topographic heterogeneity and differences between continents. Thus, a common set of regional characteristics and processes appears to shape patterns of species richness in a diverse set of taxa, despite substantial differences in their biological traits.