[Perspective] A latitudinal gradient for genetic diversity

The tropics have by far the highest species diversity on Earth. Over two-thirds of terrestrial vertebrates occur in tropical moist forests (1). The species diversity is also highest in the tropics for several other taxa, such as vascular plants and arthropods, and in other realms, including freshwater and marine ecosystems. These latitudinal gradients were described decades ago (2), but recent work has yielded detailed knowledge of species-richness patterns. For example, Hurlbert and Jetz sugges