[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 suggest that global maps of terrestrial vertebrate species richness are now accurate at resolutions of 100 to 200 km (3). Yet, little is known about the global patterns of genetic diversity. On page 1532 of this issue, Miraldo et al. help to fill this gap by presenting a global map of intraspecific (within-species) genetic diversity of amphibians and terrestrial mammals (4). Author: Henrique M. Pereira