Tropical diversity gradients
“Species are distributed unevenly across the surface of Earth. More species are found in the warm tropics than in cool temperate regions. This pattern was first recognized over two centuries ago by Alexander von Humboldt, with his observation “The nearer we approach the tropics, the greater the increase in the variety of structure, grace of form, and mixture of colors, as also in perpetual youth and vigor of organic life.”
The incredible variety of form, color, and lifestyle found near the equator, and the relative paucity near the poles, is one of the most ubiquitous biological patterns on Earth, referred to as the latitudinal diversity gradient (LDG). Biodiversity, however, varies not only latitudinally but also longitudinally. Even within the species-rich tropics, some regions house fewer species than others. Tropical rain forests, for example, are the most species-rich terrestrial ecosystem on the planet, but they host comparably fewer species in Africa than in the Neotropics and Indomalaya. In PNAS, Hagen et al. use cutting-edge simulations to examine how and when differences in tropical diversity arose, which they term “pantropical diversity disparity” (PDD;). In doing so, the authors provide key insight into evolutionary mechanisms and ecosystem constraints….” see more in the publication