“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…” see more in the publication