The tropics have more diversity of vascular plants as compared to the temperate regions because of

Latitude is the distance from equator whereas altitude is the height from sea level. The pattern of biodiversity observed in an area is also dependent of its latitudes. As one moves away from the equator or from one latitudinal region to another we notice a change in the biodiversity. The tropical rain forests found at the equator have more diversity than the temperate forests found near the poles as we move away from the equator. Therefore due to this latitudinal gradient the forests in Equador have more diversity than forest in Midwest of USA.