Why is much of the tropics considered as a biodiversity hotspot?

Well the term hotspot is any place with at least 1500 types of vascular plants that are uniquely occurring in that area. https://www.learner.org/courses/envsci/unit/text.php?unit=9&secNum=4 Tropical plants can’t thrive in places that aren’t tropical. Palm trees can’t grow in Detroit. Tropical rain forests have the distinction of having thousands of different plants and tens of thousands of different animals that don’t occur in other parts of the world. That and the diversity in plant life would satisfy the definition of a biodiversity hotspot. http://www.eoearth.org/view/article/150650/ All the animals in the tropics have adapted to live in the tropics, they can’t transplant to Fargo, North Dakota and survive there. Many of them, such as the poison dart frog need to keep their skin moist through the humidity of the rain forest and will die without it. Evolution has permanently affixed these animals and plants to living in this one biosphere.