However, we are certain that tropical forests contain a great many species and most are unknown to science. We also know that the tropics are highly diverse based on evidence from well-studied groups, including the vertebrates and flowering plants. Whenever one compares the number of species along a latitudinal gradient, one observes a trend of increasing numbers of species towards the equator. We only have partial answers. One class of answers centers around the spectacular specialization we observe in tropical forests.
Tropical species exhibit highly specialized roles.
However, this begs the question of how these species became so specialized and diverse, and here we turn to an evolutionary perspective. First, let's examine two examples of the high degree of specialization found in tropical forests. The forests themselves are multi-layered. A temperate forest usually is two or three layered. In an undisturbed forest the trees are fairly similar in height, there usually is some ground vegetation, and in between there may or may not be a shade-adapted middle layer.