It is often proposed that a feature that is advantageous to individual organisms is the reason for the great number of species in certain clades. For example, wings have been postulated to be a cause of the great diversity of winged insects compared with the few species of primitively wingless insects.
(1) How could an individually advantageous feature cause greater species diversity?
(2) How can one test a hypothesis that a certain feature has caused the great diversity of certain groups of organisms?
(3) What metrics would you use to determine that your hypothesis is correct?