Functional diversity (ecology)

Functional diversity is a way to compare organisms based upon their traits (i.e. feeding types). Take two similar tide pools for example. One has four species of barnacle and the other has one species of starfish, urchin, seagrass, and barnacle. If species richness is compared between the two communities, it would be equal, but functional diversity says they are not equal. Because there are 4 species of barnacle in one pool versus 4 different species in the other, the first pool's functional diversity is lower. There are simply too many similar species.