The ecological species concept is controversial

Although ecological processes can explain the existence of phenetic clusters, it is controversial whether the ecological species concept is sound:

• The ecological species concept says that the members of a species can be defined by sharing a common ecological niche. However, it is common for the different life stages of an organism to have utterly different ecologies. An adult toad like Bufo americanus pictured opposite can occupy an environment very different from the one it inhabited as a tadpole.

• There has been a controversy about the processes that explain phenetic patterns in nature. Some supporters of the biological species concept have argued that interbreeding is the main explanation, whereas some ecologically minded critics have emphasized selection, due to ecological patterns.