Define and distinguish among native, nonnative, indicator, and keystone species and give an example of each. List six factors that threaten many species of frogs and other amphibians with extinction....

Define and distinguish among native, nonnative, indicator, and keystone species and give an example of each. List six factors that threaten many species of frogs and other amphibians with extinction. Describe the role of the American alligator as a keystone species.