What is a Keystone species?
A keystone species is a species that has a strong impact on its environment or ecosystem. This impact is typically disproportionate to its abundance.
A common example is a predator that controls a herbivore, whose population growth would upset the balance of an ecosystem by consuming too much vegetation, or otherwise cause damage, such as erosion.
Another example of a keystone species are some Banksia species that are primary sources of nectar for some native Australian bird species.