Some, known as keystone species, play a role in ecosystems that seems out of proportion to their number, such that even small changes in their abundance may have great impacts on the ecosystems in which they live.

• 一些已知的重要物种，在生态系统中扮演的角色超出他们在数量上的比例。 这样的话，即使数量上很少的变化对他们所居住地方的生态系统也会产生很大的影响。