Competitive Exclusion Principle

The competitive exclusion principle, also known as Gause's law, states that two species competing for exactly the same limiting resource within the same ecological niche cannot stably coexist indefinitely, because even a small competitive advantage will eventually allow one species to displace the other. The principle is named for Soviet biologist Georgy Gause, whose 1934 laboratory experiments growing competing species of Paramecium in shared culture demonstrated the effect directly, though related ideas had been anticipated earlier by researchers including Joseph Grinnell. The principle underlies the modern ecological concept of niche differentiation, since species observed to coexist over the long term are understood to have evolved sufficiently distinct resource use, habitat or behavior to avoid direct competitive exclusion. It remains a foundational, though not unqualified, organizing idea in community ecology, with real-world coexistence often explained by factors, such as fluctuating environments, that complicate the principle's simplest form.