Gause’s ‘competitive exclusion principle’ states that two closely related species competing for the same resources cannot coexist indefinitely and the competitively inferior on will be eliminated eventually (true if resources are limiting). This principle has been modified to ‘complete competitors cannot coexist’ one of the primary ways niche-sharing species can coexist is the competition-colonisation trade-off. In simple terms, species that are better competitors will be specialists, whereas species that are better colonisers are more likely to be generalists.