The effect of delays on the permanence for Lotka-Volterra systems Original Research Article

In this note, two examples are given to show that delays can make two-species Lotka-Volterra cooperative systems possessing an unbounded solution. This result indicates that unlike the two-species prey-predator or competitive systems, delays in cooperative ones are not harmless in the sense of permanence. These examples also give a negative answer to a recent conjecture for general n-species Lotka-Volterra delay systems proposed in [1, p. 310].