Persistence and extinction for general nonautonomous n-species Lotka-Volterra cooperative systems with delays

The general nonautonomous n-species Lotka-Volterra cooperative systems with varying-time delays are studied. Sufficient conditions for the uniform strong persistence, uniform weak average persistence, uniform strong average persistence, and extinction of populations are obtained by applying the method of Liapunov functionals. Particularly, when the intrinsic growth rate of a species is nonpositive, the species can be persistent or extinct under the same given assumptions.