Simulation model of metapopulations and its application to competing coexistence and species richness VALLISNERIASPECIES IN LAKES OF THE MIDDLE-LOWER REACHES OF THE YANGTZE RIVER OF CHINA ON MECHANISMS OF SPECIES COEXISTENCE IN PLANT COMMUNITIES Competitive dynamics of two-metaspecies subject to the Allee-like effect Metapopulation model of multispecies competitive coexistence given exotic species invasion