In this paper,we develop a single species evolutionary model with a continuous phenotypic trait in a pulsed pollution discharge environment and discuss the effects of pollution on the individual size of the species.The invasion fitness function of a moiiomorphic species is given,which involves the long-term average exponential growth rate of the species. Then the critical function analysis method is used to obtain the evolutionary dynamics of the system,which is related to interspecific competition intensity between mutant species and resident species and the curvature of the trade-off between individual size and the intrinsic growth rate.We conclude that,the pollution affects the evolutionary traits and evolutionary dynamics.The worsening of the pollution can lead to rapid stable evolution toward a smaller individual size,while the opposite is more likely to generate evolutionary branching and promote species diversity.The adaptive dynamics of coevolution of dimorphic species is further analyzed when evolutionary branching occurs.
