Evolutionary dynamics and diversification in changing environments

We use adaptive dynamics models to study how changes in the abiotic environment affect patterns of evolutionary dynamics and diversity in evolving communities of organisms with complex phenotypes. The models are based on the logistic competition model and environmental changes are implemented as a temporal change of the carrying capacity as a function of phenotype. We observe that the rate of environmental change is a crucial factor that determines whether the community survives or undergoes extinction. Surviving communities adapt to the changing conditions and converge to new stationary states, producing a diverse spectrum of evolutionary dynamics. In the majority of surviving systems we observe a reduction in the number of species, total population size and phenotypic diversity. However, for some systems with initially low number of species, slow environmental changes appear to be a driver of speciation and generate communities with higher phenotypic diversity. Phenotypes of surviving species generally evolve in the direction of the moving maximum of the carrying capacity. However, species also evolve in various phenotypic directions orthogonal to the motion of the optimum. The intensity of this undirected phenotypic dynamics increases with the rate of environmental changes.