Environment- and system-specific interactions between population and trait dynamics

Understanding population dynamics across environmental contexts is essential to predict ecosystem stability. Functional traits influence population growth, which can in turn influence the traits and thus create feedback between population and trait dynamics. Here, by augmenting models of population and trait change with trait and population information, respectively, we demonstrate that such feedback occurred in an autotrophic but not in a heterotrophic microbial system. Furthermore, exposure to a pollutant disrupted this feedback: trait change and population growth ceased to interact in either system. Finally, when the models augmented with trait/population information were superior, the improvement was substantial, showing that density-trait feedbacks are potentially large, even though they are system- and environment-specific.