The Importance of Life History and Population Interactions in Population Growth

Population interactions are the centerpiece of many ecological studies. Especially the roles of competition and predation on populations on dynamics and evolution have remained a hot topic since Lotka and Volterra’s classical works. However, understanding how these population interactions are interacting with each other has remained elusive. We tested the hypothesis of Gurevitch that predation will stabilize an ecosystem, because it should decrease competition via removing resource consumers from the system. In a top-down model, we show that implementing even just a few life history parameters, the population will stay below their carrying capacity, which automatically dampen the effect of competition. Therefore, a decrease of competition can happen without predators. Our bottom-up, agent-based model predicted then that predation actually fosters the removal of one competing prey species from the system. A longer coexistence of preys can only be observed if they occupy different niches. In this case, the effect of predation is not only more moderate, but it will increase the survivability of the predators as well. We emphasize the importance of implementing life history parameters (e.g., mating success, sex ratio, density-independent death) into the population models to find more reliable predictions.