Resource utilization determines growth rates and evolution in simple multi-species evolutionary model.

Species proliferate in an ecosystem if resources are abundant. Populous species at the same time deplete resources, which undermines their expansion. This suggests that resource utilization, appropriately quantified, should set their growth rate. By defining a species by the amount of different resources it consumes, and using the alignment of this vector with the vector of available resources as species growth rate, we can implement growth but also drift in species composition, and hence entire ecosystem evolution through speciation and adaptation. Our approach displays all the salient features of ecosystem evolution. We can evolve ecosystems even by initiating dynamics out of a single primordial ancestor. Despite the nonlinear and stochastic nature of this MacArthur-style approach, the modeling approach yields a robust, universal solution for the mean ecosystem fitness dynamics that is resilient against resource shocks. More generally, ecosystem fitness depends in an intuitive way on model parameters such as resource influx, reproduction rate and evolutionary noise. Our resource utilization approach to growth modeling so provides a general but simple starting point to evolutionary ecosystem dynamics.