The impact of initial evenness on biodiversity maintenance for a four-species in silico bacterial community

• We model a four species bacterial community with fully connected competition.
• The model allows initial community evenness to be varied, unlike previous studies.
• Simulation outcomes depend strongly on initial evenness and competition scheme.
• The system is generally unstable; extinction events are frequent.
• Initial evenness has a small stabilizing effect on system dynamics.

Initial community evenness has been shown to be a key factor in preserving the functional stability of an ecosystem, but has not been accounted for in previous modelling studies. We formulate a model that allows the initial evenness of the community to be varied in order to investigate the consequent impact on system diversity. We consider a community of four interacting bacterial species, and present a stochastic, spatial individual-based model simulating the ecosystem dynamics. Interactions take place on a two-dimensional lattice. The model incorporates three processes: reproduction, competition and mobility. In addition to variable initial evenness, multiple competition schemes are implemented, modelling various possible communities, which results in diverse coexistence and extinction scenarios. Simulations show that long-term system behaviour is strongly dependent on initial evenness and competition structure. The system is generally unstable; higher initial evenness has a small stabilizing effect on ecosystem dynamics by extending the time until the first extinction.