Behavioral Phases in Stochastic Multispecies Immigration-Birth-Death Processes in Competitive Ecosystems

  Nava Reinitz - Leibovich  ,  Jeremy Rothschild   ,   Anton Zilman  ,  Sidhartha Goyal  
Department of Physics, University of Toronto

Ecological competition is the struggle between organisms for the same resources. Here we assume all species are functionally identical, where the ratio between interspecific and intra-specific competition is quantified by the competitive overlap. To examine these processes, we use a stochastic approach, based on birth-death-immigration process. The species abundance distribution is regulated by both the competitive overlap and the immigration rate. Using simulations and analytical arguments, we define and investigate various behavioral phases of the stationary abundance distribution. Noteworthy, these regimes exhibit different behaviors of extinction and invasion, the dynamics of which we quantify. We find novel phases of the species abundance distribution, wherein richness fluctuations give rise to quasi-stable-species-population sizes that the system switches between. Our work presents a rich phase-space for the stationary behaviors in a competitive ecosystem. These results provide a framework for interpreting the discrepancies of abundances in ecological data of populations and inferring the underlying dynamics that shapes the communities of interacting species.