Invasion waves in the biochemical warfare between living organisms

Landscapes of Biochemical Warfare: Spatial Self-Organization Woven from Allelopathic Interactions

Evidence shows that diversity and spatial distributions of biological communities are largely driven by the race of living organisms in their adaptation to chemicals synthesized by their neighbors. In this report, the emergence of mathematical models on pure spatial self-organization induced by biochemical suppression (allelopathy) and competition between species were investigated through numerical analysis. For both random and patched initial spatial distributions of species, we demonstrate that warfare survivors are self-organized on the landscape in Turing-like patterns driven by diffusive instabilities of allelochemicals. These patterns are simple; either all species coexist at low diffusion rates or are massively extinct, except for a few at high diffusivities, but they are complex and biodiversity-sustained at intermediate diffusion rates. "Defensive alliances" and ecotones seem to be basic mechanisms that sustain great biodiversity in our hybrid cellular automata model. Moreover, species coexistence and extinction exhibit multi-stationarity.

Community structures in allelopathic interaction networks: An ecoevolutionary approach

Evidence is mounting that the race of living organisms for adaptation to the chemicals synthesized by their neighbors may drive community structures. Here, an ecoevolutionary model for community assembly through resource competition, toxin-mediated interactions (allelopathy), and evolutionary branching is investigated. We found that stable communities with increasing biodiversity can emerge at weak allelopathic suppression, but strong chemical warfare drastically impairs diversity. For successive invasion events, the allelopathic interaction networks exhibit, respectively, Gaussian and Weibull degree distributions at weak and strong allelopathy. For the branching process dynamics, degrees scale as power laws truncated by stretched exponentials in both regimes. In addition, allelochemical interactions tend to be arranged in modules with low clustering coefficients and disassortative behavior to ensure community stability. So, in a homogeneous environment, species-rich communities can be assembled only at the context of a weak biochemical warfare between organisms, and even under this regime species interact with only a few others.