predator poisoning, while passive strategies rather reduce the risk of capture or ingestion through morphological alteration or aggregation. Considering the mode of action, certain active defenses represent a form of attack, e.g. Known bacterial defenses can be classified along multiple criteria. Especially for bacteria exposed to protozoan grazing, a variety of alternative defenses which can interrupt oscillations and entail shifts in predator-prey ratios have been described. A considerable amount of complexity is added to predator-prey dynamics through the appearance of grazing defense strategies. While this notion has been confirmed experimentally, the dynamics of many real-world systems hardly conform to these predictions even when external perturbations are absent. Combining experiments with mathematical modeling, we demonstrate how this succession of defenses is driven by the maximization of individual rather than population benefits, highlighting the role of rapid evolution in the breakdown of social cooperation.Ĭlassical theory predicts predator-prey systems to develop toward an equilibrium where species abundances undergo regular oscillations or coexist in a steady-state. This initial strategy, however, was consistently superseded by a second mechanism of predation defense emerging via de novo mutations. Initially, bacteria expressed a highly effective cooperative defense based on toxic metabolites, which brought predators close to extinction. Within five weeks of co-cultivation corresponding to about 35 predator generations, we observed a consistent succession of bacterial defenses in all replicates ( n = 16). Here, we explored the dynamics of a microbial predator-prey system consisting of bacterivorous flagellates ( Poteriospumella lacustris) feeding on Pseudomonas putida. This pertains especially to trade-offs and interactions between alternative defenses occurring in prey populations evolving under predation pressure. While the mechanisms and controls of many singular defenses are well understood, important ecological and evolutionary facets impacting long-term predator-prey dynamics remain underexplored. Prey organisms have developed various strategies to escape predation which differ in mode (elude vs. Predation defense is an important feature of predator-prey interactions adding complexity to ecosystem dynamics.
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