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Abstract: Intraguild predation (IGP) is a widespread ecological phenomenon in which two consumers that share a resource also engage in a predator–prey interaction. Theory on IGP predicts the occurrence of alternative stable states, but empirical evidence of such states is scarce. This raises the question of whether alternative states are a rare phenomenon that is unlikely to be observed in nature. Here we analyze a model in which the resource exhibits logistic or chemostat dynamics and consumers have saturating (Type II) functional responses. We show that alternative states can arise for a wide range of biological scenarios and that environmental constraints can make their detection difficult. Our analysis identifies three possible combinations of alternative states: (i) IG prey or IG predator, (ii) coexistence or IG predator, and (iii) coexistence or IG prey. Bifurcation diagrams reveal that alternative states are possible over large regions of the parameter space. However, they can be limited to narrow ranges along the resource productivity axis, which may make it difficult to observe the occurrence of alternative states in communities with IGP. Microcosm experiments provide a promising avenue for detecting combinations of asymptotically stable states along a productivity gradient. [Copyright &y& Elsevier]

The article focuses on the biological behaviour of the phytoplankton cells when simulated in an allometric model. It states that phytoplankton species' structure presents large-scale geographical patterns that reflect biogeochemical processes in the ocean. Furthermore, it also notes that phytoplankton's cell size has seen a considerable adaptive trait during the cell's simulation in chemostat model. By selecting stable cell size through competition among phytoplankton, large cells present an increase in the rate of biomass production. The exploration of the evolutionary pressures on the cell size of phytoplankton with the use of ecosystem model is discussed, as well as the evolutionary stable strategies (ESS) in the model.

Ecological systems with asymptotically stable equilibria may exhibit significant transient dynamics following perturbations. In some cases, these transient dynamics include the possibility of excursions away from the equilibrium before the eventual return; systems that exhibit such amplification of perturbations are called reactive. Reactivity is a common property of ecological systems, and the amplification can be large and long-lasting. The transient response of a reactive ecosystem depends on the parameters of the underlying model. To investigate this dependence, we develop sensitivity analyses for indices of transient dynamics (reactivity, the amplification envelope, and the optimal perturbation) in both continuous- and discrete-time models written in matrix form. The sensitivity calculations require expressions, some of them new, for the derivatives of equilibria, eigenvalues, singular values, and singular vectors, obtained using matrix calculus. Sensitivity analysis provides a quantitative framework for investigating the mechanisms leading to transient growth. We apply the methodology to a predator-prey model and a size-structured food web model. The results suggest predator-driven and prey-driven mechanisms for transient amplification resulting from multispecies interactions. [ABSTRACT FROM AUTHOR]