Variability in resource productivity drives community dynamics in intraguild predation systems

Energy transfer across trophic levels underpins community structure and stability, yet fluctuations in primary productivity challenge the persistence of species at higher trophic levels. We use an intraguild predation model-with resource, consumer, and a stage-structured predator-to show that variability in resource productivity profoundly reshapes trophic interactions and biomass distribution. We find that the amplitude of resource productivity fluctuations (ψ), rather than its period (Y), is the primary driver of dynamics. As ψ increases, the predator biomass shifts from juvenile to adult dominance and undergoes recurrent starvation-recovery cycles, which in turn regulate consumer biomass. Trophic responses to ψ are highly asymmetric: resources biomass remain largely stable, consumers biomass gain modestly, but total predator biomass declines consistently with ψ and collapses once ψ > 0.5. Both deterministic and stochastic resource variability yielded consistent results on population biomass and fluctuation amplitude. Furthermore, the system's equilibrium state-whether resource-only, consumer-resource, full coexistence, or predator-resource-was determined by the interaction between maximum resource density (R_max) and the predator's ontogenetic diet shift (θ). Critically, the amplitude ψ modulates this R_max - θ interaction, expanding or contracting the parameter regions supporting these distinct states.