Abstract
Food webs are highly complex entities. Understanding this complexity and its persistence remains one of the major challenges in ecology. Recent advances in ecological theory have pointed to the importance of interaction strength as a key to the understanding of realised food webs in nature, as opposed to the myriads of theoretically possible food webs. However, the currently used measures of interaction strength only permit a rather static 'average' point of view, which is mostly based on the assumption of equilibrium conditions. In nature, however, equilibrium conditions may be rare, with interaction strengths being highly dynamic and non-linear. Consumer densities can fluctuate, and bacteria, plants and animals can respond to the presence and density of their consumers with a variety of inducible defences. Theoretically, inducible defences have the potential to stabilise or destabilise interactions, thus affecting both population-level persistence and the integrity of the food web. Furthermore, inducible defences can temporarily decouple or modulate the interaction between trophic levels, thus affecting the balance of bottom-up versus top-down control or flows of energy. The project as a whole propose to study the effects of inducible defences on food web dynamics and persistence, with a focus on interaction strength as organising principle. Our models predict that inducible defences and diversity have a synergistic effect on food web persistence. These predictions will be tested using experimentally assembled communities, with species that also co-occur in the field. Our consortium of live theoretical ecologists and five experimental ecologists intends to study realistic inducible defence scenarios in freshwater and terrestrial systems. The project of the here proposed PhD student aims at experimentally testing our model predictions for the freshwater system. He or she will study the dynamics of simple food webs where prey species have permanent, inducible, or no defences. In addition the effects of diversity at different trophic levels on food web persistence will be explored under different scenarios.
Netherlands