Interaction strength and stability in stage‐structured food web modules

Abstract

There has been a long‐standing debate on what creates stability in food webs. One major finding is that weak interactions can mute the destabilizing potential of strong interactions. Considering that stage structure is common in nature, that existing studies on stability that include population stage structure point in different directions, and the recent theoretical developments in the area of stage structure, there is a need to address the effects of population stage structure in this context. Using simple food web modules, with stage structure in an intermediate consumer, we here begin to theoretically investigate the effects of stage structure on food web stability. We found a general correspondence to previous results such that strong interactions had destabilizing effects and weak interactions that result in decreased energy flux had stabilizing effects. However, we also found a number of novel results connected to stage structure. Interestingly, weak interactions can be destabilizing when they excite other interactions. We also found that cohort cycles and predator–prey cycles did not respond in the same way to increasing interactions strength. We found that the combined effects of two predators feeding on the same prey can strongly destabilize a system. Consistent with previous studies, we also found that stage‐specific feeding can create a refuge effect that leads to a lack of strong destabilization at high interaction strength. Overall, stage structure had both stabilizing and destabilizing aspects. Some effects could be explained by our current understanding of energetic processes; others need additional consideration. Additional aspects such as shunting of energy between stages, control of biomass fluxes, and interactions between lags and energy flux, should be considered.

Diversity and coexistence are influenced by time‐dependent species interactions in a predator–prey system

“…However, what appears to be less broadly appreciated is that the stability of predator–prey systems is context dependent. For example existing studies have found that strong interactions can stabilise small food webs, but destabilise larger ones (Gross et al 2009), and that results can vary depending on stage structure (Nilsson et al 2018). Likewise, adaptive foraging (Visser et al 2012) or defence traits (Kondoh 2007) might increase stability even in the presence of strong interactions.…”

Causes and consequences of ontogenetic dietary shifts: a global synthesis using fish models

“…Studies attempting to address these knowledge gaps (e.g. Takimoto, ; Schellekens et al, ; Nakazawa, ; Wollrab et al, ; Nilsson et al, ) have largely focused on theoretical approaches. Although some empirical attempts have been made to explore the implications of ODSs on consumer–resource and food‐web dynamics (e.g.…”

“…Understanding stability in stage‐structured food webs is an emerging field in ecology, and much attention is being paid to identify and disentangle the contributing factors (de Roos & Persson, ; Caskenette & McCann, ; Nilsson et al, ). Theory predicts that ODSs and stage‐structured populations are key determinants of food‐web stability (de Roos & Persson, ; Nilsson et al, ).…”

“…Understanding stability in stage‐structured food webs is an emerging field in ecology, and much attention is being paid to identify and disentangle the contributing factors (de Roos & Persson, ; Caskenette & McCann, ; Nilsson et al, ). Theory predicts that ODSs and stage‐structured populations are key determinants of food‐web stability (de Roos & Persson, ; Nilsson et al, ). Indeed, in accordance with biomass reallocation theory (see de Roos & Persson, ), Caskenette & McCann () recently demonstrated that stage‐structured predators increase the stability of food webs.…”

“…Werner & Hall, ; Wu & Culver, ). Theory predicts that ODSs are influential in community and food‐web stability (Schellekens et al, ; Miller & Rudolf, ; Rudolf & Lafferty, ; de Roos & Persson, ; van Leeuwen et al, , ; Nilsson, McCann & Caskenette, ), but we currently lack a holistic understanding based on empirical evidence of their consequences for populations, communities, food‐web dynamics and ecosystem processes and functioning. Because morphological, behavioural, physiological and life‐history traits play an important role in foraging specialisation and define intra‐specific trophic polymorphisms where they exist [Smith & Skúlason, and references therein], identification of the role of traits linked with foraging should help to disentangle the causes and consequences of ODSs.…”