Simple Seasonal Switches in Food Web Composition Unveil the Complexity of an Arctic Predator-Prey System

AbstractLife has evolved different strategies to take advantage of seasonal changes in the environment that are emblematic of boreal and arctic biomes. However, ecological theories often ignore seasonal changes for tractability or simplicity. Understanding the effect of seasonality may prove crucial as the changing climate puts more pressure on ecosystems. Hybrid dynamical models are an efficient way to represent seasonal adaptations where switches in food web compositions account for species migrations and predator movements. We use the highly seasonal and cyclic dynamics of an Arctic food web to showcase the utility of hybrid models. The simplified representation of community dynamics provided by the hybrid framework eases the study of conditions leading to lemming cycles and facilitates parameterization with empirical data. We corroborate that seasonal switches, accounting for the onset of reproduction of resident predators and the migration of mobile predators, likely drive cyclic fluctuations in lemming abundance. Our empirical investigation reveals that each predator alone does not reduce lemming growth rate enough to generate population cycles, which reinforces the idea that the predator community as a whole is responsible for the cyclic dynamics. This situation arises because each predator has unique adaptations to seasonality and impacts the dynamics in different but complementary ways. Our results have implications for community ecology, as they show how hybrid models can help understand complex dynamics in highly seasonal ecosystems. This is especially relevant in the Arctic, considering that rapid warming has the potential to disrupt lemming population cycles and negatively affect their predators.