The consistency of a species’ response to press perturbations with high food web uncertainty

Abstract

Predicting species responses to perturbations is a fundamental challenge in ecology. Decision makers must often identify management perturbations that are the most likely to deliver a desirable management outcome despite incomplete information on the pattern and strength of food web links. Motivated by a current fishery decline in inland lakes of the Midwestern United States, we evaluate consistency of the responses of a target species (walleye [Sander vitreus]) to press perturbations. We represented food web uncertainty with 193 plausible topological models and applied four perturbations to each one. Frequently the direction of the focal predator response to the same perturbation is not consistent across food web topologies. Simultaneous application of management perturbations led to less consistent outcomes compared to the best single perturbation. However, direct manipulation of the adult focal predator produced a desirable outcome in 77% of 193 plausible topologies. Identifying perturbations that produce consistent outcomes in the face of food web uncertainty can have important implications for natural resource conservation and management efforts.

Informing management decisions for ecological networks, using dynamic models calibrated to noisy time‐series data

“…At the very least, our analysis suggests that it is possible, for dynamic models calibrated to time‐series data, to provide useful predictions for decision‐making. More generally, approaches such as ours that formally account for uncertainty propagation are advantageous because they can predict the probability of an undesirable outcome (Regan et al ; Tunney et al ). Our results therefore support the view that we do not need to wait until ecological models are well‐constrained in their predictions before we start forecasting (Houlahan et al ; Dietze et al ); even a model that is not particularly well‐constrained in its predictions can potentially be used for management decisions.…”

Linking net interaction effects with network topologies in food webs

“…One limitation of this study (and many previous studies, Montoya et al, 2009;Pires et al, 2020) comes from the assumption of a Holling type I (linear) functional response. Although previous studies demonstrated that net effects assuming a linear functional form could be a useful way of predicting outcomes of press perturbation (Schmitz, 1997;Tunney et al, 2017), nonlinear functional forms (Holling type II or III) can theoretically alter the direct interaction effects and consequently net effects (Novak et al, 2016) if inverse matrix approach is applied.…”

“…Thus, the existing relevant studies are restricted to very few systems. Nonetheless, several pioneering studies have shown that the outcomes of press perturbation might be closely linked to both the topologies and indirect interactions of ecological networks (Novak et al, 2011;Tunney et al, 2017). For example, when a press disturbance affects a generalist, it was found that this is unlikely to have a major effect on the population biomass of the remaining species in the food web if indirect effects are taken into account (Montoya et al, 2009).…”

Resilience: insights from the U.S. LongTerm Ecological Research Network

“…Largemouth bass populations are now essentially unmanaged in Northern Wisconsin because the primary tool of management—harvest regulation—is not impacting bass populations. It is possible that largemouth bass are important competitors or predators of young‐of‐year walleye and thereby are playing a role in the walleye decline (Hansen et al 2015 c , Tunney et al 2017), although examination of largemouth bass diets does not support this hypothesis (Kelling et al 2016).…”

“…Largemouth bass populations are now essentially unmanaged in Northern Wisconsin because the primary tool of management-harvest regulation-is not impacting bass populations. It is possible that largemouth bass are important competitors or predators of young-ofyear walleye and thereby are playing a role in the walleye decline (Hansen et al 2015c, Tunney et al 2017, although examination of largemouth Climate warming may play a role in both declining walleye and increasing largemouth bass populations in northern Wisconsin lakes. To test this hypothesis, coupled physical and fish population models were developed and calibrated for 2148 Northern Wisconsin lakes, including NTL LTER study lakes, under contemporary climate and then applied to future (2040-2089) climate projections (Hansen et al 2017).…”