From theory to experimental design—Quantifying a trait-based theory of predator-prey dynamics

Abstract

Successfully applying theoretical models to natural communities and predicting ecosystem behavior under changing conditions is the backbone of predictive ecology. However, the experiments required to test these models are dictated by practical constraints, and models are often opportunistically validated against data for which they were never intended. Alternatively, we can inform and improve experimental design by an in-depth pre-experimental analysis of the model, generating experiments better targeted at testing the validity of a theory. Here, we describe this process for a specific experiment. Starting from food web ecological theory, we formulate a model and design an experiment to optimally test the validity of the theory, supplementing traditional design considerations with model analysis. The experiment itself will be run and described in a separate paper. The theory we test is that trophic population dynamics are dictated by species traits, and we study this in a community of terrestrial arthropods. We depart from the Allometric Trophic Network (ATN) model and hypothesize that including habitat use, in addition to body mass, is necessary to better model trophic interactions. We therefore formulate new terms which account for micro-habitat use as well as intra- and interspecific interference in the ATN model. We design an experiment and an effective sampling regime to test this model and the underlying assumptions about the traits dominating trophic interactions. We arrive at a detailed sampling protocol to maximize information content in the empirical data obtained from the experiment and, relying on theoretical analysis of the proposed model, explore potential shortcomings of our design. Consequently, since this is a “pre-experimental” exercise aimed at improving the links between hypothesis formulation, model construction, experimental design and data collection, we hasten to publish our findings before analyzing data from the actual experiment, thus setting the stage for strong inference.

Ecosystem function in predator–prey food webs—confronting dynamic models with empirical data

“…Additionally, the timing of sampling can be important, as data from different time points can vary in how much information they contribute to the parameter estimation. To optimize data collection for parameter estimation, with regard to both frequency and timing of sampling, we recommend that pre‐experimental model analysis is performed when designing the sampling protocol (see, e.g., Banks, Banks, Rinnovatore, & Jackson, ; Laubmeier et al., ). To keep sampling rates feasible, we also suggest reducing the number of parameters to be inferred statistically.…”

Towards understanding factors influencing the benefit of diversity in predator communities for prey suppression

“…We expand the model from Schneider et al (2012), which describes intraguild interactions (intraspecific competition and intraguild predation) such that body mass determines encounter rates, feeding preferences, and metabolic constraints. We scale encounter rates according to overlap in foraging area and incorporate intraguild interference, as described in Laubmeier et al (2018). The resulting model can be applied to communities of varying size or trophic complexity, but must be restricted to generalist, ectothermic predators which reproduce on a longer timescale than their herbivore prey.…”

Trait-based modelling in ecology: lessons from two decades of research

“…Where predator-prey interactions are combined into a food web model, body size is often the central trait. This was the case in an allometric trophic network model that explicitly featured intra-and interspecific interference including predator-prey interactions in beetles and spiders (Laubmeier et al, 2018). Pathogen-host interactions resemble predator-prey interactions in many ways as demonstrated by the interactions of amphibian species and their fungal pathogens.…”