Temperature triggers a non‐linear response in resource–consumer interaction strength

Abstract

Although temperature is recognized as a major determinant of many ecological processes, it is still not clear whether temperature increase caused by climate change will strengthen or weaken species interactions. One hypothesis is that interactions will respond non-monotonically to temperature because thermal performance curves, which determine the strength of these interactions, are also non-monotonic. To evaluate this hypothesis, we developed a temperature-dependent consumer-resource model and tested predictions from this model in large freshwater mesocosms populated with green algae (Chlorella vulgaris) and herbivorous zooplankton (Daphnia magna). We found both in the model simulations and empirical investigations that the suppressive effect of the consumer depended non-monotonically on the temperature. As predicted by the model, Daphnia suppressed the algal maximum per capita growth rate at the temperature that maximized algal growth rate but had little effect on resource growth at either lower or higher temperatures. This finding could help explain why effects of temperature variation on species interaction are variable in the literature and suggests that predicting the effects of temperature on the strength of food web interactions requires knowledge of the thermal performance curves for multiple traits, for multiple species and over a range of temperatures.

Theory of temperature-dependent consumer-resource interactions

“…However, at lower temperatures, unimodal and monotonic thermal dependencies produce contrasting warming-stability relationships. Therefore, the temperatures currently experienced by communities relative to their optimal temperature will determine the impact of warming on stability (Betini et al 2019) in combination with the thermal dependence shape of the functional response.…”

“…Using data on specific rates (e.g. attack, ingestion and metabolic rates), studies have inferred that stability either increases monotonically (Rall et al 2010(Rall et al , 2012Vucic-Pestic et al 2011;Fussmann et al 2014) or responds unimodally (Sentis et al 2012;Betini et al 2019) to warming. Theoretical work on stability, in particular on the mechanisms causing the onset of oscillations, expands decades (Rosenzweig & MacArthur 1963;Rosenzweig 1971;May 1972).…”

“…Our framework can be applied to both static and dynamic properties of the consumer-resource interactions. We illustrate this application using consumer-resource biomass ratio and a stability metric quantifying the proximity to oscillations, respectively; these two variables dominating the literature on the effects of warming on consumer-resource communities and food webs (Vasseur & McCann 2005; Rall et al 2008; Vucic-Pestic et al 2011; Uszko et al 2017; Betini et al 2019). We implement different thermal parameterisations from the literature to elucidate how the relative importance of different parameters and their varying thermal dependence shapes impact predictions about the effects of warming on consumer-resource interactions.…”

Thermal mismatches in biological rates determine trophic control and biomass distribution under warming

“…Such mismatches in thermal curves of interacting species have been widely reported (Dell et al, 2011) and shown to strongly influence species interactions under warming (Archer et al, 2019;Betini et al, 2019;Bideault et al, 2019;Dell et al, 2014;Laws & Joern, 2013;Sentis, Binzer, et al, 2017). For instance, autotrophic and heterotrophic biological processes have been shown to exhibit different thermal sensitivities which can lead to increased grazing pressure and reduced primary producers standing biomass in aquatic systems (O'Connor et al, 2009).…”

Persistence of tri‐trophic interactions in seasonal environments

“…The majority of such interactions involves ectotherms (microbes, plants, invertebrates, fish, amphibians and reptiles) whose body temperature is directly affected by the environmental temperature. Increasing evidence of climate warming has spurred a body of theory on temperature effects on species interactions (Amarasekare & Coutinho, 2014; Amarasekare, 2015, 2019; Betini et al., 2019; Binzer et al., 2012; Dell et al., 2014; Gilbert et al., 2014; O'Connor et al., 2011; Ohlberger et al., 2011; Uszko et al., 2017; van de Wolfshaar et al., 2008; Vasseur & McCann, 2005). Much of this theory, however, focuses on pairwise interactions.…”