Abstract
AbstractAlthough 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.
Highlights
Temperature is perhaps the most widely recognized environmental factor driving ecological processes today
If the thermal optimum of the densityindependent growth rate of the resource is at higher temperature than the feeding rate parameters for the consumer, increases in temperature should weaken the demographic effect of consumption because the resource would perform better at higher temperature. We investigated this hypothesis on the non-motile green algae Chlorella vulgaris and the freshwater water flea Daphnia magna living in 26,000 L freshwater mesocosms
Model development To evaluate the potential effects of temperature-dependent traits on consumer–resource dynamics, we developed a model in which the intrinsic growth rate of the resource r (T), the attack rate a (T), and the handling time h (T) by the consumer were all independent parabolic functions of ambient temperature, with potentially different thermal optima
Summary
Temperature is perhaps the most widely recognized environmental factor driving ecological processes today. Recent theoretical work suggests that the unimodal response to temperature of physiological traits could scale up to affect higher order processes, such as species interaction, leading to a similar unimodal change in interaction strength (Amarasekare 2015, Uszko et al 2017, Bideault et al 2019) This could happen because thermal performance curves, which are determined by metabolic rate, are often a dome-shaped function of ambient temperature (Brown et al 2004, Savage et al 2004, Sibly et al 2012). Description rmax constant, Eq 1 rmax constant, Eq 1 rmax constant, Eq 1 Attack rate and handling time constant, Eqs. 2 and 3 Attack rate and handling time constant, Eqs. 2 and 3 Attack rate and handling time constant, Eq 2 Handling time constant, Eq 3 Temperature
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