Abstract
Global warming over the next century is likely to alter the energy demands of consumers and thus the strengths of their interactions with their resources. The subsequent cascading effects on population biomasses could have profound effects on food web stability. One key mechanism by which organisms can cope with a changing environment is phenotypic plasticity, such as acclimation to warmer conditions through reversible changes in their physiology. Here, we measured metabolic rates and functional responses in laboratory experiments for a widespread predator-prey pair of freshwater invertebrates, sampled from across a natural stream temperature gradient in Iceland (4-18℃). This enabled us to parameterize a Rosenzweig-MacArthur population dynamical model to study the effect of thermal acclimation on the persistence of the predator-prey pairs in response to warming. Acclimation to higher temperatures either had neutral effects or reduced the thermal sensitivity of both metabolic and feeding rates for the predator, increasing its energetic efficiency. This resulted in greater stability of population dynamics, as acclimation to higher temperatures increased the biomass of both predator and prey populations with warming. These findings indicate that phenotypic plasticity can act as a buffer against the impacts of environmental warming. As a consequence, predator-prey interactions between ectotherms may be less sensitive to future warming than previously expected, but this requires further investigation across a broader range of interacting species.
Highlights
The average global surface temperature is on course to rise by at least 1.5°C above pre-industrial levels in the coming decades (Masson-Delmotte et al, 2018)
We found that thermal acclimation reduced the attack coefficient of L. riparia feeding on Simuliidae prey, leading to lower feeding rates in warmer environments, but still greatly exceeding the predator's metabolic demand
Factors that determine interaction strength such as metabolic rates and attack coefficients have been shown to scale predictably with environmental temperature (Brown et al, 2004; Englund et al, 2011; Rall et al, 2012; Vucic-Pestic et al, 2011). Consistent with these expectations, we found that the metabolic rate, attack coefficient, and overall feeding rate of the predatory L. riparia increased with experimental warming
Summary
The average global surface temperature is on course to rise by at least 1.5°C above pre-industrial levels in the coming decades (Masson-Delmotte et al, 2018). Warming should alter the physiology of individuals, with the rate of energy and material uptake, transformation, and expenditure (i.e. metabolic rate) shown to increase exponentially up to the thermal optimum of the organism (Brown et al, 2004; Kordas et al, 2011). This could have direct effects on population biomasses and indirect effects through changes in the strength of predator–prey interactions, with consequences for community structure and food web stability (Emmerson et al, 2004; Fussmann et al, 2014; Rall et al, 2010). It is crucial to understand how warming alters both metabolic demand and the strength of interactions between consumers and resources, to predict how future warming might alter community structure and food web stability
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