Consistent temperature dependence of functional response parameters and their use in predicting population abundance

Laura Prugh,Louise C Archer,Rebecca L Kordas,Eoin J O’Gorman,Bruno Gallo,Björn C Rall,Esra H Sohlström,Guy Woodward,Malte Jochum

doi:10.1111/1365-2656.13060

Abstract

Global warming is one of the greatest threats to the persistence of populations: increased metabolic demands should strengthen pairwise species interactions, which could destabilize food webs at the higher organizational levels. Quantifying the temperature dependence of consumer–resource interactions is thus essential for predicting ecological responses to warming.We explored feeding interactions between different predator–prey pairs in controlled‐temperature chambers and in a system of naturally heated streams. We found consistent temperature dependence of attack rates across experimental settings, though the magnitude and activation energy of attack rate were specific to each predator, which varied in mobility and foraging mode.We used these parameters along with metabolic rate measurements to estimate energetic efficiency and population abundance with warming. Energetic efficiency accurately estimated field abundance of a mobile predator that struggled to meet its metabolic demands, but was a poor predictor for a sedentary predator that operated well below its energetic limits. Temperature effects on population abundance may thus be strongly dependent on whether organisms are regulated by their own energy intake or interspecific interactions.Given the widespread use of functional response parameters in ecological modelling, reconciling outcomes from laboratory and field studies increases the confidence and precision with which we can predict warming impacts on natural systems.

Highlights

Global warming is widely predicted to increase the metabolic demands of organisms (Brown, Gillooly, Allen, Savage, & West, 2004; Gilbert et al, 2014), which could strengthen short‐term consumer–resource interactions (O'Connor, 2009; Rall, Vucic‐Pestic, Ehnes, Emmerson, & Brose, 2010) and potentially destabilize ecological communities via cascading food web effects (Allesina & Tang, 2012; O'Gorman & Emmerson, 2009)
Limnophora riparia was absent from the coldest streams in the system, and its population abundance increased with increasing temperature (GAMM: F = 12.36, p = .001; r2 = .17; Figure 3a)
We have demonstrated consistency in the temperature dependence of functional response parameters across field and laboratory settings, which supports their use in predictive modelling for estimating warming effects on natural systems (Binzer et al, 2016; Fussmann et al, 2014; Petchey et al, 2010; Vasseur & McCann, 2005)

Summary

| INTRODUCTION

Global warming is widely predicted to increase the metabolic demands of organisms (Brown, Gillooly, Allen, Savage, & West, 2004; Gilbert et al, 2014), which could strengthen short‐term consumer–resource interactions (O'Connor, 2009; Rall, Vucic‐Pestic, Ehnes, Emmerson, & Brose, 2010) and potentially destabilize ecological communities via cascading food web effects (Allesina & Tang, 2012; O'Gorman & Emmerson, 2009). Attack rates typically increase and handling times decrease with warming in functional response experiments, at least up to a thermal optimum of the consumer (Englund et al, 2011; Rall et al, 2012) This could strengthen top‐down control in warmer environments, suppressing the abundance of resource species and potentially even driving them locally extinct (Vasseur & McCann, 2005). Since the temperature dependences of functional response parameters influence higher organizational levels, they are increasingly used in models to predict how populations and food webs will change with warming (Binzer, Guill, Rall, & Brose, 2016; Fussmann et al, 2014; Gilbert et al, 2014; Osmond et al, 2017; Petchey, Brose, & Rall, 2010; Vasseur & McCann, 2005) This signals a move beyond climate envelope approaches that ignore biotic interactions and are not mechanistic (Araújo & Luoto, 2007). We tested the utility of these parameters for (3) predicting changes in population abundance and persistence of two consumers with contrasting species traits in response to increasing temperature, highlighting how they may be embedded in the mechanistic and predictive study of biotic responses to warming

| MATERIALS AND METHODS

| DISCUSSION

Findings

| CONCLUSIONS