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

Abstract

Temperature has numerous effects on the structure and dynamics of ecological communities. Yet, there is no general trend or consensus on the magnitude and directions of these effects. To fill this gap, we propose a mechanistic framework based on key biological rates that predicts how temperature influences biomass distribution and trophic control in food webs. We show that these predictions arise from thermal mismatches between biological rates and across trophic levels. We couple our theory with experimental data for a wide range of species and find that warming should lead to top‐heavier terrestrial food chains and stronger top‐down control in aquatic environments. We then derive predictions for the effects of temperature on herbivory and validate them with data on stream grazers. Our study provides a mechanistic explanation of thermal effects on consumer–resource systems which is crucial to better understand the biogeography and the consequences of global warming on trophic dynamics.

Theory of temperature-dependent consumer-resource interactions

“…Even though biomass distributions and stability have been much studied properties of consumer-resource communities and food webs (Rall et al 2010(Rall et al , 2012Uszko et al 2017;Barbier & Loreau 2019;Bideault et al 2020), their predicted responses to warming vary.…”

“…On the other hand, we can aggregate groups of the primary parameters into fewer, biologically meaningful and empirically measurable quantities. The use of such aggregate parameters reduces the complexity of theoretical analyses, provides a mechanistic interpretation for the difference in predictions and facilitates the comparison among predictions (Barbier & Loreau 2019;Bideault et al 2020). Experimentally, replacing multiple measurements of individual parameters with measurements of the aggregates could also restrict the room for divergent findings.…”

“…Two community properties which describe important features of the community are consumer-resource biomass ratio and stability, defined with respect to the occurrence of oscillations. Their importance is reflected in their prevalence in the literature on the effects of warming on consumer-resource communities and food webs (Rall et al 2010, 2012; Uszko et al 2017; Barbier & Loreau 2019; Bideault et al 2020). However, predictions vary about the impacts of warming on both these community properties.…”

“…Experimentally, replacing multiple measurements of individual parameters with measurements of the aggregates could also restrict the room for divergent findings. Aggregate parameters have been utilised in theoretical studies already (Barbier & Loreau 2019; Bideault et al 2020). The seminal paper of Yodzis and Innes (1992) reduced the analysis of consumer-resource interactions to two principal aggregate parameters; consumer maximal energetic efficiency and a measure of resource abundance.…”

Flexible foraging behaviour increases predator vulnerability to climate change

“…Paradoxically, however, their ability to derive sound predictions for large communities under changing environmental conditionssupposed to be their main advantage over phenomenological forecasting models -has recently been challenged, stressing the need for more biological realism (Gauzens et al 2020, Sauve andBarraquand 2020). Indeed, a strong limitation of these models is that species are abstracted based on a set of biological rates that respond to temperature, such as metabolic or attack rates (Rall et al 2012, Gilbert et al 2014, Bideault et al 2021. Therefore, species responses to temperature are limited to the physiological part, whereas the behavioural component is ignored.…”