Resource limitation determines realized thermal performance of consumers in trophodynamic models

Abstract

Recent work has demonstrated that changes in resource availability can alter a consumer's thermal performance curve (TPC). When resources decline, the optimal temperature and breadth of thermal performance also decline, leading to a greater risk of warming than predicted by static TPCs. We investigate the effect of temperature on coupled consumer‐resource dynamics, focusing on the potential for changes in the consumer TPC to alter extinction risk. Coupling consumer and resource dynamics generally reduces the potential for resource decline to exacerbate the effects of warming via changes to the TPC due to a reduction in top‐down control when consumers near the limits of their thermal performance curve. However, if resources are more sensitive to warming, consumer TPCs can be reshaped by declining resources, leading to increased extinction risk. Our work elucidates the role of top‐down and bottom‐up regulation in determining the extent to which changes in resource density alter consumer TPCs.

Mean species responses predict effects of environmental change on coexistence

“…A thermal mismatch refers to trophic levels having different temperature optima and/or thermal niches (Dell et al, 2014). Analyses have shown that such a mismatch will affect community dynamics and realised thermal niches (Amarasekare, 2015;Vinton & Vasseur, 2022). Our results show that, when the size of the feasibility domain is the response variable, such a mismatch will not consistently hamper or promote coexistence.…”

“…The identified communities are listed in Table S1; statistical results are in Table S2. Many analyses of environmental change effects on consumer-resource communities consider cases where a single resource feeds a single consumer, as this is a fundamental building block of more complex models (Amarasekare, 2015;Synodinos et al, 2021;Turschwell et al, 2022;Uszko et al, 2017;Vinton & Vasseur, 2022). In most of these cases, positive consumer density guarantees the feasibility of the species pair, as the consumer cannot persist without the resource.…”

Interactions between temperature and nutrients determine the population dynamics of primary producers

“…Despite the theoretical basis describing how a population's equilibrium (i.e. carrying capacity) ought to respond to multiple stressors (Vinton & Vasseur, 2022), population dynamics involve nonlinearities that make equilibrium behaviour just the starting point for forecasting responses to variable environments (Hastings et al, 2018). Under the rapid pace of global change, how populations will track changes in the mean and variance of the environment remains to be seen, as vital rates and underlying equilibria may be changing simultaneously.…”

“…Previous work has established that the optimum for thermal performance (here measured by the per-capita growth rate dB/Bdt) decreases under nutrient limitation due to the non-linearity of the two terms in Equation 9 (Thomas et al, 2017;Vinton & Vasseur, 2022). Under limiting nutrients, N cannot be factored out in the derivation of Equation ( 9) (though it retains the same general shape) and nutrient limitation therefore scales this curve.…”

“…where B is the population biomass density (volume −1 ; interchangeable with cell density since cell size is not considered in this model), and d(T ) is the temperature-dependent mortality rate (time −1 ). Previous work has shown that mortality rates scale as Boltzmann-Arrhenius relationships (Brown et al, 2004;Gillooly et al, 2001;McCoy & Gillooly, 2008); however, similar to other theoretical work (Amarasekare, 2015;Vinton & Vasseur, 2022), we represent mortality as an exponential function of temperature to increase model tractability without losing much accuracy over biologically relevant temperature ranges:…”