Temperature alters the shape of predator–prey cycles through effects on underlying mechanisms

Abstract

Background Predicting the effects of climate warming on the dynamics of ecological systems requires understanding how temperature influences birth rates, death rates and the strength of species interactions. The temperature dependance of these processes—which are the underlying mechanisms of ecological dynamics—is often thought to be exponential or unimodal, generally supported by short-term experiments. However, ecological dynamics unfold over many generations. Our goal was to empirically document shifts in predator–prey cycles over the full range of temperatures that can possibly support a predator–prey system and then to uncover the effect of temperature on the underlying mechanisms driving those changes. Methods We measured the population dynamics of the Didinium-Paramecium predator–prey system across a wide range of temperatures to reveal systematic changes in the dynamics of the system. We then used ordinary differential equation fitting to estimate parameters of a model describing the dynamics, and used these estimates to assess the long-term temperature dependance of all the underlying mechanisms. Results We found that predator–prey cycles shrank in state space from colder to hotter temperatures and that both cycle period and amplitude varied with temperature. Model parameters showed mostly unimodal responses to temperature, with one parameter (predator mortality) increasing monotonically with temperature and one parameter (predator conversion efficiency) invariant with temperature. Our results indicate that temperature can have profound, systematic effects on ecological dynamics, and these can arise through diverse and simultaneous changes in multiple underlying mechanisms. Predicting the effects of temperature on ecological dynamics may require additional investigation into how the underlying drivers of population dynamics respond to temperature beyond a short-term, acute response.

Implications of increasing temperature stress for predatory biocontrol of vector mosquitoes

“…coevolved predator-prey and host-natural enemy association under high temperature stress [ 34 , 35 ]. It is nevertheless critical to directly investigate and establish predator-prey interaction dynamics under varied temperatures [ 90 , 91 ] and how optimal performance may relate to CTLs. This will allow for a more effective assessment of constraints of biological control associated with thermal stress prior to organismal loss of physiological function, e.g.…”

Predation by protists influences the temperature response of microbial communities

“…The strength of feeding interactions, in particular, increases with temperature, as feeding rates increase among consumers to compensate for increasing metabolic demands (Dell et al, 2011;Gillooly et al, 2001). Stronger predation in turn leads to declines in prey abundance and total biomass (Barneche et al, 2021;DeLong & Lyon, 2020;Garzke et al, 2019;Gilbert et al, 2014). Because gross respiration rates are determined by standing biomass, temperature effects on predation may ultimately influence ecosystem-level processes such as community respiration rates (O'Connor et al, 2009), and thus mediate the temperature response of microbial respiration rates worldwide.…”

“…However, with a global biomass 200 times larger than that of nematodes (Bar-On et al, 2018), unicellular eukaryotes -collectively known as 'protists' -likely play a major role in regulating microbial communities at global scales (Oliverio et al, 2020) through bacterivory (Erktan et al, 2020;Gao et al, 2019). Ciliate protists, in particular, are wellknown bacterivores (Foissner & Berger, 1996), their population dynamics and feeding interactions are strongly temperature-dependent (DeLong & Lyon, 2020), and they are present in all major ecosystems (Foissner & Berger, 1996;Oliverio et al, 2020). As such, predation of microorganisms by protists can mediate the temperature response of microbial communities (Gao et al, 2019;Geisen et al, 2021), although this phenomenon has only been shown for one species of protist in soils (Geisen et al, 2021).…”

“…If general, this process has the potential to strongly influence microbial respiration worldwide under warmer temperatures (Crowther et al, 2015;Geisen et al, 2018). Additionally, microbial predators respond to environmental conditions themselves in multiple ways, including changes in feeding rates (DeLong & Lyon, 2020;Englund et al, 2011) and changes in the traits that influence predation (Atkinson et al, 2003;Dell et al, 2011;Gibert et al, 2016), which add complexity to an already complex problem.…”

Estimating predator functional responses using the times between prey captures

“…For example, Kalinkat et al (2013) examined the effects of predator and prey body sizes on the functional response across 25 different predator species feeding on eight differently sized prey species requiring 2,564 experimental units. Finally, foraging rates depend on both abiotic and biotic conditions (Abrams & Ginzburg, 2000;Gilbert et al, 2014;Preston et al, 2018;DeLong & Lyon, 2020), so identifying the way in which temperature, predator density, or habitat complexity, for example, influence the functional response generates the same level of replication challenge.…”