Temperature variability alters the stability and thresholds for collapse of interacting species

Abstract

18Temperature variability and extremes can have profound impacts on populations and ecological 19 communities. Predicting impacts of thermal variability poses a challenge because it has both 20 direct physiological effects and indirect effects through species interactions. In addition, 21 differences in thermal performance between predators and prey and non-linear averaging of 22 temperature-dependent performance can result in complex and counterintuitive population 23 2 dynamics in response to climate change. Yet the combined consequences of these effects remain 24 underexplored. Here, modeling temperature-dependent predator-prey dynamics, we study how 25 changes in temperature variability affect population size, collapse, and stable coexistence of both 26 predator and prey, relative to under constant environments or warming alone. We find that the 27 effects of temperature variation on interacting species can lead to a diversity of outcomes, from 28 predator collapse to stable coexistence, depending on interaction strengths and differences in 29 species' thermal performance. Temperature variability also alters predictions about population 30 collapse -in some cases allowing predators to persist for longer than predicted when considering 31 warming alone, and in others accelerating collapse. To inform management responses that are 32 robust to future climates with increasing temperature variability and extremes, we need to 33 incorporate the consequences of temperature variation in complex ecosystems. 34 35 a greater risk to species than increases in mean temperature [7,8,11], predicting the importance 47 of temperature variability and extremes for populations, communities, and the ecosystem 48 functions and services they support remains challenging. First, temperature can have both direct 49 and indirect effects that create complex feedbacks and dynamics [12]. Directly, temperature 50 affects species through physiological performance. But temperature can also impact species 51 indirectly, as shown for warming [13,14], by increasing or decreasing important resources or 52 prey species (in turn affecting consumers and predators), changing competitive abilities (altering 53 prey abundance distributions), and altering feeding rates and top-down control (affecting prey) 54 [15][16][17][18]. Second, even without shifts in mean temperatures, temperature variability can alter 55 mean vital rates because of non-linear relationships between temperature and processes including 56 growth, reproduction, and mortality (Fig 1; [19]). As a result, the responses of populations to 57 increasing temperature variability and extremes induced by climate change, especially in a 58 community context, remains a key research frontier in marine population dynamics, community 59 ecology, and fisheries science. 60Directly, temperature variability can impact populations of species in a variety of ways, 61including by altering the rates of fundamental processes that determine population size, 62 extinction risk, and productivity. Increases i...

Benthic estuarine communities' contribution to bioturbation under the experimental effect of marine heatwaves

“…No doubt, heatwaves are increasing and may present different and unpredictable characteristics 1 , 19 . This study highlights the importance of studying temperature variability over average temperature changes 5 and understanding its extremes' impact regarding duration and severity, seasonal timing, and frequency (incl. recurrence and diurnal variability 37 ), in line with predictions 1 , 2 , 19 .…”

“…Due to their nature, heatwaves are extreme climate events, as they represent sudden and abnormal temperature increases that may last from 5 consecutive days to even months 4 . Marine ecosystems are particularly vulnerable to heatwaves, with documented impacts that range from species physiology aspects 5 – 7 to broader consequences at communities 8 – 10 and ecosystem-level 2 , 9 , 11 , with severe economic implications 12 , 13 .…”

Synthesising the multiple impacts of climatic variability on community responses to climate change

“…Although to date the number of examples is small, it is clear that climate-driven shifts in variability patterns could play a role in determining coexistence between competitors and range limits in the future. While we have focussed here on competitive systems, consumer-resource systems can be analysed in parallel ways (Dee et al 2020;Shoemaker et al 2020a). However, effects identified in simple communities may not necessarily directly translate to more complex systems (Barabás et al 2018, Song et al 2019.…”

“…However, temporal variability influences species dynamics, and hence response to climate change through multiple direct and indirect routes (Fig 1. ) We propose here that the current discussion around ecological responses to climate change could be missing a key element -the role of temporal variability in determining how interspecific interactions play out (Vasseur & Fox 2009;Gudmundson et al 2015;Fey & Vasseur 2016;Dee et al 2020). Two related questions emerge: firstly, how does considering variability change our expectations for how communities will respond to shifts in mean conditions?…”

Theory of temperature-dependent consumer-resource interactions

“…However, the thermal response curves of resource growth rate, r , attack rate, a , and handling time, h , have been represented either through the Arrhenius equation (Vasseur & McCann 2005; Binzer et al 2016) or as unimodal functions (Amarasekare 2015; Uszko et al 2017; Zhang et al 2017; Uiterwaal & DeLong 2020; Zhao et al 2020). Carrying capacity, K , and consumer assimilation efficiency, e , have a less clear connection to temperature (Uszko et al 2017; Dee et al 2020). We selected two parametrisations related to the ongoing debate surrounding the importance of including the decreasing part of the biological rates beyond the optimal temperature (Pawar et al 2016) and used these as an illustrative comparison.…”