A viewpoint on ecological and evolutionary study of plant thermal performance curves in a warming world

Abstract

We can understand the ecology and evolution of plant thermal niches through thermal performance curves (TPCs), which are unimodal, continuous reaction norms of performance across a temperature gradient. Though there are numerous plant TPC studies, plants remain underrepresented in syntheses of TPCs. Further, few studies quantify plant TPCs from fitness-based measurements (i.e., growth, survival, and reproduction at the individual level and above), limiting our ability to draw conclusions from the existing literature about plant thermal adaptation. We describe recent plant studies that use a fitness-based TPC approach to test fundamental ecological and evolutionary hypotheses, some of which have uncovered key drivers of climate change responses. Then, we outline three conceptual questions in ecology and evolutionary biology for future plant TPC studies: 1) Do populations and species harbor genetic variation for TPCs? 2) Do plant TPCs exhibit plastic responses to abiotic and biotic factors? 3) Do fitness-based TPCs scale up to population-level thermal niches? Moving forward, plant ecologists and evolutionary biologists can capitalize on TPCs to understand how plasticity and adaptation will influence plant responses to climate change.

Tree biodiversity of warm drylands is likely to decline in a drier world

“…Following the IPCC 2022 conceptual framework for risk assessment (Pörtner et al, 2022), the risk of decline of tree taxa was inferred by comparing species aridity niches and range size, reflecting vulnerability, with predicted aridity changes, reflecting exposure. Our methodology to quantify exposure and vulnerability is based on density of occurrences curves across the aridity gradient (Figure 1) and has been previously used to estimate species responses to climate change (Peng et al, 2021; Wooliver et al, 2022). It has been demonstrated that niche metrics as well as range size are crucial to estimate vulnerability to climate change (Thuiller et al, 2005).…”

Application of the thermal death time model in predicting thermal damage accumulation in plants

“…Both static and dynamic ramping assays are used to generate estimates of the upper and/or lower thermal limits of species (O'sullivan et al, 2017;Lancaster & Humphreys, 2020;Geange et al, 2021;Wooliver et al, 2022), for example through thermal performance curves (TPCs) which do not take both the intensity and the duration of the stress into account (Rezende & Bozinovic, 2019;O'sullivan et al, 2017). Without taking exposure duration into account, thermal tolerance estimates may be derived from both the permissive and stressful temperature range.…”

“…Thermal tolerance in plants is often assessed through controlled ramping or static assays and is usually estimated in relation to stress intensity (e.g. upper and lower thermal tolerance limits and Thermal Performance Curves (TPCs)) (O’sullivan et al, 2013; Curtis et al, 2014; O’sullivan et al, 2017; Zhu et al, 2018; Lancaster & Humphreys, 2020; Sentinella et al, 2020; Geange et al, 2021; Wooliver et al, 2022). Across studies, stress durations can vary from anywhere between minutes to weeks and is sometimes considered negligible or simply dictated by the chosen stress assay type.…”

Mutualisms in a warming world

“…Thermal performance curves (TPCs) are well‐recognized to provide a rigorous, mechanistic, physiology‐based approach for understanding how species' traits respond to current and future thermal regimes (Buckley et al, 2022; Sinclair et al, 2016; Wooliver et al, 2022). Typically, these curves characterize average thermal responses (performance) of individual species' traits across a thermal gradient.…”

“…In this example, Site 1 (S 1 ) yields lower mutualism performance (MTPA) relative to Site 2 (S 2 ) due to reduced overlap (MTPC) in trait a . This prediction is derived from empirical evidence for variation in the thermal tolerance found throughout species' ranges, for example, rain shadow effects that alter thermal tolerance in ant populations (Baudier & O'Donnell, 2020), as well as predictable differences in thermal tolerance between individual‐ and population‐level performance metrics, for example, metabolic rate, movement and components of fitness (Bozinovic et al, 2020; Wooliver et al, 2022). These thermal response differences are the result of interactive effects between thermal heterogeneity within an environment and the biological scale of benefit trait performance (e.g.…”