Figure 1.

The relationship of growth rate ($r_{\max }$) with temperature in ectotherms (the thermal performance curve; TPC). The TPC is generally unimodal and asymmetric, here quantified by the four‐parameter Sharpe‐Schoolfield model (black line; Schoolfield et al. 1981) fitted to growth rate measurements of the dinoflagellate Amphidinium klebsii (Morton et al. 1992). The parameters of the model are B ₀ (in units of s⁻¹), E (eV), $T_{\text{pk}}$ (K), and $E_{\mathrm{D}}$ (eV). B ₀ is the growth rate at a reference temperature below the peak ($T_{\text{ref}}$) and controls the vertical offset of the TPC. E sets the rate at which the curve rises and is, therefore, a measure of thermal sensitivity at the operational temperature range. $T_{\text{pk}}$ is the temperature at which growth rate is maximal, and $E_{\mathrm{D}}$ controls the fall of the curve. Two other parameters control the shape of the curve and can be calculated from the four main parameters: $B_{\text{pk}}$ (s⁻¹); the maximum height of the curve, and $W_{\text{op}}$ (K); the operational niche width, which we define as the difference between $T_{\text{pk}}$ and the temperature at the rise of the curve where growth rate is half of $B_{\text{pk}}$. Further information regarding the assumptions of the model are provided in the section “Estimation of TPC parameter values” of the Methods.