TPCs

Temperature is one of the most important environmental factors driving the genome-to-phenome relationship. Metabolic rates and related biological processes are predicted to increase with temperature due to the biophysical laws of chemical reactions. However, selection can also act on these processes across scales of biological organization, from individual enzymes to whole organisms. Although individual some studies have examined thermal responses across multiple scales, there is no general consensus on how these responses vary depending on the level of organization, or whether rates actually follow predicted theoretical patterns (e.g., Arrhenius-like exponential responses or thermal performance curves with showing peak responsess). Here, we performed a meta-analysis on studies where these rates were measured across the same set of temperatures, but at multiplethree levels of biological organization: enzyme activities, mitochondrial respiration, and/or whole-animal metabolic rates. Our final dataset consisted of 235 pairwise comparisons among between levels of organization from 13 publications. Thermal responses differed drastically across levels of biological organization, sometimes showing completely opposite patterns. We developed a new effect size metric, ‘organizational disagreement’, to quantify the difference in responses among levels of biological organization. Overall, rates at higher levels of biological organization (e.g., whole animal metabolic rates) increased more quickly with temperature than rates at lower levels, contrary to our predictions. Taxa and tissues examined generally did not affect organizational disagreement. Theoretical TPCs, where rates increase to a peak value and then drop, were only rarely observed (12%), while exponential increases following Arrhenius predictions were more common (29%). Our results suggest classic assumptions about thermal responses in biological rates are not supported by empirical datasets. Responses may differ across levels due to differing selection pressures or differing consequences of biochemical laws with increasing organization. TPCs may be rare because a broad range of test temperatures are rarely investigated (averaging only four test temperatures in our dataset). We advocate for more studies where thermal responses are measured across multiple levels of biological organization and for authors to explicitly address organizational disagreement in their interpretations. These results further emphasize the complexity of connecting the genome to the phenome when environmental plasticity is incorporated: the impact of the environment on the phenotype can depend on the scale of organization considered.<br>Here are the supplemental data associated with this project. They include:<br>File S1: All 235 pairwise comparisons of thermal responses used to calculate the organizational disagreement effect size metric.<br>File S2: The OD metric and its variance for each of the 235 comparisons.<br>File S3: The 189 thermal responses examined. <br>File S4: The R code used to perform the analyses and generate most of the figures.