Thermal performance curves have provided a common framework to study the impact of temperature in biological systems. However, few generalities have emerged to date. Here we combine an experimental approach with theoretical analyses to demonstrate that performance curves are expected to vary predictably with the levels of biological organization. We measured rates of enzymatic reactions, organismal performance and population viability in Drosophila acclimated to different thermal conditions and show that performance curves become narrower with thermal optima shifting towards lower temperatures at higher levels or organization. We then explain these results on theoretical grounds, showing that this pattern reflects the cumulative impact of asymmetric thermal effects that piles up with complexity. These results and the proposed framework are important to understand how organisms, populations and ecological communities might respond to changing thermal conditions.

Outbred Drosophila stocks were maintained for five generations in the laboratory, and flies from these stocks were then separated into four different temperature acclimation treatments. Individuals were randomly sampled and employed in measurements of hexokinase specific enzymatic activity, whole-organismal metabolic rate, maximum running speed and viability. All measurements encompass males and females from the same generation, and specific details regarding the procedures to estimate these variables are available in the original paper.  

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