Researchers at Trinity College Dublin report that they have uncovered what appears to be a “universal thermal performance curve” (UTPC) that applies across the entire tree of life. According to the team, this pattern governs how organisms respond to changes in temperature. The findings suggest that this rule effectively “shackles evolution,” because no species studied so far has managed to escape the limits it places on how temperature influences biological performance.
Temperature affects every living organism. The newly described UTPC brings together tens of thousands of previously separate performance curves that scientists have used to understand how well different species function at various temperatures. The researchers found that these curves all follow the same underlying pattern. This applies not only across species, but also across many different types of biological activity. The pattern holds whether scientists are testing how fast lizards run on a treadmill, measuring how sharks swim in the ocean, or tracking how quickly bacterial cells divide.
A Common Pattern in How Life Responds to Heat
The UTPC reveals a consistent relationship between temperature and performance in living organisms. As temperatures rise, biological performance generally improves gradually until reaching an optimal point (where performance is greatest).
Once temperatures move beyond this optimum, however, performance declines rapidly. This steep drop at higher temperatures means that overheating can quickly become dangerous, potentially causing physiological breakdown or even death.
The study, published in the journal PNAS, suggests that species may face stronger limits than previously thought when it comes to adapting to climate change. With temperatures increasing across much of the planet, these constraints could affect how well organisms can cope with future warming.
One Curve Shared Across the Tree of Life
Andrew Jackson, Professor in Zoology in Trinity’s School of Natural Sciences and a co author of the study, explained that the research uncovered striking similarities across many forms of life.
“Across thousands of species and almost all groups of life including bacteria, plants, reptiles, fish and insects, the shape of the curve that describes how performance changes with temperature is very similar. However, different species have very different optimal temperatures, ranging from 5°C to 100°C, and their performance can vary a lot depending on the measure of performance being observed and the species in question.”
Scientists have previously developed many models to explain the wide range of temperature responses seen in nature. However, the new research indicates that these differences are variations of the same basic curve.
“That has led to countless variations on models being proposed to explain these differences. What we have shown here is that all the different curves are in fact the same exact curve, just stretched and shifted over different temperatures. And what’s more, we have shown that the optimal temperature and the critical maximum temperature at which death occurs are inextricably linked.”
Jackson also noted that once temperatures rise above the optimum, the range in which organisms can survive becomes narrower.
“Whatever the species, it simply must have a smaller temperature range at which life is viable once temperatures shift above the optimum.”
Study Analyzed Thousands of Thermal Performance Curves
Senior author Dr. Nicholas Payne from Trinity’s School of Natural Sciences said the conclusions are based on an extensive dataset.
“These results have sprung forward from an in-depth analysis of over 2,500 different thermal performance curves, which comprise a tremendous variety of different performance measures for a similarly tremendous variety of different species — from bacteria to plants, and from lizards to insects.”
The results indicate that this shared pattern appears across nearly every major branch of life that has evolved over billions of years.
“This means the pattern holds for species in all major groups that have diverged massively as the tree of life has grown throughout billions of years of evolution. Despite this rich diversity of life, our study shows basically all life forms remain remarkably constrained by this ‘rule’ on how temperature influences their ability to function. The best evolution has managed is to move this curve around — life hasn’t found a way to deviate from this one very specific thermal performance shape.”
Searching for Exceptions to the Rule
The researchers now plan to use the UTPC as a reference point to investigate whether any organisms might slightly break away from this pattern.
“The next step is to use this model as something of a benchmark to see if there are any species or systems we can find that may, subtly, break away from this pattern. If we find any, we will be excited to ask why and how they do it — especially given forecasts of how our climate is likely to keep warming in the next decades.”