Researchers at Trinity College Dublin report that they have discovered a “universal thermal performance curve” (UTPC) that applies to the entire tree of life. According to the team, this pattern controls how organisms respond to changes in temperature. The findings suggest that this rule effectively “freezes evolution”, as no species studied so far has managed to escape the limits that govern how temperature affects biological performance.
Temperature affects every living organism. The newly described UTPC brings together thousands of previously isolated performance curves that scientists have used to understand how well different species perform at different temperatures. The researchers found that all of these curves follow the same underlying pattern. This applies not only to species, but also to many different types of biological activities. This pattern shows up whether scientists are testing how fast lizards run on a treadmill, measuring how sharks swim in the ocean, or tracking how fast bacterial cells divide.
A general pattern of how life reacts to heat
UTPC reveals a consistent relationship between temperature and performance in living organisms. As temperature increases, biological performance generally gradually improves until an optimal point (where performance is greatest) is reached.
However, once the temperature rises beyond this optimum, performance degrades rapidly. This drastic drop at high temperatures means that overheating can quickly become dangerous, potentially leading to physical disintegration or even death.
Study, published in journal PNASSuggests that species may face stronger limits than previously thought when it comes to adapting to climate change. With temperatures rising across much of the planet, these constraints could affect how well organisms can cope with future warming.
A curve shared on the tree of life
Andrew Jackson, professor of zoology at Trinity School of Natural Sciences and co-author of the study, said the research revealed surprising similarities across many forms of life.
“Across thousands of species and nearly all groups of life, including bacteria, plants, reptiles, fishes, and insects, the shape of the curve that describes how performance changes with temperature is very similar. However, different species have very different optimum temperatures, from 5°C to 100°C, and their performance can vary greatly depending on the performance measure being observed and the species involved.”
Scientists have previously developed several models to explain the wide range of temperature responses observed in nature. However, new research indicates that these differences are variations of the same basic curve.
“This has led to countless variations in models being proposed to explain these differences. What we have shown here is that all the different curves are actually the same exact curve, just stretched and shifted at 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 of survival of organisms narrows.
“Whatever the species, it simply must have a small temperature range over which life can be viable if temperatures go above the optimum.”
Thousands of thermal performance curves were analyzed in the study
Senior author Dr Nicholas Payne, from Trinity School of Natural Sciences, said the findings are based on a comprehensive dataset.
“These results emerge from a thorough analysis of over 2,500 different thermal performance curves, covering a tremendous variety of different performance measures for an equally tremendous diversity of species, from bacteria to plants, and from lizards to insects.”
The results show that this shared pattern appears in almost every major branch of life that has evolved over billions of years.
“This means that the pattern applies to species in all major groups, which have diverged extensively as the tree of life has grown over billions of years of evolution. Despite this rich diversity of life, our study shows that basically all life forms remain remarkably constrained by this ‘rule’ for how temperature affects their ability to function. The best evolution has managed to do is move around this curve – with no way for life to deviate from this specific thermal performance shape.” Got it.”
Finding exceptions to the rule
The researchers now plan to use the UTPC as a reference point to investigate whether any organisms might deviate slightly from this pattern.
“The next step is to use this model as a benchmark to see if there are any species or systems we might find that might subtly deviate from this pattern. If we find any, we’ll be excited to ask why and how they do so – especially given predictions of how warm our climate is likely to be over the next decades.”
