Researchers at Trinity College in Dublin report the discovery of what they believe to be a “universal thermal performance curve” (UTPC) that applies to the entire tree of life. The researchers say this pattern determines how organisms respond to changes in temperature. The results of this study suggest that this rule is effectively an “evolutionary shackle.” This is because the species studied so far have not been able to escape the limitations this regulation imposes on the effects of temperature on biological performance.
Temperature affects all living things. The newly described UTPC brings together tens of thousands of previously individual performance curves that scientists have used to understand how well different species perform at different temperatures. The researchers found that these curves all follow the same underlying pattern. This applies not only between species but also to many different types of biological activity. This pattern holds true whether scientists are testing how fast a lizard runs on a treadmill, measuring how a shark swims in the ocean, or tracking the rate at which bacterial cells divide.
General patterns of how life responds to heat
UTPC reveals a consistent relationship between temperature and performance in organisms. As temperature increases, biological performance typically increases gradually until an optimum point (maximum performance) is reached.
However, once the temperature exceeds this optimum, performance degrades rapidly. This rapid drop at high temperatures means overheating can quickly become dangerous and lead to physiological deterioration and death.
Research published in journals PNASsuggests that species may face stronger constraints in adapting to climate change than previously thought. As temperatures rise across much of the Earth, these constraints may affect how well organisms can cope with future warming.
One curve shared throughout the tree of life
Andrew Jackson, professor of zoology at Trinity University’s School of Natural Sciences and co-author of the study, explained that the study revealed surprising similarities between many life forms.
“Across thousands of species and nearly all groups of organisms, including bacteria, plants, reptiles, fish, and insects, the shape of the curve that describes the change in performance with temperature is very similar. However, the optimal temperature for different species varies widely, ranging from 5°C to 100°C, and performance varies widely depending on the performance measure observed and the species in question.”
Scientists have developed many models to explain the wide range of temperature responses found in nature. But new research shows that these differences are changes in the same basic curve.
“This has led to countless variations of models that have been proposed to explain these differences. What we have shown here is that the different curves are all actually the same exact curve, just stretched or shifted at different temperatures. Furthermore, we have shown that the optimal temperature and the critical maximum temperature at which mortality occurs are closely related.”
Jackson also noted that when temperatures exceed the optimum, the range in which organisms can survive becomes narrower.
“Whatever the species, there has to be a narrow temperature range in which life can survive when temperatures exceed the optimum.”
Research analyzing thousands of thermal performance curves
Lead author Dr Nicholas Payne, from Trinity School of Natural Sciences, said the conclusions were based on an extensive data set.
“These results came from a detailed analysis of more than 2,500 different thermal performance curves, which contain a huge variety of performance measurements for an equally vast variety of different species, from bacteria to plants, lizards to insects.”
The results show that this common pattern appears in nearly every major field of life that has evolved over billions of years.
“This means that the pattern holds true for all major groups of species, where the tree of life has diverged significantly over billions of years of evolution. Despite this rich diversity of life, our research shows that essentially all life forms remain severely constrained by this ‘law’ of how temperature affects their ability to function.” The best way evolution has succeeded is to shift this curve. Life has not found a way to deviate from this very specific thermal performance shape. ”
Find exceptions to rules
The researchers now plan to use the UTPC as a reference point to investigate whether there are organisms that slightly deviate from this pattern.
“The next step is to use this model as a kind of benchmark to see if we find species or systems that might subtly break away from this pattern. If we do, we’re excited to ask why and how, especially given projections of how our climate is likely to continue warming in the coming decades.”
