The “universal thermal performance curve” that hinders evolution

Scientists from Trinity College Dublin have discovered a universal thermal performance curve (UTPC) that appears to apply to all species and dictates their responses to temperature changes. This UTPC essentially hinders evolution, because no species appears to have freed itself from the constraints it imposes on how temperature affects performance.

All living things are affected by temperature, but the newly discovered UTPC unifies tens of thousands of seemingly different curves that explain how species function at different temperatures. And not only does UTPC seem to apply to all species, but also to all measures of their performance in temperature variation – whether measuring lizards running on a treadmill, sharks swimming in the ocean, or recording the cell division rates of bacteria.

Basically, the new UTPC shows that as all organisms warm, their performance slowly increases until they reach an optimum (where performance is highest), but then with further warming, performance declines rapidly.

The rapid drop in optimal temperatures means overheating can be dangerous, risking physiological failure or even death.

An obvious point to remember from the work, published in PNASis that species may be more constrained than previously thought in their ability to adapt to global climate change, given that temperatures are increasing in most places.

Andrew Jackson, professor of zoology at Trinity’s School of Natural Sciences and co-author, said: “Across thousands of species and almost every group 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 significantly depending on temperature. on the measurement of observed performance and on the species in question.

“This has led to countless model variations being proposed to explain these differences. What we have shown here is that all the different curves are in fact exactly the same 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.”

“Whatever the species is, it simply must have a smaller temperature range at which life is viable once temperatures rise above the optimum.”

Lead author Dr Nicholas Payne, from Trinity’s School of Natural Sciences, added: “These results come from an extensive analysis of more than 2,500 different thermal performance curves, which include a wide variety of different performance measures for an equally wide variety of different species, from bacteria to plants, and from lizards to insects.”

“This means the trend holds for species in all major groups that have diverged massively as the tree of life has expanded over billions of years of evolution.

“Despite this rich diversity of life, our study shows that fundamentally all life forms remain remarkably constrained by this ‘rule’ about how temperature influences their ability to function. The best evolution we have managed to make is to shift this curve – life has not found a way to deviate from this very specific form of thermal performance.”

“The next step is to use this model as a sort of benchmark to see if we can find any species or systems that might, subtly, deviate from this pattern. If we find any, we’ll be happy to ask why and how they do so, especially given predictions about how our climate is likely to continue to warm over the coming decades.”