Scientists from Trinity College Dublin have unearthed a "universal thermal performance curve" (UTPC) that seemingly applies to all species and dictates their responses to temperature change. This UTPC essentially "shackles evolution" as no species seem to have broken free 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 well "species work" at different temperatures. And not only does the UTPC seem to apply to all species, but also to all measures of their performance with regard to temperature variation – whether you are measuring lizards running on a treadmill, sharks swimming in the ocean, or recording cell division rates in bacteria.
Crucially, the new UTPC shows that as all organisms warm:
- performance slowly increases until they reach an optimum (where performance is greatest),
- but then with further warming performance quickly declines.
- The rapid decline above optimum temperatures means overheating can be dangerous, risking physiological failure or even death.
One obvious takeaway from the work, just published in leading international journal PNAS, is that species may be more constrained than feared when it comes to their ability to adapt to global climate change, given that in most places temperatures are rising.
Andrew Jackson, Professor in Zoology in Trinity's School of Natural Sciences, and co-author, said: "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 5oC to 100oC, and their performance can vary a lot depending on the measure of performance being observed and the species in question."
"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."
"Whatever the species, it simply must have a smaller temperature range at which life is viable once temperatures shift above the optimum."
Senior author, Dr Nicholas Payne, from Trinity's School of Natural Sciences, added: "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."
"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."
"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."
