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How do organisms adapt to climate change? A new study reveals the complex interplay between genetic diversity and temperature tolerance evolution.

The maintenance of biodiversity crucially depends on the evolutionary potential of populations to adapt to environmental change. Accelerating climate change and extreme temperature events urge us to better understand and forecast evolutionary responses.

In the study, in the Proceedings of the National Academy of Sciences, researchers at Stockholm University harnessed the power of experimental evolution with the microbial model system yeast (Saccharomyces spp.) to measure the evolutionary potential of populations to adapt to future warming, in real time and across the entire species tree.

No single way to adapt to climate change

The researchers tracked the evolution of thermal performance curves (TPCs) in populations of eight genetically and ecologically diverse species of yeast (baker's yeast and its relatives) from all over the world. They used gradually increasing temperature conditions, from 25掳C to 40掳C, to simulate global warming for more than 600 generations of yeast.

The study reveals that adaptive responses to climate change are highly species-specific and highlights the complex interplay between genetic diversity and temperature tolerance evolution. These findings stress the importance of accounting for both inter- and intraspecies genetic variation when forecasting climate impacts on biodiversity.

"We found that different species use different evolutionary strategies to adapt to heat: some species, already warm-tolerant, did not improve their performance, but rather expanded their temperature range. Other species, more adapted to the cold, were able to withstand higher temperatures, but this came at the cost of reduced overall fitness.

"This shows that there is no single way to adapt to climate change, and that the evolutionary history of each species influences its response," says Jennifer Molinet, who is first author of the article and postdoc at the Department of Zoology, Stockholm University.

The new study helps us to understand how different organisms might cope with long-term global warming. The researchers highlight the importance of studying not only individual species, but genetic diversity within and between species.

"This type of research can be key to anticipating which microorganisms, such as yeasts, bacteria or even pathogens, have the most potential to adapt to extreme environments, and how they might change the ecosystems of the future. The results of our article also open new questions about the genetic mechanisms that enable these adaptations," says Rike Stelkens, associate professor at the Department of Zoology, Stockholm University.

"If temperatures change in the future, it is still the history in our genes that determines if and how we can adapt."