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Mild, proactive exposure to environmental stress can help biological communities resist severe disturbances and maintain genetic diversity, a recent study from McGill University has found.

The findings are in the journal Current Biology.

Led by Professor Rowan Barrett and Ph.D. graduate Charles Xu in McGill's Department of Biology, the study enhances our understanding of the combined ecological and evolutionary processes that shape how natural communities respond to environmental changes. The findings could have implications for managing biodiversity in the face of increasing anthropogenic stressors, such as climate change and pollution, the researchers said.

The team conducted their study at the Large Experimental Array of Ponds (LEAP) at McGill's Gault Nature Reserve in Mont-Saint-Hilaire. They exposed the natural microbial communities living in the ponds to mild acidification, followed by a more severe acidification event that mimicked potential environmental stressors in real-world ecosystems.

They found that pre-exposure to stressors had an immunization-like effect: biological communities that had previously been exposed to mild stressors were better able to survive and keep their species diversity when faced with severe stressors, compared to communities that had not previously experienced those stressors.

Species sorting and evolution boost ecosystem resilience

The paper highlights the simultaneous processes of species sorting and evolutionary adaptation in freshwater bacterial communities. Species sorting is an ecological mechanism by which species tend to be more common in the habitats that are appropriate for them. Evolutionary adaptation refers to changes in the genetic traits of species that allow them to better survive or reproduce in their environments.

Through metagenomic analysis, the researchers tracked the evolutionary changes in microbial species within the communities.

The study is one of the first to demonstrate both species sorting and evolutionary adaptation working concurrently within natural communities, underlining the importance of these dual processes in predicting how ecosystems will cope with climate change and other stressors. The more resilient species survived the stress, and over time, they also evolved to become even better at handling it. This combination helped the community stay more stable and diverse, even after a severe stress event.

"This research underscores the need to consider both ecological and evolutionary forces when predicting how natural communities will respond to environmental stress," said Barrett. "By integrating evolutionary responses into our models, we can make more accurate predictions about biodiversity change and improve our conservation efforts."

Next steps include further investigations into the long-term evolutionary trajectories of microbial communities and exploration of how different environmental stressors affect genetic adaptation.