Climate change scenarios paint a challenging picture for the health and persistence of fish populations. This is particularly true for cold-water fishes, where an increase of 3° C in water temperature is predicted to cause a 20% decrease in the abundance and distribution of cold-water salmonid populations. Cold-water fishes found in freshwater lakes, such as brook trout (Salvelinus fontinalis), are likely to be particularly hard hit, as they cannot easily escape increasing temperatures due to a lack of options for dispersing. Despite the almost certain negative effects of climate change on cold-water species and ecosystems, we have a poor understanding of how local adaptation will interact with future environmental conditions to reorganize species’ distributions and abundances. Understanding the genetic mechanisms leading to thermal tolerance, and differences in these mechanisms among populations, is vital to predicting how populations might respond to climate change. In this study, we experimentally identified the genes and molecular pathways associated with response to thermal stress in brook trout, as evidenced by gene expression.
We used a common garden and RNA-sequencing experiment to identify genes that are differentially expressed in response to thermal stress. We found populations from habitats with a history of extreme heat events had different molecular responses to heat stress than populations from habitats containing thermal refuge from heat events. We also found differences in the acute and acclimation responses to heat stress across habitat types. Understanding population and individual differences in the capacity to tolerate changes in climate, and the molecular mechanisms that control these differences, will aid in making predictions about which populations are most vulnerable or resistant to the negative effects of climate change.