The role of epigenetics in rapid environmental adaptation: How do threespine stickleback fish in Californian bar-built estuaries rapidly adapt to seasonal salinity changes?

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Many animal species are threatened with extinction from the effects of global warming unless they can adapt. Evolution explains how species emerge and adapt through changes in their DNA. This process takes place over many generations, which may be too slow in the face of climate change. However, many species show remarkable ability to adapt to environmental challenges, indicating that there are more rapid mechanisms. Understanding these rapid adaptation responses may allow us to predict and mitigate effects of climate change and develop conservation strategies. We are studying adaptation in threespine stickleback fish populations in Californian bar-built estuaries. Unlike most stickleback populations that reside in either marine or fresh water, these fish survive seasonal fluctuations from fresh to saltwater. We hypothesize that adaptation to seasonal fluctuations relies on epigenetic regulation. Epigenetic regulation does not depend on inheritance of DNA mutations (i.e. evolution), but instead controls how the existing DNA (genome) is used. Genes form the basic units of the genome, that each contain information needed to make one protein. These proteins are the structural and functional components of cells and tissues. This includes proteins that are molecular sensors and machines that detect and respond to environmental conditions (such as how much salt is in the water). One way organisms may adapt to changes in their environment is if they can store information collected by sensors, and use it to adjust the molecular machines (such as pumps that remove excess salt from cells) that respond to it-essentially preparing for the future. This could occur through epigenetic regulation that controls the output of specific genes. At the molecular level, epigenetic regulation changes how the genome is organized, marking genes for increased or decreased output. Our project will analyse the genome in gill cells to test whether epigenetic regulation can explain how these fish adapt to their fluctuating environment. Fish are essential to the aquatic ecosystem, and to the human population as a food source. Our work may help to understand how fish can adapt to environmental change.