The current rate of climate change exceeds historical events by 1-2 orders of magnitude, which will make it difficult for organisms and ecosystems to adapt. For a long time it was assumed that adaptation was only possible through changes in the genetic makeup – the base sequence of DNA. Recently, another level of DNA information, namely epigenetics, has appeared.
Using a fish species from the Baltic Sea, the threespine stickleback, an international team investigated whether and how epigenetics contribute to adaptation. “Our experience shows that epigenetic modifications affect adaptation, but also that changes from generation to generation are smaller than previously assumed,” says biologist Dr Melanie Heckwolf from the GEOMAR Helmholtz Center for Ocean. ResearchKiel. She is one of the authors of the study, which has just been published in Scientists progress.
But what distinguishes changes in DNA from changes in epigenetics? “Individuals with certain inherited traits encoded in DNA can cope with the prevailing environment better than others. On average, these individuals can cope better with their environment, thus surviving longer and producing more offspring. In the long term, their characteristics encoded in the DNA will prevail. This process refers to natural selection,” explains GEOMAR’s Dr. Britta Meyer. However, selection takes time, and time is running out in the face of rapid climate change. .
In contrast, epigenetic processes chemically influence DNA structure. They turn on or off areas of the genome that are responsible for certain traits or responses to environmental conditions. On the one hand, “stable” epigenetic markers, by natural selection, contribute to adaptation in the same way as DNA itself. On the other hand, “inducible” markers are those that can change over the lifetime of an individual. In theory, if this occurs in the parent’s gametes, their offspring have an advantage in coping with their environment. Many scientists therefore expect inducible markers to react particularly quickly and thus ensure the survival of organisms in the face of rapid changes.
The research groups of Prof. Dr. Thorsten Reusch (GEOMAR, Germany) and Dr. Christophe Eizaguirre (Queen Mary University of London, UK) investigated whether and how these stable and inducible markers contribute to adaptation. They use the Baltic Threespine Stickleback because it is currently adapted to different salinity conditions ranging from salt water to fresh water. Moreover, the Baltic Sea is a natural laboratory for climate change research as the effects of climate change are already evident there.
“In order to understand how fish react to the consequences of climate change, we collected stickleback populations from different regions of the North Sea and the Baltic Sea with different levels of salinity,” explains Dr Meyer. The team found that the different populations differed in their genetic and epigenetic makeups and also had different tolerances to changes in salinity. In an experiment involving two generations of sticklebacks, the team was also able to show that inducible markers enhance the second generation’s response to environmental changes, although to a lesser extent than originally assumed.
Overall, the study shows that organisms will eventually reach their limits in responding to climate change, even with epigenetic adaptive modes. “We must be careful not to overinterpret this exciting but poorly understood area of research in epigenetics as a magic bullet against climate change for all species,” says Melanie Heckwolf. “Climate change is one of the greatest challenges to species and ecosystems, and the natural mechanisms species have to respond may not be sufficient if climate change remains so strong and rapid.”
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Material provided by Helmholtz Center for Ocean Research Kiel (GEOMAR). Note: Content may be edited for style and length.