(Image: Melanie Heckwolf / GEOMAR)
Climate change is rapidly changing ecosystems – this means that animals have to adapt quickly. Researchers have now used sticklebacks to investigate the extent to which it can convey so-called epigenetics. Her conclusion is that this “fast” form of genetic change can make a positive contribution to development – but “adaptation miracles” cannot bring about it.
If you cannot adapt, you will die – this principle has been part of the game of life for millions of years. But humans are now imposing unfair rules on nature: the climate on our planet is changing at a speed for which there are hardly any parallels in earth’s history. The corresponding rapid changes in their environmental conditions pose great problems for many organisms. But can they perhaps adapt to the new challenges evolutionarily? A team of scientists at the GEOMAR Helmholtz Center for Ocean Research in Kiel is researching whether and how animals and plants can adapt. In her current study, the focus was on the importance of the “second level” of genetics – epigenetics.
Research in recent decades has shown that the characteristics of living things are based not only on the sequence of the DNA building blocks, but also on control mechanisms of the genetic code, some of which are inheritable. These so-called epigenetic factors are based, among other things, on chemical switch molecules that sit on the DNA and determine how active a hereditary system is. These genetic regulatory elements can arise from certain factors in the course of life and can then be inherited over generations.
Fast adaptability through epigenetics?
The epigenetic effects therefore have a slightly different meaning than changes in the DNA base sequences, explains co-author Britta Meyer from GEOMAR. The following applies to changes in the genetic sequence: “Individuals with certain inheritable traits that are stored in the DNA can deal with their environment better or worse. Those individuals that are optimally adapted to their environment survive better and thus produce more offspring. In the long term, their properties stored in the DNA will prevail. This process is called selection, ”explains Meyer. However, this selection process takes a comparatively long time, which is becoming increasingly scarce in the wake of rapid climate change.
However, epigenetic processes can work faster. They activate or deactivate areas of the genome that are responsible for certain properties of an organism. As the researchers explain, there are “stable” epigenetic markers that, through selection, contribute to the adaptation of a species in a similar way to the DNA itself. In addition, there are also so-called “inducible” markers that can change during the life of an individual organism. If this happens in the sex cells of the parents, they can be transferred to offspring. As a result, the offspring can immediately be better adapted to changing environmental conditions. These inducible markers therefore give hope that they can ensure the survival of organisms in times of rapid change.
To what extent this hope is justified in the context of climatic change, the researchers have now explored sticklebacks in the Baltic Sea: As part of their study, they examined epigenetic factors and recorded the extent to which offspring are adapted to changing environmental conditions compared to their parents. The model factor was the salinity: sticklebacks have to cope with different salt, fresh and brackish water conditions in different areas of the Baltic Sea. According to forecasts, the salinity of the Baltic Sea could increase as a result of climate change – with potentially critical consequences.
Limited potential
“In order to find out which genetic and epigenetic methods of adaptation the stickleback has used so far, we looked at three stickleback populations from different regions with different salinity levels,” explains Meyer. Specifically, by comparing the genetic sequences and the epigenetic characteristics of DNA, the researchers virtually looked back to see to what extent these changes have shaped different populations.
It turned out that the stickleback populations actually differ in their genetic and epigenetic patterns – which is linked to different tolerances towards changes in salinity. The genetic and epigenic factors relate to hereditary systems that are linked to the regulation of osmotic pressure. In a further experiment spanning several generations of sticklings, the team was able to show that inducible markers can actually contribute to adaptation. But: The contribution is lower than expected, the scientists emphasize.
This is how they come to the conclusion: The adaptability through epigenetics is also limited. “We have to be careful not to over-interpret this exciting, but poorly understood, field of research as the savior of species in climate change,” says co-author Melanie Heckwolf. “Climate change is and remains one of the greatest challenges for individual species and entire ecosystems. The danger cannot be discussed with the current knowledge in epigenetics, ”says the scientist.
Source: GEOMAR Helmholtz Center for Ocean Research Kiel. Technical article: Science Advances, doi: 10.1126 / sciadv.aaz1138