Evolution is the result of environmental pressures forcing species to adapt, and few environments exert pressures like the Chernobyl exclusion zone. A new study has revealed evolution in action as frogs within the radioactive region seem to be turning blacker than those outside the zone.
The explosion at the Chernobyl Nuclear Power Plant in 1986 released a huge amount of radioactive material into the environment and it is now at the center of an exclusion zone encompassing 1,000 sq miles (2,600 sq km). If there’s a silver lining to be found from one of the worst catastrophes humans have ever unleashed on the world, it’s that the area has become a nature reserve that houses a range of species.
This unique environment offers scientists an unprecedented glimpse into a microcosm of nature – in this case, evolution. How might animals within the exclusion zone be adapting to the higher levels of radiation in their environment?
In 2016, the team on the new study found a few Eastern tree frogs in the Chernobyl exclusion zone that were black, rather than their usual bright green color. The researchers wondered if this was the result of natural selection from the higher radiation in the area.
To investigate, the team returned for follow-up studies over the next few years, collecting more than 200 eastern tree frogs from 12 ponds with different levels of radioactive contamination, including four sites outside the zone for comparison’s sake.
And sure enough, they found that the closer the frogs lived to areas with high radiation levels, the darker they were. Those individuals living within the exclusion zone were on average 43.6% darker than those outside, with some of them almost pitch black.
Why would this environment turn frogs black? The team says that melanin, the pigment that darkens the skin of animals, works to reduce cell damage caused by radiation. Normally that’s ultraviolet radiation from the Sun, but it’s also been shown to protect against ionizing radiation like that present at Chernobyl. This means that individuals with darker skin will be less likely to experience cell damage after radiation exposure.
The team hypothesizes that at the time of the accident, frogs in the area that happened to be darker suddenly had an advantage in the new extremes of this environment, meaning they were more likely to survive and reproduce. After three and a half decades and more than 10 generations of frogs, dark skin is now the norm in the exclusion zone.
It’s a fascinating little case study into evolution, and further work could help scientists better understand the impacts of nuclear disasters and how ecosystems can recover.
The research was published in the journal Evolutionary Applications.
Source: The Conversation
The researchers sort of forgot about them, until they checked 17 years later. Over that time, the birds developed very significant changes, that were consistent with the new environment. It looks like these birds are pre-programmed with the ability to change features in response to pressure from the environment, via. regulatory genes, that used to be called junk DNA.
These frogs may not have developed any new genetic ability, but like the finches, they had the pre-programmed ability to be darker when needed.
On the other hand evolution does not take millions of years. It could happen in one generation but normally goes slowly UNLESS there is a big environmental shift such as in this case.
Next point, evolution of one species to another is based on whether the two kinds can mate and have kids that can mate. If not then they are two species. It is STILL evolution even if the animals are not changing into a new species!
Evolution only requires a .3% improvement in reproduction to dominate. The rate of death or reproductive failure for frogs around Chernobyl was probably much higher than that, which increases the rate of evolution. I'm sure there have been experiments with 100% selection (killing off any spawn with or without a specific trait). How many generations does it take to change, for example, a Dalmation to be either pure white or pure black if you applied 100% selection?
Those frogs would also have a higher mutation rate due to the environment, which would increase the rate of evolution.
The interesting thing about epigenetics, is that it allows a parent to pass a trait they acquired in life, to their dependents. Though, another possible mechanism, is that the epigenetic part of the DNA are designed to vary a bit from generation to generation. So, the finches, or the frogs, each vary a bit from their parents. So if there is an environmental stress or change, each generation is able to shift a bit further away from the first generation. Natural selection being the driving force. But, the pre-programmed ability to shift colors or beak sizes, has to be there first.
In Russia, they were trying to breed Foxes to be more docile for the fur trade. They kept selecting out for breeding the Foxes in a litter that were more accepting of Humans. After 44 generations of picking out the least aggressive Fox kits, a sudden set of changes appeared. The ears were long and floppy, and the coat changed from reddish color to brown and spotted!! Those Fox kits were very friendly, and could even be petted, just like a Beagle or other puppy would be! But as far as I know, no one thought to try breeding a modern day wild Fox with the docile ones, to see how far back down the evolutionary line the aggressive behavior of the new kits would return, if at all. Would it go back all the way, or to somewhere in the middle, or just as tame as the floppy eared ones?? We may never know, because that kind of research takes lots of time and money.