Genetic diversity or genetic variation denotes for changes in the DNA, which is the carrier of the genetic information, when they accumulate over several generations of any population of living organisms. These changes are referred to as mutations, and they are the reason behind natural selection and evolution.
So, how are all these elements related to each other?
When changes in the environment take place, such as the outburst of a new disease, natural selection will act on specific regions of the DNA, known as genes, if they exist in the population endangered by the new disease. Hence, only individuals in the population possessing these specific genes will be able to defeat the disease and evolve in response to the change in their environment. Yet, if the individuals lack these essential genes, they will not be able to resist the threat and will be prone to extinction.
The evolutionary theory explains that low genetic diversity increases the risk of a decline in the number of a population and can ultimately result in extinction; and a case study on cheetahs and lions demonstrated this subject clearly. In this study, lions that have extensive genetic diversity and cheetahs that are well-known for their low genetic diversity were exposed to a potentially lethal virus. This virus swept though the cheetahs and 50 percent of their population was killed as a direct or indirect result of the virus, while lions did not even develop the symptoms of this viral infection. Thus, the outcomes of this study can show that cheetahs, unlike lions, lack the right immune system genes that play a role in warding off the disease. And this can explain why specific populations no longer exist nowadays and why in a single population only certain species survived up to this date.
Can Human Activity Affect Genetic Diversity?
This question was answered by a recent study performed at the University of Copenhagen, Denmark, and published in the journal “Science” on September, 2016. Researchers checked more than 90,000 DNA sequences from 4,500 species of amphibians and mammals, and then coupled each geographic area with the level of genetic diversity of the species it harbors. Finally, they came up with a “Genetic Diversity Map”, which is the first map that links the genetic diversity of animals with their geographic locations.
The “Genetic Diversity Map” revealed that the weather and temperature affect genetic diversity since the levels of genetic variation were 27 percent higher in tropical regions than in colder ones. So, the findings showed that tropical areas are the richest in terms of biodiversity, which further supports the idea that high temperatures result in higher mutation rates. Adding to this, the study illustrated how genetic diversity varies according to human activity, and the diversity was the lowest for amphibians residing in areas with high human activity. In contrast, mammals’ genetic diversity was the highest in areas with intermediate human activity. However, Dr. Andreia Miraldo who is a researcher at the University of Copenhagen and first author of the study commented by saying that scientists do not know if the low genetic diversity puts these populations and species at a risk of extinction, but higher genetic diversity will absolutely make them more resilient to alterations in the environments they inhabit. Dr. Miraldo also said that although scientists do not know if genetic diversity in these regions was low before human activity, this study must serve as a baseline for future studies so that the impact of human activity on genetic diversity can be confirmed.
Conclusion
There is no doubt in the naming of this era, the “Age of Man”, since humans are still damaging the environment extensively on a daily basis. Deforestation, industrialization, land conversion and overhunting, in addition to the enormous disposal of industrial and household wastes, are all few examples of human activities that contribute to harmful changes in our environment. Yet, we do not know for how long our environment will be able to withstand the transformations that humans are making, and for how long humans can endure the consequences of the environmental destruction.
