Genetic Diversity for Mitochondrial and Nuclear DNA between Wild and Domestic Pigs

The genetic loss due to domestication in domestic species compared to their wild ancestors can be expected. However, a new research from the Kunming Institute of Zoology found a lack of  reduction in genetic diversity in the nuclear DNA of East Asian pigs which contrasts with the mitochondrial DNA patterns.

Domestication has been generally seen as a process that starts with a small number of wild individuals, which through succeeding generations of breeding, are integrated into human societies and thereby lose almost all opportunities to mate with their wild relatives.  In this study researchers investigated why nuclear and mitochondrial data may be incongruent and presents a backcross scenario reasonable for this system.

The researchers surveyed domesticated pig and wild boar populations of East Asia for variation at nuclear DNA loci. Genetic diversity at nuclear DNA and mitochondrial DNA were compared and the results showed that nuclear DNA has similar levels of diversity in both wild boars and domestic pigs, whereas mtDNA diversity has been reduced in domestic pigs.This maintenance of genetic diversity in nuclear DNA seems to be not due to selection or changes in recombination rates. 

Domesticated pig and wild boar populations also do not appear to be structured geographically, leaving the researchers to conclude that sex-biased introgression is maintaining the high nuclear genetic diversity in domesticated pig populations.

“In conclusion, our data help us better understand the complex demographic histories of East Asian pigs, and bring a practical benefit for the future work on artificial selection. High nuclear genetic diversity increases statistical power in the search for genes that have been subject to artificial selection during domestication, since there is less need to consider the alternative hypothesis of founder effects as a cause of lower diversity in candidate loci for artificial selection," said the authors.

The study was funded bygrants from the National Basic Research Program of China (973 Program), National program for transgenic research from Ministry of Agriculture of China, National Natural Science Foundation of China, Chinese Academy of Sciences, and Bureau of Science and Technology of Yunnan Province.