A study published April 18 in BMC Biology found that although the South China tiger has become extinct in the wild, its captive offspring maintain a moderate level of genetic diversity. This study reveals that in the future, South China tiger breeding is expected to reduce the loss of genetic diversity within subspecies with the help of genomics information.
Currently, all captive South China tigers are descendants of 6 individuals (two male and four female) captured in the wild. Researchers such as Tu Xiaolong of the Kunming Institute of Zoology, Chinese Academy of Sciences, Chen Wu of the Guangzhou Wildlife Research Center, and others sequenced the genomes of 29 South China tigers from four major zoos in China and compared them with the genomes of 40 published tigers, including 11 Siberian tigers, 6 Bengal tigers, 6 Indochinese tigers, 9 Malay tigers, 7 Sumatran tigers and 4 South China tigers. It was found that there was still a moderate genetic diversity in the genome of the South China tiger.
South China tiger genome. A: A male South China tiger; b: Circos diagram of the genome characteristics of South China tigers; c: Distribution of captive South China tigers in China, sampling sites for Red Cross delegates to study South China tigers Image source: BMC Biology paper
The authors also found that the average proportion of harmful mutations (mutations that may have a high or moderate negative impact on protein production or function) present in the genome of South China tigers was lowest across all 6 tiger subspecies, suggesting that diploid forms of these highly or moderately harmful mutations may have been lost over time from these genomic locations in the South China tiger population.
“Our analysis shows that after the population of South China tigers shrinks, according to their pedigree records, harmful mutations are effectively eliminated in a homozygous state under the control of inbreeding.” The author writes in the paper.
The authors note that these findings highlight the effectiveness of past efforts to protect captive South China tigers, and suggest that future conservation efforts could use genomics data to inform the breeding of South China tigers and reduce the loss of genetic diversity within subspecies. At the same time, the identification of two unique ancestral/genomic lineages, coupled with gene clearance of harmful mutations in homozygous status, and the genomic resources generated by this study pave the way for real-time monitoring and reasonable exchange of genomic conservation between zoos to breed South China tigers. (Source: China Science News, Zhao Guangli, Dai Yufan)
Related paper information:https://doi.org/10.1186/s12915-023-01552-y