AsianScientist (Dec. 23, 2014) – An article published in Genome Biology has detailed the genomic ‘signatures’ of extinction events in birds. These new insights could be used to help conservation efforts of the endangered Crested Ibis in China and prevent the extinction of other species.
Birds play important roles in ecological balance. They are found everywhere around the globe, with their species numbering nearly twice that of mammals. Unfortunately, the rate of their extinction appears to have increased in the past millennium. Genomics provides a powerful means for discovering molecular signatures of endangered species, which support scientific insights and strategies to assist conservation efforts for those birds.
The Crested Ibis was once widely spread throughout Eastern Asia, praised by ancient Chinese poets as “the red sunsets”. Their population decline began in the last century to the extent that they were thought to have become extinct in the 1960s and 1970s in different countries.
In 1981, one historic sighting happened in China, when seven individuals (from two breeding couples) were identified by experts in the foothills of the Qinling Mountains. An all-out conservation effort was initiated by the Chinese government. The effort, lasting more than 30 years, has resulted in over 2,000 birds in the total population; among them, 500 birds have been released to the wild and the rest remain in captivity in eight local pools.
In the present study, a team of researchers led by Dr. Cheng Cheng from Xi’an Jiaotong University, and Dr. Jun Yu is from the Beijing Institute of Genomics, Chinese Academy of Sciences, compared the Ibis’ genomes with eight other endangered and 32 ‘Least Concern’ bird species.
Their results suggest a few causes of bird extinction. One of them is dichlorodiphenyltrichloroethane (DDT), which was first synthesized in 1874 and widely used as an agricultural insecticide at the beginning of the last century, coinciding with the time when many bird species became endangered. The researchers found that a series of genes related to detoxification became pseudo-genes that lost their function in most endangered birds studied in this series, including the Crested Ibis, the Bold Eagle and the Kea.
Other causes include deleterious mutations in brain function genes and metabolism related genes, and genes which are critical for immunity, which have lower genetic diversity in the Crested Ibis due to the ‘bottleneck effect’.
A common sequence signature of endangered birds is low genome ‘heterozygosity’ in general, which means the severe loss of genetic diversity which reduces the birds’ adaptation to variable environments.
The genetic drift for fixation of changes in brain and metabolism genes of the rescued Crested Ibis population in China is intriguing, and could mean either deleterious mutations in these genes or the possibility of enhanced functions for certain brain behaviors and enhanced metabolism of toxins for survival of the species.
In addition, to trace all the Ibises, the team developed a set of genome-wide genetic markers for DNA profiling and marker-assisted breeding. As more and more species have been sequenced, the researchers hope that the genome data they have published will be useful for the rescue of more endangered species.
The article can be found at: Li et al. (2014) Genomic Signatures of Near-Extinction and Rebirth of the Crested Ibis and Other Endangered Bird Species.
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Source: Chinese Academy of Sciences; Photo: Ron Knight/Flickr/CC.
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