A group of researchers from China, the United States, and Russia, including specialists from St Petersburg University, has analysed the genomes of 32 individuals of tigers from different parts of the world. With the help of genetic data, they were able to confirm the traditional taxonomy of big cats, and also understand that modern subspecies were divided about 112,000 years ago.
The findings published in the journal Current Biology will help to protect tigers from extinction — there are only about 4,000 of them left.
The new data made it possible to confirm that within the species of Panthera tigris there are six subspecies: South Chinese, Bengali, Amur, Sumatran, Indochinese and Malayan tigers. The latter was identified as an independent subspecies only in 2004 during a study conducted under the guidance of American geneticist Stephen O’Brien. At present, he is the Head of the Theodosius Dobzhansky Center for Genome Bioinformatics of St Petersburg University.
Scientists were able to find out that the common ancestor of modern tigers lived on Earth relatively recently — from 72,200 to 154,800 years ago. It was during this time interval that there was the Toba volcano supereruption on the island of Sumatra in Indonesia (about 72,000 years ago). According to modern palaeontologists, the event caused a decrease in the average temperature on the planet and led to the extinction of many plants and animals. The authors note that a small number of tigers could have survived this cataclysm and formed isolated habitats in several regions.
Despite the fact that, by evolutionary parameters, the common ancestor of tigers lived quite recently, the scientists found out that modern subspecies have already undergone a natural selection. An important role in this process was played by the ADH7 gene, which was found in the Sumatran tiger. It was associated with the size of the animal. This subspecies could have gradually become smaller, because it reduced its energy needs and began to feed on medium-sized prey such as wild pigs and small muntjaks.
The researchers note that the new data will help to develop successful strategies for the preservation of endangered species.
The authors of the article note that the origin of the South Chinese tiger still remains unknown. The study involved only one individual of this subspecies. Unfortunately, today these animals are no longer found in the wild. Nevertheless, the scientists are planning to continue working with genetic samples of tigers, including the extinct subspecies (Caspian, Balinese, and Javanese tigers), which vanished from the earth during the last century. This work will help to fill the gaps in the evolutionary history of the largest cats on Earth.
The research, conducted by experts from Peking University, the National Institute on Alcohol Abuse and Alcoholism in the USA, the Far Eastern Branch of the Russian Academy of Sciences, the Society for the Conservation of Nature, Hong Kong Ocean Park, the University of Minnesota, and St Petersburg University, has put an end to the controversy over the number of tiger species.