July 2, 2009

Amur Tigers Face Genetic Hurdles To Revive Population

Researchers from Canada, Japan and the US have completed an extensive genetic survey of the rare Amur tiger to show the species' chances of survival in the future.

Led by Michael Russello and Philippe Henry of the University of British Columbia, in Kelowna, Canada, the team took nuclear DNA from 95 Amur, or Siberian, tigers in the wild. The sample size translates to up to 20 percent of the tiger's remaining population of about 500.

"Although the census population size of Amur tigers is closer to 500 individuals, the population is behaving as if it were the size of 27 to 35 individuals," Russello told BBC News.

What they found was the lowest recorded genetic diversity of any tiger species.

"However, what is remarkable about the Amur tiger is how much lower the effective population size is than the census size," Russello added.

Researchers also noted that the Siberian population is split into two populations that do not come together regularly. They are separated by development between Vladivostok and Ussurisk.

"There is little sharing of genes across the development corridor, suggesting that these two populations are fairly discrete," Russello said.

"In actuality, it seems that Amur tigers are residing in two, fairly independent populations on either side of the development corridor between Vladivostok and Ussurisk, further lowering the effective size for each from 26 to 28 for Sikhote-Alin and 2.8 to 11 for Southwest Primorye."

Researchers say the effort to open the corridor needs to be stronger in order to save the Southwest Primorye population.

However, Russello's team noted: "there are gene variants found in captivity that no longer persist in the wild."

"Now that it is known which individuals possess which gene variants, managers will be able to selectively breed to help preserve the unique and rare gene variants," he told BBC News.

"The implication is that this variation may be used to re-infuse the wild population sometime in the future if reintroduction strategies are deemed warranted."

The Amur tiger population was nearly wiped out completely during the 20th century. But a ban on hunting has been in place since the 1940s that has helped the population to bounce back to an estimated 500 in the wild and 421 in captivity.


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