In recent years there have been many studies and breakthroughs in genetic research. A few of these are specific to the White Tiger, while some are about the tiger in general, but have implications for white tigers too.
- Tigers in the wild have fragmented and low overall genetic diversity (which is dangerous for species survival), so every bit of genetic variation – in captivity or the wild – is valuable to preserve.
- Captive tigers, and white tigers specifically, have been found to hold genetic variation no longer found in the wild, and therefore are valuable.
- Cross-bred tigers are also a valuable source of genetic diversity and it may even be necessary for the tiger’s survival to cross-breed subspecies.
- The gene that produces the white coat has been identified, and found to affect pigmentation only – it does not cause defects.
- White tigers are not all inbred
Following are 6 of the important recent studies ordered by year of publication. (Links to the original study or article are in green).
 2008: Captive Tigers Hold Valuable Genetic Diversity
Luo, Shu-Jin et al. Current Biology , Volume 18 , Issue 8 , 592 – 596
Scientists developed a method for testing the subspecies genetic ancestry of tigers and found that 49 of their test group of 105 captive tigers were a “pure bred” subspecies. This included 7 out of 50 tigers that were previously of unknown origin. This means that there could be a large number of “extra” pure-bred tigers available for subspecies breeding programs (14-23%). They also found that:
“The tested captive tigers retain appreciable genomic diversity unobserved in their wild counterparts”
“A wide-ranging identification of captive VSA tigers to assess their potential for inclusion into comprehensive, integrated in situ and ex situ management plans could significantly increase population sizes and help maintain genetic variability and population viability of this iconoclastic species.”
 2009: White Tigers Hold Genetic Diversity no longer in the wild
Sharma et al; Conserv Genet (2009) 10:909–914
Scientists analyzed mitochondrial DNA (maternally inherited) from 13 Indian wild populations of the Bengal tiger, plus captive zoo tigers.
They identified haplotypes (DNA variants) that occurred either throughout all populations, or only in some. One of these haplotypes was found only in captive white tigers. (Note that this is not referring to the white gene itself, which was identified later, but to other DNA variations in this lineage). They also noted that the Bengal tiger has low diversity overall.
“10 Indian tiger haplotypes are now known, which differ from one another by only a few mutations. This low diversity is typical also for other tiger subspecies”
 2013: Wild Tigers Have Lost 93% of their Historic Genetic Diversity
Article: Indian Tigers’ Genetic Diversity: Population Faces Extinction For Lack Of DNA Variety, Study Says “93 percent of the tiger DNA variants from that historical period are no longer present in the current tiger population.”
Sara Gates, The Huffington Post, 05/15/2013
The Study: Demographic Loss, Genetic Structure and the Conservation Implications for Indian Tigers
Samrat Mondol, Michael W. Bruford, Uma Ramakrishnan. Proc. R. Soc. B 2013 280 Published 15 May 2013
Scientists were concerned that an increase in numbers for the tiger population in India was not a good enough indication of subspecies recovery, because:
They sampled DNA from museum specimens of tigers, from the period of about 1850-1950. They compared this with DNA from modern wild tiger populations. They found that:
They also found increased population structure in the Indian tiger (ie differentiation between isolated populations):
 2013: Crossbreeding Subspecies May be Necessary to Save the Tiger
Rachael A. Bay, Uma Ramakrishnan and Elizabeth A. Hadly; Jnl of Heredity, Dec 2013
The Global Tiger Recovery Program aims to double the number of wild tigers by 2022. However, genetic diversity is also extremely important to tiger conservation, so scientists used a predictive genetic model to predict the population growth needed to maintain current genetic diversity of the tiger over the next 150 years. They found that it would need to grow to 60,000 to 98-000 ! Such a large growth is unrealistic, so they recommended that gene-flow between subspecies, and even using captive tigers, would be necessary to ensure the survival of the tiger as a species.
Article: Increase Genetic Diversity to Save Tigers [The Times of India}
“The results showed that for tiger populations to maintain their current genetic diversity 150 years from now, the tiger population would have to expand to about 98,000 individuals if gene flow across species were delayed 25 years. By comparison, the population would need to grow to about 60,000 if gene flow were achieved immediately. Neither of these numbers is realistic, considering the limited size of protected tiger habitat and availability of prey, among other factors, according to the researchers.”
Rob Jordan, Stanford Report, April 15 2014
 2013: The White Gene is Identified
Luo et al, Current Biology June 2013
Scientists identify the gene responsible for the white coat/blue eyes: a change in a single amino acid (A477V) in one pigment-related gene, SLC45A2, that blocks the production of red/yellow pheomelanin while still allowing the black/brown melanin to be produced. This is not at the albino locus, as previously thought, but is the same gene that causes color variation in humans, horses, and chickens. The scientists concluded that it affected only pigmentation, and is a naturally occurring variant.
Article: White Bengal Tiger enigma solved (R. Prasad, The Hindu, May 24 2013)
Related Article: Save the White Tigers By Shu-Jin Luo and Xiao Xu; Scientific American, October 16, 2014
 2013: White Tigers are not all Inbred
The Study: Genetic Diversity of White Tigers and Genetic Factors Related to Coat Color” May 2013, SE Carney
This study measured the amount of heterozygosity (ie genetic variation) in white tigers and orange tigers, and found that both groups had about the same degree of variation.