Why in the news?

• Recently, a team of scientists has resolved the genetic mystery of Simlipal’s so-called black tigers.  
• The Simlipal Tiger reserve is situated in Odisha.
• The study found that a single genetic mutation in these tigers caused black stripes to broaden or spread into the tawny background.
• Simlipal’s small and isolated tiger population led to inbreeding and the anomalous phenotype characterised by wide, merged stripes. 
• The loss of genetic diversity is evident from the low heterozygosity — chances of inheriting different forms of a particular gene from each parent — in Simlipal (28%) compared to Central India (36%). 

Characteristics of Tiger:

• Tigers have a distinctive dark stripe pattern on a light background of white or golden. 
• A rare pattern variant, distinguished by stripes that are broadened and fused together, is also observed in both wild and captive populations. This is known as pseudo-melanism, which is different from true melanism, a condition characterised by unusually high deposition of melanin, a dark pigment.

Consequences:

• Inbreeding of such tiger populations will be subject to genetic drift (chance events), and inbreeding depression (decreased survival). 
• Overall, such tiger populations have a high chance of extinction.