Some Indian tigers are inbred: Study

A new study has found that while Indian tigers have a high amount of genetic variation, some individuals are inbred. Scientists said the findings reveal population bottlenecks and ongoing impacts of habitat fragmentation.

The findings mean that the country can no longer just count on the success of tiger populations by numbers alone.

"Our study reveals that while the total variation in Indian tiger genomes is high, they have also been dramatically shaped by population bottlenecks. The genomic variation of Indian tigers continues to be shaped by the ongoing loss of habitat connectivity,” said Dr Uma Ramakrishnan, a molecular ecologist at the National Centre for Biological Sciences (NCBS), who is the co-senior and co-corresponding author of the study.

She added, “Population management and conservation action must incorporate information on genetic variation. Doing so will help India maintain the gains in tiger conservation achieved so far.”

Novel data at the Stanford University found that Russian far eastern tigers have one of the lowest genetic diversity of tiger populations worldwide, that they have no trace of inbreeding.

“Why do the Russian tigers have the least amount of variation and the least inbreeding? We think it is because they have large, connected habitats, which allows them to mix freely,” Dr Ramakrishnan said.

She added that the inbreeding in India could have transpired over a period of just the last 100 years. What will happen in the next 100 years? “Further studies need to be carried out. But we need to facilitate connectivity between tiger populations,” she said, adding that the finding was, however, not yet a cause for alarm.

“The genetic mixing is an ongoing process and we have not yet seen ‘inbreeding depression’ which would be manifested by tigers with bad mutations,” she said.

The team sequenced whole genomes from 65 individual tigers from four subspecies, with a specific aim to enhance genomes from wild tigers in different habitats in India. They used these data to conduct a variety of population genomic analyses.

Co-senior author Elizabeth Hadly of the Stanford University described the tiger as a good example of the historic events which sculpt a species' genomic diversity. “It points to the importance of understanding this diversity as we attempt to stave off extinction of our most precious species on earth. While some populations demonstrate the importance of adaptation to local conditions, other evidence suggests that particular populations may suffer the effects of climatic change in the Anthropocene.”

The researchers added that such information will be critical to the success of genetic rescue efforts, which should take local adaptation into consideration.

In addition to NCBS and Stanford University, researchers from zoological parks and NGOs across the world were involved in the three-year project. The study was published in Molecular Biology and Evolution.