Uncovering The History Of The Tiger Genome

Historic dips in the population from a wildly endangered past have led to a split between genetically diverse tiger subspecies and several inbred individuals.

AsianScientist (Sep. 9, 2021) – While tigers remain genetically diverse overall, some individual tigers are the result of inbreeding—likely due to bottlenecks where population dropped at certain points in history. These findings have been published in Molecular Biology and Evolution.

Like a biological history book, an individual’s genome reflects the unique events that have impacted the species over time. However, even within a species, each individual’s genome can vary very slightly—usually showing up as the difference between physical traits like eye and hair color. Generally, the more genetic variation a species has, the better its chances of survival are.

Fortunately, thanks to recent advances in sequencing technologies, we can now read such biological history books and interpret genetic variations across the genome. With this technology, an international team of researchers from India’s National Centre for Biological Sciences (NCBS), Stanford University and zoological organizations across the world completed a three-year project dedicated to understanding the processes that have shaped genomic variation in tigers.

Despite the significant conservation attention tigers receive, not much is known about their evolutionary history and genomic variation—information that would greatly benefit conservation efforts.

To this end, the team sequenced whole genomes from 65 individual tigers across four subspecies. They used the data to conduct a variety of population genomic analyses to find out more about genetic variability, the impacts of inbreeding, possible events that caused variation, demographic history and local adaptation.

“The tiger is an excellent example of the myriad historic events that sculpt species’ genomic diversity and points to the importance of understanding this diversity as we attempt to stave off extinction of our most precious species on Earth,” said co-senior author Professor Elizabeth Hadly of Stanford University.

Interestingly, their analysis showed that the total genomic variation in Indian tigers was higher than in other subspecies but several individuals showed low variation, suggesting inbreeding. Such inbreeding is likely a result of dips in the population or breeding within small and fragmented protected areas. Additionally, tigers from northeast India were found to be the most different from other populations in India.

The researchers also discovered that the genomes of distinct tiger subspecies and inbred individuals diverged relatively recently, within the last 20,000 years. The data further suggests strong bottlenecks in all tiger populations—highlighting the importance of population size decline and its negative impact on genetic variation.

“Our study reveals that while the total variation in Indian tiger genomes is high, they have also been dramatically shaped by population bottlenecks,” said Dr. Uma Ramakrishnan of NCBS, co-senior and co-corresponding author. “Population management and conservation action must incorporate information on genetic variation.”

The article can be found at: Armstrong et al. (2021) Recent Evolutionary History of Tigers Highlights Contrasting Roles of Genetic Drift and Selection.


Source: National Center for Biological Sciences; Photo: Ranthambore Tiger Team, NCBS.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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