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Genetics reveals origin and evolution of blackbuck, chinkara

Reason for divergence: The expansion of grasslands following blackbuck entry into Indian subcontinent could have facilitated the divergence.

Reason for divergence: The expansion of grasslands following blackbuck entry into Indian subcontinent could have facilitated the divergence.   | Photo Credit: Ananya Jana

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Blackbuck ancestors came into India from the Saharo-Arabian region about two million years ago

A regular favourite with poachers and an animal that notoriously made headlines a few years ago, the blackbuck is once again in the limelight, this time, with its story of origin and evolution.

Researchers from the Indian Institute of Science (IISc), Bengaluru, studied four genera of ‘true antelopes’ — Gazella, Nanger, Eudorcas and Antilope — and found that the blackbuck’s (Antilope cervicapra) ancestors came into India from the Saharo-Arabian region about two million years ago and then evolved to its current form.

“If we compare the divergence dates of the blackbuck to the biogeographical conditions in India, we find that the antelopes were part of the fauna that came in through the northwest gateway into India. The very recent formation of the Thar desert could have a been a barrier to the back-dispersal of a grassland specialist like the blackbucks,” explains Ananya Jana, a Ph.D. student at the Centre for Ecological Sciences, and the first and corresponding author of the work published in Molecular Phylogenetics and Evolution.

Diverged in India

The paper states that the lack of blackbuck fossils outside India leads to the speculation that they diverged from their ancestors only after reaching India, long after the intensification of aridification in the Indian subcontinent. The expansion of grasslands following that period opened up new niches, which could have facilitated the divergence of many taxa.

Blackbucks have been confined to the scrubland regions of India, currently seen in most States, except for the Terai region, northeast and the Western Ghats. In the south, blackbucks can be seen up to the Tirunelveli district in Tamil Nadu.

Call for reclassifying

The team also noted that Antilope was not a sister of Gazella, as was previously believed, but was within the same genera. This would call for reclassifying the genus.

“We should probably reassign Antilope to be a species under Gazella. Members of the Gazella genus have certain morphological characters, which were not seen in Antilope, so they were put under a separate genus. Now, molecular studies have shown that the characteristics are not entirely different but have evolved differently,” explains Prof. Praveen Karanth, the team head and one of the authors of the paper.

Usually, researchers use mitochondrial DNA for genetic analysis. However, this team used nuclear DNA, which has genetic material from both parents. They used 12 different nuclear markers for the study.

“We have seen that there are differences in the mitochondrial-DNA and nuclear-DNA trees. Therefore, there are conflicts between molecular data also. We need to carefully look at and interpret the data. It is time that taxonomical studies combine use both molecular and morphological analysis,” adds Prof. Karanth.

Evolution of chinkara

Another interesting finding was that the chinkara (Gazella bennetti), another ‘true antelope’ of India, evolved much more recently about 7,00,000 years ago, probably after the establishment of the Thar desert. These are also found in the hilly terrains of Iran, and are known as Iranian Gazelle. Being facultative drinkers, they were better adapted to the drier, semi-arid region.

Genetics has now helped researchers tell two stories of origin and evolution. Though the blackbucks and chinkara look like sisters they actually may have very different evolutionary histories.

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Printable version | Jan 26, 2020 8:13:50 PM | https://www.thehindu.com/sci-tech/science/genetics-reveals-origin-and-evolution-of-blackbuck-chinkara/article29477449.ece

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