ON THE EDGE OF EXTINCTION - A - THE TIGER (Panthera tigris)

[Rishi]

(08-20-2018, 09:32 PM)peter Wrote: 'A REVISED TAXONOMY OF THE FELIDAE' (CAT-news, winter 2017, pp. 66-67)

The revised taxonomy of the felidae (see title) is based on two studies. One of these is 'Planning tiger recovery: Understanding intraspecific variation for effective conservation' (Wilting et al., 2015).

Although the article resulted in discussions, most authorities more or less agree with the recommendation to distinguish between two tiger subspecies only: mainland tigers (Panthera tigris tigris) and Indonesian tigers (Panthera tigris sondaica). The main reason is it facilitates conservation. Here's the link to the article:

http://advances.sciencemag.org/content/1/5/e1400175

As to the discussion on Indian and Amur tigers on this thread.

In the article mentioned above ('Planning tiger recovery: Understanding intraspecific variation for effective conservation'), regarding mainland tigers, a distinction is made between a northern (virgata and altaica) and a southern (amoyensis, corbetti and tigris) 'management unit'. 

Sondaica, therefore, is right in that most authorities today distinguish between two tiger subspecies only, but he omitted info on the northern and southern clades (regarding mainland tigers). 
 
Here's the link to 'A revised taxonomy of the felidae':

https://repository.si.edu/bitstream/handle/10088/32616/A_revised_Felidae_Taxonomy_CatNews.pdf?sequence=1&isAllowed=y

The special edition of CAT-news features in post 1,279. Comments in posts 1,285 - 1,286 - 1,289 - 1,291.

Although most agree with the proposal on two tiger subspecies only, the discussion on tiger subspecies hasn't been concluded.  

As to captive tigers. All zoos and facilities distinguish between Sumatran tigers, tigers from southeast Asia and Amur tigers.

Thanks for that.

The subspecies is actually a kinda vague term. For example, tigers of northeast India were much better linked indo-china than central India. Two adjoining  "subspecies" literally merge into each other with no definite dividing line...

*This image is copyright of its original author

Even among classic Bengal tigers, the tigers residing far south of peninsula can be visibly differentiated from the tigers of Shivalik (Himalayan foothills). The same could probably be said for Indochinese & Malayans.

Other than being grouped in conservation units, the recent extensive genome mapping has shown many local variations amongst India's tigers. Some info are gathered here in the In What Groups Can We Divide Bengal Tigers thread. 

ResearchGate link to original study: High coverage genome sequencing and identification of genomic variants in Bengal tigers.

Quote:Bengal Tiger genome sequenced
This genome was compared with that of a Amur or Siberian tiger, the new data reveals major variations between the two.

---

20 May 2018, India

The genome of the Royal Bengal tiger, an endangered big cat, has been mapped to generate a high-quality draft genome sequence of the animal.

The scientists from the Centre for Cellular and Molecular Biology (CSIR-CCMB) and a Hyderabad-based private company carried out the sequencing and identification of genome variants in Bengal tiger.

During the study, it was observed that "For a very long time it was believed that single nucleotide variants (SNVs) contribute to a majority of the individual genomic variations. Now it is recognized, albeit poorly understood, that much larger changes in the genome like structural variants and copy number variants also contribute significantly to disease susceptibility, phenotypic variations and immunity."

This genome was compared with that of an Amur or Siberian tiger, the new data reveals major variations between the two. Amur tiger occurs in sub-temperate and snow-covered habitats while the Bengal tiger occupies diverse tropical habitats like Himalayan foothills or the Western Ghats.

Insights can be obtained through the Genome data. The genetic differences at the individual level which ranges from a single nucleotide to large structural variants can also be known through it. It provides information about the role of gene variants in adaptation to the environment and disease susceptibility.

Dr Rakesh Mishra, Director CCMB said that genome sequencing will help in the precise understanding of the evolutionary linkage of the organism. He also added that epigenetic analysis will be possible once the genome is available.

Dr. P. Anuradha Reddy, the lead author of the paper said that the numerous SSRs and SNVs identified in the genome can be used to strengthen forensic evidence in tiger poaching cases.

Now, i understand that the ScienceMag link you'd provided clearly says "...differences may have been overemphasized simply owing to fragmentary sampling along a more or less complex cline of variation (4, 13). This was recently illustrated for Bengal tigers, where seemingly clear molecular differences among current Bengal tiger populations (14) vanished after museum specimens from extinct Bengal tiger populations were included in analyses"...suggesting that historical tiger populations might have been much less dissimilar.

However most Indian habitats are still surprisingly well-connected even today & with recent increase in number, tigers have been popping up everywhere.

*This image is copyright of its original author

Indeed mutual isolation of populations due to poaching in unprotected corridors could be partially responsible, but increase in numbers & better management at landscape level are the solution.
The regional genetic uniqueness & adaptions would still have to be protected individually. Whatever intermixing takes place must happen naturally... unless they're a lost cause like Caspian or Chinese tigers.

Bottom line, even if all of Mainland Asia's tigers were indeed one subspecies, it won't make any change from conservation standpoint. 
Older scientific studies get proven wrong all the time, & this is genetics were taking about. IMO it would be an extreme folly to risk polluting the tiger populations.

Indian zoos have already interbred tigers from different parts of India & severely botched up future rewilding prospects. Reply