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06-05-2015, 08:58 AM( This post was last modified: 06-05-2015, 09:08 AM by GuateGojira )
To be or not to be, that is the problem...
Based in genetic and biogeographical studies, tiger subspecies are just an artificial creation, based in human interference, according with Dr Kitchener, however Dr Luo and her team presented evidence that there is enough genetic differentiation to separate "subspecies". However there are questions that the genetic studies has not answered in its own results, like why the Bengal tigers are completely separated from the other subspecies and closer to Sumatran ones in the diagrams? Or why there is genetic "differences" between Malayan and Indochinese tigers but there is no one based in Morphology? This last is incredible, as morphology was the base for the establishment of all the traditional 8 putative subspecies.
In fact, if we see how many tiger specimens has been studied by old taxonomist, there are not even 20 animals used, at exception with the over 27 Indochinese specimens used by Mazák. The problem with this is that there are not enough specimens to study and just in India, for example, there are enough differences between populations to classified them as different "subspecies", following the old taxonomy. Check that in north India, tigers are as large as the Amur ones, in Southern India they are like the Indochina specimens or larger, and in the Sundarbans they are like the Island tigers. However, ALL those variations are just one single population.
Dr Kitchener stated that all those differences are just clinal, and modern studies on skulls from J. H. Mazák showed that the only difference is between the Mainland-overall, the Sumatran and the Java-Bali tigers, in other words, just three subspecies. Interestingly the Caspian tiger skulls are like the "generic" mainland tiger with characteristics of all the populations, showing a previous separation before the sub-specification of all the other populations.
From all what I have read and study, South China-North Indochina population is the original one (those that survived the Toba eruption, a very small group), cranial and strip patterns are just variations and irrelevant in the taxonomy right now. Latter, one population spread to Central Asia via the silk corridor and give origin to the Caspian population, which lived and evolved in the areas with plenty of water. However, the population of China spread to Indochina and gives origin to new populations as far as Malaysia and Myanmar, but not as north as Manchuria (not yet) and not into India which was very dry (a lion paradise in that moment). Still, the Sunda shelf was connected to Malaysia up to 20,000 years ago, which suggest that possible, there was some genetic interchange, giving origin to the Sumatran tigers, which get isolated with the rise of the water.
At 12,000 years ago, tigers began to spread to India, which was more wet and the Caspian tigers already colonized the Manchuria and Amur region trough the north of Asia, avoiding the desert of Gobi. The Sumatran population and Java-Bali were separated with they own group.
The true separation of the mainland tigers in south east Asia was until the heavy persecution of the humans, in Russia the separation between the Caspian and the Amur tigers was just about 200 years!!! The separation between Indian and Myanmar tigers was never clear, as the river used to separate them (Irrawaddy - Ayeyarwaddy) can be crossed easily by any tiger. The isthmus of Kra is nothing for a wild tiger, it was until the human pressure that this geographic bottle neck really affected the animals in the area. From my point of view, mainland tigers were always capable of crossing any barriers, except deserts and the tallest mountains. There is no possibility of discrete "subspecies" and even when they could exist (like state Dr. Luo), these can't be fully separated.
From my point of view, there are/were only three subspecies:
Mainland - Panthera tigris tigris.
Sunda - Panthera tigris sondaica.
Sumatran - Panthera tigris sumatrae (other will say tigris x sondaica).
Interesting a new study of Dr Yamaguchi showed that Sumatran tigers are more closely related with the Sunda tigers than the Mainland, suggesting that the interconnection between the three islands lasted much more after the separation from mainland, and the tigers were probably able to travel between that large original island that latter were separated completely in Sumatra, Java and Bali.
However, modern human intervention was successfully separated tiger populations. The Amur tiger is the most differentiated, although is the most modern (separated from the Central Asia population about only 200 years), has the most specialized skull and is fully different than those of other areas like India, Myanmar, South China or Indochina. Those of India are very close to Indochina, while those in South China are more "primitive", but still can be fitted very well with those of Indochina and even Malaysia, morphologically speaking. The genetic study of Dr Luo probably present modern separations of the "core" populations, which are/were probably different between them, but all the "buffer" populations, now extinct, probably hold the key of the real interconnection between the original tiger population.
In the present, the populations of tigers are so fragmented that they should be conserved like the taxonomy proposed by Luo et al. (2004) and Driscoll et al. (2009), after all, modern Zoos already had they Studbooks organized in that way:
1. Amur-Caspian tiger - Panthera tigris altaica (virgata should be the correct one, as is older in the taxonomical archives).
2. Bengal tiger - Panthera tigris tigris.
3. Indochina-Malayan tiger - Panthera tigris corbetti (I am not agree with the separation, it seems more like national pride).
4. South China tiger - Panthera tigris amoyensis (the African population is the best at this moment, for this group).
5. Sumatran tiger - Panthera tigris sumatrae.
Now, what about the "re-introduction"? Dr Driscoll proposed the reintroduction of Amur tigers to the Caspian region, however other tiger experts (I forgot they names) greatly criticized this idea, after all, why to reintroduce tigers in new areas when those in they native territories are still poached, killed and in great danger??? I am against any reintroduction, we most stop the bleeding first, there is no need to create new wounds.
