WildFact
›
Premier Section
›
Edge of Extinction
ON THE EDGE OF EXTINCTION - A - THE TIGER (Panthera tigris)
ON THE EDGE OF EXTINCTION - A - THE TIGER (Panthera tigris)
|
ON THE EDGE OF EXTINCTION - A - THE TIGER (Panthera tigris)
|
The issue with the Wahnsien form being the direct ancestor to our modern species is the mandible which is we concluded to be very recent. 200 kya isn't enough time for such drastic changes, especially considering when the skull morphology of the Ngandong form is closer to the modern forms. Just considering the Manchurian mandible and the Ngandong mandible, they're different.
Another aspect to note is that the Wahnsien form has robust metapodials not seen in modern tigers and all Sunda forms. If we conclude that the Manchurian mandible is of the same species that Hooijer identified as P.t. acutidens (and our date estimate is correct), 200 kya again isn't enough time for such drastic metapodial thinning. Remember Xue et al. (2015) found genetic evidence to support my theory that there was a large pandemic Ngandong tiger population in Sunda and maybe even southern China. I'm more inclined to say that the rising sea levels separated the population, leaving the island forms and mainland forms to evolve. The Wahnsien cat likely went extinct by the Holocene by this logic. 
Could the older form of tigris coexist with the recent form for a while until the end of the Pleistocene?
There is a chance that Wanhsien tiger turn out to be interspecific with both Mainland tiger and Sunda tiger? 
Tigerluver, the problem here is that your analysis of the Wanhsien tiger is based in a single large mandible, and we most face the fact that we don't know its origin or if is actually a tiger. Deformation for fossilization is also a good explanation, like the skull A.M.N.H. 18624.
About the time, 200,000 years is enough time for such a change and even more, look that less than 100 years were needed to change from an average Central Indian tiger to a dwarf Sundarbans population, and about 50 years and a great extermination caused a greatly reduced body mass in the modern Amur tigers. Imagine a small population of survival tigers after the great destruction of the Toba eruption, trying to survive with the few animals still alive, they probably changed its morphology (talking of robustness and metapodials) in order to adapt to this new habitat. So yes, 200,000 is enough time from my point of view, check that with less than 70,000 years the Amur and Javanese tigers are completely different, even when the overall population was still interconnected at about 20,000 years ago, according with Kitchener and Dugmore (2000). About the Ngandong tiger, it is possible that there could be a large population, but check the fact that the skull have more characteristics from the Sunda and not from mainland, suggesting that this population was from the island, not from the continent itself. I will like to see the document of Xie et al. (2015), could you put it here please?
I agree with issues completely Guate, therefore I kept pointing out under that my theory is under those assumptions. I don't really have any argument against your points. Rather, I'd like to build off them.
Why would robustness of the metapodials change post Toba-catastrophe when the Sunda forms already underwent such a change in your opinion? Having a pandemic tiger population would not prevent ecotype formation, as tigers getting from China to Java at significant rates is unlikely, causing the differences you have pointed out. Distance can be enough of a allopatric speciation factor. P. atrox and P. fossilis were pandemic technically, but the distance diverged the lineages a bit. Correct, I also feel that the Javan tiger's oddly large feet and larger dentition are a remnant of its ancestor. Ecologically, it's doubtful that such a large carnivore would be restricted to a small range as well, therefore I highly doubt the Ngandong tiger was restricted to Java (which did not exist as we know it today anyhow). Before I try to give my take on the tiger lineage expansion, what order do you guys have? The lack of fossils make everything much more difficult to argue or prove.
I do agree with tigerluver's theory.
During the Pleistocene China, there was a large swamp area in the central part that served as a natural geographical barrier between North China and South China, and the swamp area only disappeared very recently like 1000 BC. And no wonder that Amur tiger managed to colonize Manchuria via Central Asia, not via China, because the path was blocked by the swamp area. The southern form of the Wanhsien group must once have a lot of interactions with the Sunda form since there was a land bridge when the sea level was lower. The southern form of the Wanhsien tiger got heavily altered via the intermixture with the Sunda form, while the northern form of the Wanhsien tiger still remained relatively isolated from their southern cousins and without the admixture from the Sunda form, that's why they look more distinct and primitive. I still think that both Panthera youngi and the Manchurian mandible could likely represent the unaltered northern form of the Wanhsien tiger.
The information of GrizzlyClaws in very interesting, and help to build our panorama of tiger expansion. Could you show references of that swamp habitat in that time?
The intermix of Sunda and Mainland tiger could explain why the robustness of the metapodials was smaller, but I have found another problem: time. As far I know, ther is not any exact or modern methods of the fossils from Wanhsien, and those metapodials could be older than we think, even older than those of Ngandong. If this is true, a cline on size could explain the reduction, followed of course by the great genetic bottleneck after the Toba event, which sustain my previous statement. Also, even if the Sunda forms already have the narrow metapodials, that don't prevent the mainland forms of repeat the same change, just like some mainland tigers do have the narrow occiput of the island forms even in modern times. Your point on the pandemic species is very true, but these differences will be clinal, like Kitchener pointed out and based on they proper ways of life, habitat and prey. So like I said, if in just 70,000 years those allopatric differences were very marked between Amur and Javanese tigers, imagine what would happen in 200,000 years! I think that the Ngandong tiger lived in the entire Sunda shelf like the dominant predator, an area larger than modern India, and probably mixed with the northern Wanhsien tigers without any problem. However, something punch my head, the case of Panthera atrox and Panthera spelaea, which lived also very close in Noth America but never mixed, based in genetic differences. I know that this was probably not the case with the tigers, as they were always very close and never isolated, but I think that we could take in count such an scenario at some point. Still, the idea that the Wanhsien tiger in the south area could be altered by the constant contact with the northern Ngandong population is very probable and at the end, the mixed population could be the only survivors of the Toba event, a group of tigers with large size but with less robust limbs, a mix of both worlds. I think this could be plausible. By the way, thanks for the document Tigerluver, I have lost it in my database. [img]images/smilies/smile.gif[/img]
I think we could learn a bit about the geology of the Yangtze River, the large river that splits China into North and South.
https://en.wikipedia.org/wiki/Yangtze BTW, I learn this geographic knowledge from my father, since he is a Chinese from Taiwan. Back until 1000 BC, there was a large marshland in the Central China known as the Yunmeng lake, and this marshland had mostly disappeared, and these smaller lakes are the remaining of the huge marshland. https://en.wikipedia.org/wiki/Dongting_Lake https://en.wikipedia.org/wiki/Poyang_Lake https://en.wikipedia.org/wiki/Lake_Tai Otherwise, I see no reason why Amur tiger had to bypass this area in order to reach Manchuria.
In my head, clinal changes result in new ecotypes, which to me is my defintion of a subspecies, which is that the populations are genetically different but not reproductively incompatible.
The Wahsnein fossils are around middle Early Pleistocene to early Middle Pleistocene (ShaoKun et al. 2013), so a few hundred thousand years before the Ngandong/Trinil form. Excellent information GrizzlyClaws. So there was another allopatric speciation factor it seems.
Despite that the southern population of the Wanhsien tiger had been heavily mixed with the Sunda tiger, but some of the mixed offsprings could still display some morphology (phenotype) of the original Wanhsien tiger.
That's why some skulls of the South China tiger do match with the unaltered northern form of the Wanhsien tiger. Some South China tiger could display even greater similarities with the Panthera youngi and Manchurian mandible, so this could be a genetic throwback as well.
Check this South China tiger skull together with the skull of the Wanhsien tiger:
 *This image is copyright of its original author See how square is its mandible in comparison with other tigers, for example, the Amur ones, but it looks similar to those of Java. Indian and Amur tigers, been the most modern, present the most elongated mandibles in the symphysis and are very different from the South China form. Sadly, the skulls that I have from Indochina don't have mandibles for comparison.
Yes, both Panthera youngi and the Manchurian mandible got shorter part in the symphysis.
And here is Panthera youngi, although the part in the symphysis is missing, but the square mandibles still look very familiar.  *This image is copyright of its original author  *This image is copyright of its original author  *This image is copyright of its original author  *This image is copyright of its original author
If you subscribe to the model proposed in this new paper, then I still think it would be better to have the three subspecies instead of two. That is north Asian tiger, south Asian tiger and Sunda tiger (obviously covering all the currently recognized subspecies). The idea that the entire Asian mainland all belong to a single subspecies is very difficult to swallow for me, it's a HUGE area and most other carnivores are subspeciated at smaller areas.
Well, the Northern Asian tiger and the Southern Asian tiger are differentiated as two separated clades within a continental subspecies, just like many African lions from different areas just belong to a common subspecies.
I think the main reason is there is no significant geographical barrier to truly genetically isolate them, unlike the one between the Mainland tiger and the Sunda tiger.
Note the proportionately large dentitions that both the South China and Wahnsien form possess. The Ngandong skull is the opposite in this regard. @GuateGojira, which document is that figure from?
(07-05-2015, 09:30 AM)'tigerluver' Wrote: Note the proportionately large dentitions that both the South China and Wahnsien form possess. The Ngandong skull is the opposite in this regard. @GuateGojira, which document is that figure from? Are the dentitions from the Panthera youngi and Manchurian mandible large or small? |
| Users browsing this thread: |
| 9 Guest(s) |