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

[peter]

(12-23-2017, 10:09 PM)GrizzlyClaws Wrote: It is intriguing that the most impressive fossil records of the Amur tiger still belonged to Manchuria, and based on the report, I am assuming that the fossil tigers from the Russian Far East were somewhat comparable to the Korean tigers in term of size.

Maybe these fossil tigers were likely more linked to the historical Korean tigers than to the Manchurian tigers?

Interesting suggestion, Grizzly. I've been thinking about this one for a long time. Although a good answer is all but impossible, we could give it a try.


1 - QUOTES FROM THE SUMMARY OF THE BARYSHNIKOV ARTICLE

1a - " ... Five AMS C clades were made on the tiger bones. They ranged between 34 300 and > 40 000 years. Six AMS C dates were made on the hyena bones. They ranged between 34 510 and 48 560 years. This means that the layer in which the bones of tigers and hyenas were found was deposited in a Late Pleistocene warm phase (MIS3) ... " (pp. 01);

1b - "... A recently conducted mitochondrial analysis sorts out recent populations of Panthera tigris into six clades or subspecies (Luo et al., 2004). The reduced genetic variability within the grouping of Amur tiger, P. tigris altaica, could be a result of the postglacial colonization of the region (a) and a population bottleneck that happened not earlier than 10 000 years ago (b). The genetic similarity between the Caspian tiger, P. tigris virgata, and the Amur tiger, P. tigris altaica, suggests the Russian Far East was colonized from Central Asia (pp. 04);

1c - " ... Another analysis embracing morphological, ecological, and molecular data revealed a ... marked overlapping of characters between recent tiger populations as well as their low genetic variability (Wilting et al., 2015). As a result of this analysis, it was proposed to accept only two subspecies: Panthera tigris tigris (Linnaeus, 1858) in the continental part of Asia and Panthera tigris sondaica (Temminck, 1844) in the islands of Sumatra, Java and Bali ... " (pp. 05);

1d - " ... The lack of marked genetic differences between continental tiger populations can be explained by the late migration to northern Asia in the Holocene. Tigers presumably migrated to northern Asia on two occasions: during the Late Pleistocene warming (MIS3) and during the warm Holocene interglacial. They (tigers) most probably were not present in northern parts of Asia before approximately 18 000 years ago ... " (pp. 05).

1e - " ... The teeth of the fossil tigers ..., and the m1 in particular, are larger than those of Panthera tigris altaica. The lower carnassials of recent tigers, however, seem more advanced than those of Late Pleistocene tigers ... " (pp. 05).

1f - " ... The ... fossil ... ulnas do not exceed the size of the ulna in the recent P. tigris, whereas this bone is noticeably larger in P. spelaea and the recent P. leo ... " (pp. 03).    

1g - " ... All bones found (tibia, os calcaneous, os talus and a few fragments of metatarsal 2,3,4 and 5) are smaller than those of P. spelaea and sizewise correspond to those of the recent P. tigris ... " (pp. 03).


2 -  PRELIMINARY CONCLUSIONS

2a - The tiger bones found in the caves in the Russian Far East are 35 000 - 50 000 years old. This means that the layer in which they were found was deposited during warm Late Pleistocene warm phase.

2b -  The reduced genetic variability within the grouping of Amur tiger was a result of the postglacial colonization of the region (a) and a population bottleneck that happened not earlier than 10 000 years ago.

2c - The genetic similarity between the Caspian and the Amur tiger suggests that the Russian Far East was colonized from Central Asia.

2d - A recent analysis based on morphological, ecological and molecular data showed a marked overlapping of characters between recent tiger populations and low variability of the different local populations or subspecies. For this reason, Wilting proposed to distinguish between mainland and island tigers

2e - Tigers only migrated to northern Asia during the Late Pleistocene warming and the warm Holocene interglacial.

2f - The bones of Late Pleistocene tigers found in the Russian Far East suggest they were similar in size to recent tigers living in that region (Panthera tigris altaica). Bones and mandibles of male cave lions, Panthera spelaea, were larger.


3 - OTHER STUDIES 

Based on what was known, I wrote a summary about tiger evolution in 2014. This paragraph has a few quotes we could use.
  
3a - The first true tiger fossils, about 1,6 million years old, were found in Ci Saat and Trinil deposits in Java. They are considered remains of the Trinil tiger, Panthera tigris trinilensis (pp. 01).

3b - P. tigris trinilensis spread from Java to mainland Asia in the early Pleistocene, when the Sunda Shelf was connected to mainland Asia. This is the first wave and it is assumed P. tigris trinilensis ... replaced the more primitive Chinese tiger (pp. 01).

3c - A new tiger evolved in mainland Asia in the Middle Pleistocene. Panthera tigris acutidens, the Wahsien tiger, replaced P. tigris trinilensis (pp. 01).

3d - P. tigris acutidens reached Berengia. Unlike the cave lion P. spelaea spelaea, it wasn't able to cross this land bridge. In the south, during the last stages of the Pleistocene, P. tigris acutidens replaced P. tigris oxygnata, which had replaced P. tigris trinilensis, and evolved into P. tigris soloensis, possibly the largest tiger ever (pp. 01).

3e - About 75 000 years ago, the Toba erupted. The eruption destroyed large parts of Sumatra and had a profound impact on climate. The change in conditions resulted in many extinctions and population bottlenecks. In mainland Asia, tigers all but disappeared. They only survived in northern Indochina and southern China. This population evolved into the recent tiger P. tigris. From Indochina, they spread to northern and western China, reaching the Caspian by using the Silk Road less than 10 000 years ago (Driscoll et al., 2009). From there, they spread west and east. Just before they reached the Silk Road, tigers colonized India about 12 000 years ago (pp. 01-02)   

3f - The land bridge between mainland Asia and the Sunda Shelf existed until approximately 50 000 years ago. Mainland tigers going south and Sunda tigers going north met in Sumatra, where they mixed and evolved into P. tigris sumatrae. When the land bridge disappeared, Sumatran tigers became separated. As a result of the long separation, they, according to some, developed into a different species: Panthera sumatrae (pp. 02).


4 - BIOGRAPHICAL CHANGE IN THE TIGER, PANTHERA TIGRIS (A.C. Kitchener and A.J. Dugmore, 1999)

4a - " ... The number of tiger subspecies is a major conservation issue that is difficult to resolve owing to small fragmented extent populations and limited historical samples in museums, which compromise the rigour of both molucular and morphological taxonomic studies. Rather than considering a static taxonomic approach to geographical variation in the tiger, we consider the changing biogeographical range of the tiger through the last glacial-interglacial cycle, based on habitat associations of modern tiger specimens records, and environmental reconstructions from the last Glacial Maximum (LGM; approximately 20 000 years before present (B.P.)). We regard this cycle as representative of the numerous glacial cycles that span the evolutionary history of the tiger since its appearance in the fossil record about two million years ago, thereby giving a time-deep perspective.

The key issue is to determine the extent to which ancestral populations of the tiger were geographically isolated. If no ... isolation is likely, and gene flow between tiger populations could be maintained until modern times, than diagnostically distinct populations could not have evolved.

Our reconstructions show that only two tiger populations were likely to have experienced significant geographical isolation from the main distribution; these were to the west of Tibet (during the LGM) and on Japan (throughout the glacial cycle). In addition, the LGM is likely to have seen the partial separation of peninsular Malayan and Sunda tigers from mainland populations. From a biographical perspective it seems probable that only three contemporary populations were sufficiently separated for the evolution of distinct populations, which can be regarded as subspecies or evolutionary significant units. Therefore, most variation in modern tiger populations is probably clinal, which has importasnt implications for future conservation both in the wild and in captivity ... " (abstract).

4a - Two maps suggesting that the Russian Far East wasn't colonized by Caspian tigers spreading east about 20 000 years ago:

*This image is copyright of its original author

*This image is copyright of its original author

       

5 - TIGERS IN NORTHERN ASIA

5a - Baryshnikov wrote that the bones found in the caves in the Russian Far East in the sixties and seventies of the last century are roughly 35 000 - 50 000 years old. He also wrote that Late Pleistocene tigers, although about similar in size, had slightly larger teeth than the recent tiger living in that region, P. tigris altaica. Both were smaller than cave lion males, P. spelaea.    

5b - Based on the studies referred to above, Baryshnikov concluded that tigers only colonized northern Asia in the last stages of the Pleistocene or in the Holocene, most probably no before 18 000 years ago. This means that the tigers living in the Russian Far East 35 000 - 50 000 years ago had come from the west or east. As there is hardly any difference between Caspian and Amur tigers, most assume that the Russian far East was colonized by Caspian tigers going east. Kitchener and Dugmore (1999), however, concluded it's unlikely that Caspian tigers reached the Russian Far East before the Holocene. Based on the maps above, this region, in their opinion, had to be colonized from the south. Japan and Korea, however, can't be completely excluded from the equasion. 

5c - Different studies suggest that tigers in northern Asia (P. tigris virgata, P. tigris altaica and P. tigris amoyensis), are different from tigers in southern Asia.

   
6 - CONCLUSIONS

6a - In his article, Baryshnikov discribes 211 tiger bones of 6 individuals found in a number of caves in the Russian Far East. The bones were found in layers that were deposited 35 000 - 50 000 years ago roughly. We're talking about the Late Pleistocene, that is. The bones are not very different from the bones of recent tigers living in the Russian Far East; teeth a bit more primitive and a trifle larger, but that's about it.

The same Baryshnikov, in the same article, says northern Asia was only colonized by tigers in the last stages of the Pleistocene and, in particular, the Holocene. There were no tigers in northern Asia before 18 000 years ago, that is. But he found overwhelming proof of Pleistocene tigers living in the Russian Far East well before that mark. So what's going on here? And where did these Late Pleistocene tigers in the Russian Far East come from? 

From the west, Driscoll said. Caspian and Amur tigers are just about one and the same. Could be, but Kitchener and Dugmore argued it's very unlikely that Caspian tigers reached the Russian Far East before, say, 20 000 years ago. 

The question still is where the Late Pleistocene tigers in the Russian Far East came from. Based on the maps of Kitchener and Dugmore, China seems to be the best option. But Japan and Korea can't be completely excluded. About 20 000 years ago, Japan still had tigers. The conditions, in fact, were excellent. Japan tigers are present in all maps.

In short. What I found is unclear, if not contradictory.

6b - Based on what I read, my guess is that tigers did reach northern Asia and Japan in the middle Pleistocene during a warm phase. According to Kitchener and Dugmore, Japan was almost completely colonized about 100 000 years ago. When the ice returned, tigers in central and northern parts of Asia most probably moved to the southwest (the Caspian region) and the southeast (northern China, the Russian Far East and Japan). When the conditions improved once more, Caspian tigers moved to the east and Amur tigers (tigers from Japan, Korea, the Russian Far East and northeastern China) moved west. Must have happened more than once until 15 000 - 20 000 years ago.

6c - In the Holocene, the human population exploded. Japan tigers were perhaps the first to go. This was after Japan had become separated as a result of rising sea levels. In tigers, separation always results in a loss of size. My guess is that Japan tigers were smaller than average. Korean tigers were next. Although they survived in densely forested and elevated regions until the early decades of the 20th century, they too became isolated over time. Large individuals were shot until the end every now and then, but the isolation must have had an effect on size. The region between the Caspian and the Russian Far East had breeding tigers, but Heptner and Sludskij and V. Mazak concluded that the conditions were unfavourable. In the last three centuries, this region must have seen tigers on the move. When fire-arms were introduced, these travelers disappeared.

Manchuria and the Russian Far East offered the best chances for tigers. As the conditions in Manchuria in particular were good for a long time, it is no surprise that tigers, sizewise, reached a peak in this region. If we add that Manchuria and the Russian Far East were somewhat out of reach for both the Chinese and the Russians for quite some time (no large cities, no agriculture and a harsh climate), it is no surprise that they did quite well until the last decades of the 19th century. When Japan had occupied Korea and Manchuria, it was game over. Only after they had left, the tiger situation, thanks to Kaplanov, got some attention.

The loss of size of Amur tigers could be a result of a lack of gene exchange mainly. There are no tigers left in Japan, Korea, Manchuria and the Altai Mountains. Amur tigers are on their own, that is. If we add a population bottleneck between 1900-1950 (resulting in inbreeding), 60 000 hunters (resulting in competition and prey depletion) and habitat destruction (the Russian Far East has many natural resources, which resulted in new roads offering plenty of opportunities to poachers), it is no wonder that they struggle. Amur tigers now are protected, but views can change overnight.

6d - If I would have a say, I would recommend a new study based on literature only. The first task is to eradicate contradictions and get to a number of conclusions supported by all. Preconceived ideas should be removed and everything we have should be invested in establishing and securing a number of large reserves closed to the public for quite some time. Russia and northeastern Manchuria seem to be the best options, but central parts of China also offer opportunities. In 2011, it still had a small number of wild tigers.


7 - FUTURE

7a - During the last weeks, I found quite a bit on Amur tigers, tigers in northern parts of China and tigers in central and southeastern China. The aim is to start with Amoy tigers (southeastern China) and slowly move north. 

The Chinese tiger, Panthera tigris amoyensis, had different faces in different parts of China. Although large and robust individuals have been shot in the south, Amoy tigers were less robust than tigers in central parts of China. Tigers in northern China, as far as I know, always have been quite large. In the recent past, Manchuria and the southwestern part of the Russian Far East could have been a region where tigers from different regions have met and bred.

7b - This thread has quite a few links to interesting articles and a number of good posts about tiger evolution. Posts 740 to 790 are recommended for those interested in evolution. Reply