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RE: ON THE EDGE OF EXTINCTION - A - TIGERS (Panthera tigris) - peter - 07-05-2015
TIGER EVOLUTION - SUMMARY
After reading the Balkenhof, Fickel, Kramer-Schadt and Kitchener article on intraspecific variation in tigers, I was ready to respond. When I tried to find my last post, however, I was amazed at the barrage of information I found. It's clear that some of us are interested in tiger evolution and taxonomy. My guess is the debate will continue for some time.
As to tiger evolution and taxonomy. In spite of the different views, a few things seem to stand out:
a - All agree there was a Pleistocene population bottleneck about 75 000 - 100 000 years ago. Many think it was related to the Toba eruption. As the results of the eruption are still visible in many mammals, the conclusion is it must have been devastating.
b - Although interglacial periods were not uncommon in the Pleistocene, the climate definitely changed just before the Holocene. About 10 000 - 20 000 years ago, global warming resulted in rising sea levels, expanding forests, more mammals (and herbivores in particular) and new chances for big carnivores.
c - The evolution of mammals ultimately seems to be related to climate. They expanded when opportunities were offered and suffered or disappeared completely when the ice returned. Seen from a distance (thousands of years), evolution is characterized by waves of expansion and periods of destruction.
d - Tigers might have evolved a few million years ago somewhere in southern China. During periods of global warming, they expanded both to the south and the north. Although remnants of the types which developed in these regions might have survived long periods of destruction, there's no question they are different from modern tigers. Modern tigers again spread from China.
e - When sea levels rose, Sunda tigers became isolated. Same perhaps, but to a lesser extent, for Malaysian tigers. The local races in mainland Asia most probably were a result of human expansion, meaning tigers were pushed to inaccessible and isolated areas not connected to others areas that had tigers. After the introduction of fire-arms, tigers were actively hunted and often locally destroyed. The answer to the question whether they are (or were) subspecies or not largely depends on the definition of what a subspecies is. All mainland tiger subspecies probably developed in the last 20 000 years.
f - Conservationwise, the debate about (the status of) subspecies doesn't seem to be decisive in that it is known that captive tigers of different subspecies quickly interbreed. Wild animals of different subspecies probably also interbreed and adapt to local circumstances, resulting in local types sooner or later. Judging from what is seen in isolated regions like the Sunderbans, where tigers dramatically changed in less than two centuries, my guess would be sooner. Another, indirect and partly artificial, example would be the experiment with China tigers in South Africa. In a few generations, they adapted to the local conditions by increasing in size. Same, but the other way round, in regions in which tigers are (were) severely hunted.
Manipur is directly south of the Naga Hills, where tigers were decidedly smaller than those in other parts of India. But half a century earlier, males well exceeding an average Naga Hills male were not uncommon in that area. Manipur, especially the eastern part close to Burma (Myanmar), was wild country, whereas the Naga Hills had many estates (tea). Big cats apparently quickly adapt to local circumstances and it often shows in size. Isolation and stress (as a result of habitat destruction and poaching) often result in miniature tigers in a few generations only. If they don't decrease in length, they, like in eastern Russia, lose weight. The opposite also is true.
g - Although Kitchener's suggestion regarding the development of local types (cline) is more accurate than the suggestion of others (tiger subspecies are clearly different from others), it has to be said that the skulls of the subspecies I saw suggest a cline would be an oversimplification. If size only would be used as a criterium, he is close, but there often are marked differences between different subspecies. Most of these haven't been quantified. As no quantification in science equals absence, they officially do not exist. But they do and can be seen at a glance. A good topic for a debate, I think.
RE: ON THE EDGE OF EXTINCTION - A - TIGERS (Panthera tigris) - brotherbear - 07-05-2015
To the best of your knowledge ( those interrested ) what became of the lions and tigers which found their way into North America during the Pleistocene? I would suppose that the lions were Asiatic.
RE: ON THE EDGE OF EXTINCTION - A - TIGERS (Panthera tigris) - GrizzlyClaws - 07-05-2015
The only two Panthera species that made their way to the heartland of America were Panthera atrox and Panthera onca, but Panthera spealea and Panthera tigris (based on few fossil remains) stranded in Alaska for some odd reason.
I assume that the eastern part of North America is suitable for tiger's habitation, while the western part for lion.
As for South America, the northern part is dense jungle, thus suitable for tiger. And the souther part is open plain, thus for lion.
RE: ON THE EDGE OF EXTINCTION - A - TIGERS (Panthera tigris) - tigerluver - 07-26-2015
Have we discussed Luo et al. (2004)? This study also uses the tiger genome, but concludes that there is much more difference than Kitchener's interpretation. Like I've said before, molecular phylogeny, or even morphological phylogeny, is very open to author bias in its interpretation.
http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.0020442
RE: ON THE EDGE OF EXTINCTION - A - TIGERS (Panthera tigris) - GrizzlyClaws - 07-26-2015
It is quite intriguing that some South China tigers cluster with the Indochinese tigers in the mtDNA, while some others cluster with the Sumatran tigers.
The South China tiger in my opinion is the true relic, and they likely carry the gene of the prehistoric tiger as well.
RE: ON THE EDGE OF EXTINCTION - A - TIGERS (Panthera tigris) - tigerluver - 07-26-2015
The sample size is probably another major problem with analyzing the South China tigers phylogenetic position. We have plenty of samples from the other species, but the South China form is just about extinct. That cause a raw sample problem, as we have less actual samples to test. On a population genetics scale, a small (very small in this case) will not only lead to a genetic bottleneck, but there will also be genetic drift (the gene pool, by random chance, changes composition in a given direction), making the remnant population not a great representative of the true population genetic makeup.
Had we had more South China tigers, maybe we could get its true phylogenetic position determined better, rather than having conflicting studies on its positioning.
RE: ON THE EDGE OF EXTINCTION - A - TIGERS (Panthera tigris) - peter - 07-27-2015
PLANNING TIGER RECOVERY: UNDERSTANDING INTRASPECIFIC VARIATION FOR EFFECTIVE CONSERVATION (Wilting et al., 2015)
The link to this article was posted by Tigerluver (post 724). This post has an overview of the most important conclusions.
a - INTRODUCTION
The first sentence is as good as it gets:
" ... Fewer than 4000 tigers inhabit the forests of Asia - a historically low number. These tigers occupy only 7% of their estimated former distribution range, and 70% of them inhabit 42 source sites, which occupy only 0,5% of their historical range ... " (pp. 1).
The second and third compare:
" ... Almost $50 million is spent annually by range countries, non-governmental organizations, and private donors on the conservation of wild tigers. This amount has massively increased since the launch of the World Bank's Global Tiger Initiative (GTI) in 2008. No other threatened species commands such resources and attention from the international community ... " (pp. 1).
The fourth also is a beauty:
" ... A precondition for a successful tiger recovery and global tiger management ... is a consensus on the number of tiger conservation units (that is, subspecies, evolutionary significant units (ESU's), ecotypes, or management units) because active interventions, such as translocations or releases of captive-bred tigers, will presumably become more important in the future for reversing the decline of wild tigers ... " (pp. 1).
It doesn't stop there:
" ... Despite repeated previous efforts to unravel tiger diversity and define conservation units in terms of subspecies, results were often contradictory and no consensus has been reached so far. Up to nine subspecies of tigers are currently recognized, three of which are already extinct and a fourth probably only survives in captivity ... " (pp. 1).
What is their conclusion on the efforts to 'unravel' tiger diversity?
" ... In summary, previous studies often used small sample sizes and used either only morphological characters or only molecular markers to characterize subspecies. The two approaches have only occasionally been combined in a superficial way. Consequenlty, the validity of some or all subspecies remains a matter of debate ... " (pp. 1).
I wouldn't get to devastating, but it is close. Research- and subspecieswise, the picture is quite gloomy. Is there not a glimmer of hope then? No light somewhere in the sea of darkness? Of course there is:
" ... Here, we present the most comprehensive analysis to date of molecular, morphological (craniodental and pelage data), and ecological (climate, habitat, and prey data) characteristics of all nine putative tiger subspecies. We show that with a comprehensive multi-trait data set, only two subspecies (one consisting of two management units) receive robust support. We conclude with a discussion of appropiate conservation strategies, and propose a scientifically sound and more pragmatic approach to reverse the tiger's population decline ... " (pp. 3).
This is a one-minute course in introductions, I think. You first present the subject of many studies, the poor tiger. The reader sees a gloomy picture in that 70% of the tigers left today inhabit 0,5% of their historical range only. Terrible. Then the World Bank's Global Tiger Initiative is presented. The conclusion is no other threatened animal receives as much dollars as the tiger. Did the support had effect? No. How come? No clear management strategy, which is a result of a difference of opinion on the number of tiger subspecies. How develop an effective strategy when there is no agreement on the number of subspecies? The answer is you first dismantle all studies on subspecies and then present the solution (two subspecies) in a new article. Problem solved. And full marks.
A cynical appreciation, some might think. The answer is no. The introduction is well written, the problems mentioned are very real and the result is wild tigers still walk the edge. Something needs to change and it has to change real fast. Would limiting the number of subspecies help? In order to answer that question, a few issues need to be addressed.
RE: ON THE EDGE OF EXTINCTION - A - TIGERS (Panthera tigris) - tigerluver - 07-27-2015
The main issue with the Wittig study is that it seems the authors already have the interpretation of tiger subspeciation before the actual results, based on the fact that some of the authors have already proposed this structure.
Regarding conservation, I feel the issue lies more in the government initiative than the tiger taxonomic debate as the paper proposes. In the end, each country is responsible for the tigers within its borders, regardless of subspecies. Tiger subspecies isn't even very debate by most, including conservationist despite the clinal variation proposal dating back to the beginning of this century.
RE: ON THE EDGE OF EXTINCTION - A - TIGERS (Panthera tigris) - peter - 07-27-2015
Yes, although mentioned at the end of the list, I saw Kitchener as well.
RE: ON THE EDGE OF EXTINCTION - A - TIGERS (Panthera tigris) - GuateGojira - 07-27-2015
So, according with you guys, the authors are running in circles, as they already have a preconceive idea and the "analysis" is only corroborating it, instead of searching new conclusions.
Somehow, I feel compelled to backup they results, as if we actually face the facts, the traditional "subspecies" are based in practically nothing more than two or three specimens, only the Indochinese tigers were examined by more than 20 specimens. Besides, the clinal variation can be, at some point, less dramatic than what Mazák's size table can suggest.
For example, Amur-Bengal-Caspian tigers are/were of the same size, yes, I am pretty sure than the Caspian tiger was larger than the few available skulls suggest. I mean, check how few skull are of this population, but now check the photographs, there are specimens as large as the largest Bengal and Amur tigers. So, in the three more distant populations of mainland tigers (the "three kings"), they present the same size: c.200 cm in head-body, c.100 cm in shoulder height and a weight of 240-260 kg.
Now, let's go to the southeast of Asia, in Indochina and South China, those are classified as smaller animals, specially those from China. However, AGAIN, check the sample sizes. There only a dozen of skulls from China (males and females included) and another few from the entire Indochina area. However, if we see the documents of Kitchener (1999) and Kitchener & Yamaguchi (2010), the largest "Indochina" tiger skulls came from Malaysia, an area that is now popularly know for they "small" tigers. If we get the few data of China, those tigers seems small, but like I say, the sample is small, however, the largest specimen recorded is about the same size and weight than an average Amur tiger (190 cm in head-body and 190 kg), suggesting that probably, with more specimens, that clinal variation could be shown more clearly, with an "up" in the center of China, close to Manchuria and a "down" close to Indochina and again another "up" close to Thailand. Finally, in Indochina, some authors (I forgot they names, but @peter probably remember them) stated that the tigers in that area weighed up to 220 kg and there is the report of Baze of a giant tiger weighing 259 kg (570 lb) in this area, just like the heaviest Indian tigers. Probably it was a freak, but it shows that in the old days, the tigers in that area, with more prey, were as large as the "three kings".
Moving to Malaysia, those tigers were not the "dwarfs" that are popularized by Dr Kawanishi. He based his statements in two males that were "estimated" at 110 and 130 kg respectively, however when we see the table published in a conservation program document of Malaysia, we see that the size of those specimens are by no way correlated with those weights and in fact, the table itself stated that no weight was real, all were estimations as any scale was available at that time. The old records from the area present tigers as large as an average Indian specimen, and although Locke estimated them at no more than 160 kg empty, we know that body mass is affected more by prey availability than for "sub-speciation".
Finally, if we stay in the Indian subcontinent only, there is some variation if body mass, but the size remain the same. All tiger populations, from the entire Terai region, central India, and both west and east Ghats, tigers measure between 260-310 cm in total length, with no variations and no "ups" or "downs". In body mass, Terai tigers seems heavier, but in fact, Central Indian tigers are also very large with specimens weighing over 255 kg. The only Bengal tigers that weight less than that are those of Sundarbans and the Naga Hills, however those in the last area are based in very small samples and those from Sundarbans (modern ones at least) are based in frail specimens, some of them even unable to hunt. However, all these populations are "Bengal" tigers, and separate them in "subspecies" will be a silly mistake.
So, as we can see, there are very few variations in the mainland tigers and it seems that all populations were connected until the human intervention. Tigers can travel as far as 1,000 km, so male tigers from different areas could propagate they genes in distant areas beyond the "traditional" boundaries of the "subspecies". When only Mitochondrial DNA is used, we most take in count that female tigress are less prone to travel great distances, so the female genetic diversity is more focused in areas, and those can be interpreted as "subspecies-area cores", however, if Nuclear DNA (from males) is studied too, we could see more variations, as a young Bengal tiger could travel as far as the boundaries of the Indochina population and its sons even deeper. Only human presence stooped the tiger distribution, cutting the Amur-Caspian tiger population and later (as show by @GrizzlyClaws), the great China wall separated the China tigers from those of the Amur region, all this in historic times, at less than 200 years in some cases.
Mainland tigers have size peaks in the Amur, Caspian and Terai region, some medium points in the forest areas of South India, Indochina and Central China, and low values in lower Indochina, Malaysia and the China coastal areas. This, from my point of view, is a perfect clinal situation, and the differences in the skulls are just adaptations to the habitats, just like the modern humans skulls (again, check the skulls of the Mayan, Australian, European, Indian or the South of Africa, all natives, and all look different, but all are Homo sapiens).
On the islands, there is clear evidence that Javanese tigers were slightly larger than Sumatran ones, but this is based in the fact that the Javanese tigers had a best prey base than those of Sumatra. And about the Bali, we only have 9 skulls and a few skins, so we can't make clear conclusions and based in the last available pictures of Bali specimens, we can clearly say that the conclusions of Mazák that this tiger population was "small", are incorrect and should be discarded as "facts" and labeled just as "opinions" in his days. I suspect that, in the best days, Sumatran and Javanese tigers were of the same size, with a slight advantage for those of Java, meanwhile Bali tigers were probably smaller in comparison, but not the dwarfs that are popularly stated. I guess that Sundarbans tigers are/were the real "smaller-group" of tigers.
This is my appreciation, based in a quick analysis. Some points can be incorrect, but I bet that my appreciation is more conclusive than the old conceptions. However, like @tigerluver said, the concept of "subspecies" depends of the investigator, and this a real problem. Dr Kitchener proposed the "75% rule", but it seems that for other people, like Luo (in 2004 and 2010), a little genetic difference is enough to erect a new "subspecies", ignoring all the taxonomic rules and avoiding to provide AT LEAST one Holotype for her claims.
From this evidence, I think that the proposal of 2 subspecies, with 3 conservations units, for modern tigers, is accurate from a Biological point of view.
RE: ON THE EDGE OF EXTINCTION - A - TIGERS (Panthera tigris) - peter - 07-27-2015
Excellent appreciation, Guate. We could talk a long time about subspecies, definitions and sound classifications, but in the end I agree with the writers of the article in that it is five to twelve in many countries. Something needs to be done and one of the things biologists can attribute is simplicity. I also think the proposal to rewild captive tigers in some regions is more than just an option.
Tigerluver, however, has a point in that some biologists and zoologists seem to be navigating towards preconceived ideas. It also is a fact that the samples used to get to statements often are way below the threshold needed. I still wonder why nobody even attempted to get to a decent sample. It can be done if you're prepared to visit as many museums as possible. One could also try to contact private collectors. My guess is many would be willing to cooperate.
Although I do not doubt the validity of the nine subspecies mentioned in the article recently discussed, we also need to recognize three facts:
a - Today's tigers evolved after the Toba eruption. In evolutionary terms, it is a recent species.
b - Captive tigers of different subspecies readily interbreed.
c - Wild tigers rapidly adjust to changing circumstances, both in size and behaviour.
Tiger conservation doesn't have to be impaired because of a lack of tigers or because of changing conditions, that is. Not in mainland Asia. The key to conservation isn't simplicity, more studies or more money, but politics. The only country willing to commit, as far as I can see, is Russia and it shows. Not only in more tigers, but in more territory, habitat improvement and legislation. Not saying there's no commitment in other countries, but not at the level of central government. And when it does, it doesn't last long enough to get to results. In most of Asia (Indonesia included), the elites see profits and those who vote want work and a decent income, not a wild tiger lurking around the corner. The outcome of the development that has to be expected would be habitat destruction and guess what.
How chan ge the tide? In what way can large organizations help? How use the money available in the correct way? For now, I would say leasing wild country seems to be the best option. You lease suited parts (long-term contracts only), turn them into reserves, pay for all expenses (management, rangers and equipment) and, in this way, keep some kind of control. A part of the reserve will have to be used to attract visitors and generate both goodwill and some money. It would compare to the period of colonisation in some ways, but the benefits, for all involved, would outweigh the disadvantages, especially in the long run. Preserving islands of wild country and pristine forests wouldn't suit unrestricted gene flow, but chances are tigers would survive one more century.
RE: ON THE EDGE OF EXTINCTION - A - TIGERS (Panthera tigris) - tigerluver - 07-28-2015
Modern tiger research has forgotten about the reports of populations in Borneo and maybe even the Philippines, at least they're not a point for discussion. Looking at the Sunda shelf, I took it for granted that tigers inhabited Borneo based on the current database. But a paper questioned the consensus but also pointed out supporting evidence, and I've attached it (Meihaard 1999).
Regardless, in my opinion, tigers should have at some point been on Borneo based on the findings a tiger on Palawan, a region between Borneo and the Philippines. Piper et al. (2008) cites two fossils dating from only 12 kya. The bones (phalanx) were slightly larger than the comparitive modern Indian and island tiger fossils. Interestingly, Javan tiger phalanx are slightly bigger than the Indian specimens compared. Although, the gender of the Indian tigers are unknown, and they may simply be females. From this, I think tigers that were of the P. t. sondaica subspecies likely survived until very recently on Borneo and the Philippines. Two fossils show something slightly larger than the Javan tiger, assuming the phalanx proportions were like the Javan form's oddly large paws.
I've also attached the Palawan paper. What do you guys think of the papers analyses?
RE: ON THE EDGE OF EXTINCTION - A - TIGERS (Panthera tigris) - peter - 07-28-2015
PLANNING TIGER RECOVERY: UNDERSTANDING INTRASPECIFIC VARIATION FOR EFFECTIVE CONSERVATION - II
2 - TIGER SUBSPECIES
a - Previous studies
In the last two decades, quite many articles on tiger evolution and subspecies have been published. Although each of them is interesting, Wilting and his collegues have a point in that most are based on smallish samples. Furthermore, the two most used approaches (morphological characters and molecular markers) were only combined at a superficial level. For this reason, the result is tentative at best.
Table 1 - Current tiger subspecies classification:
*This image is copyright of its original author
b1 - Present study
Wilting et al. conducted a molecular analysis of all nine putative tiger subspecies. The conclusion was that
" ... modern tigers contain substantially lower genetic diversity than other pantherinae or Southeast Asian cats. The demographic reconstruction revealed a population decline around 80 thousand years ago, followed by a late Pleistocene expansion. This suggests that modern tigers succumbed to rapid environmental changes after the Toba super-vulcanic eruption ... in northern Sumatra. The impact of this eruption has been linked to population bottlenecks on other mammals such as humans, orangutans, and clouded leopards. Thus, tigers may have only survived in a single refugium outside the region of ash-cloud fallouts. The ancestral position of haplotype AMO1 suggests the presence of such a refugium in or around southern China ... " (pp. 3).
According to Wilting and his collegues, the presence of tiger fossils dating back 2,55 million years from throughout the the current tiger's range from northern China to Java, Shri Lanka, and Japan (a) as well as the widely accepted view that the tiger's high morphological variation across its wide geographical distribution was an adaption to local habitats (b) prevented a broader discussion of the Late Pleistocene population decline.
There is, however, no question that:
" ... the low molecular as well as morphological variation ... strongly favors the scenario that ancestral Pleistocene tigers became extinct in large parts of their former ... range and were replaced by modern tigers recolonizing large parts of Asia as recently as the Late Pleistocene ... " (pp. 3).
b2 - Conclusions
Molecular analysis, morphological characters (skulls and skins) and ecology enable 3 main conclusions:
1 - Modern tigers evolved after the Toba super eruption about 73 500 years ago (Late Pleistocene). In evolutionary terms, modern tigers are 'younger' than all other roaring cats.
2 - Modern tigers evolved from China tigers (Panthera tigris amoyensis), who survived the Toba super eruption. From China, they spread south (Sunda Shelf and Malaysia) first. Western (and central) parts of Asia were occupied later, well before northern parts of Asia were reached. The most recent wave could have been directed at northeast Indochina (Panthera tigris corbetti), and not Manchuria (Panthera tigris altaica).
3 - Modern tigers can be divided into 2 groups (or subspecies): island tigers and continental tigers. The last group can be divided into 2 sub-groups: a northern consisting of P.t. virgata, P.t. altaica and P.t. amoyensis and a southern consisting of P.t. tigris, P.t. corbetti and P.t. jacksoni.
For those interested in details.
3a - Craniodental morphology. Male (not female!) skulls of northern and eastern tigers (P.t. altaica, P.t. virgata and P.t. amoyensis) are distinct from those of other continental tigers.
3b - Pelage morphology. Skins of northern tigers (P.t. altaica and P.t. virgata) are distinct of those of other continental tigers.
3c - Ecology. Northern tigers (see above) were clearly separated from all other tigers. Southern tigers, except, Malayan tigers, clustered together.
3d - Molecular population structure. Amur and Caspian tigers grouped together, whereas Bengal and Indochinese tigers form distinct groups. Malayan tigers, although genetically separated from other continental tigers, are the only clade with two clear subclades.
b3 - Can continental tigers be divided into separate subspecies?
" ... None of the six putative continental subspecies could be consistently distinguished by morphological or ecological characters, because they overlapped greatly ... Therefore, our data reject the taxonomic division of continental tigers into six subspecies. Instead, they should be merged into a single subspecies, which shows only minor local ecological adaptation and differentiation by distance ... " (pp. 5 and 7).
b4 - The difference between Bengal and Javan tigers at a glance
Take notice of the differences in condylobasal skull length between both subspecies. In island tigers, extremes have been removed. In continental tigers, on the other hand, extremes (in both directions) are present. Sizewise, island tigers not only are smaller. They also are much more uniform:
*This image is copyright of its original author
In words:
*This image is copyright of its original author
b5 - Summary
*This image is copyright of its original author
3 - CAPTIVE TIGERS
" ... Our results mostly support current conservation management of captive tigers ... Our results demonstrate that the current breeding programs accridited by the World Association of Zoos and Aquariums (WAZA) could be extended by inclusion of many of these supposed hybryds because southern continental tigers do not need to be managed according to their hitherto conventional subspecific classification ... " (pp. 8).
" ... Our recommendations assist in the maintenance of genetic diversity and are consistent with recent findings, according to which every tiger, both wild and captive, is important as a potential reservoir of genetic diversity of the species. The seperate breeding of Indochinese, South Chinese, and Malayan tigers is likely to be unsustainable because only few founder individuals were available - for instance, only six individuals for South Chionese tigers. In contrast, both the northern continental tiger management units and the Sunda tiger subspecies have been traditionally maintained in seperate breeding programs. Their number of founders were much higher; several hundred individuals are currently part of international breeding programs. For Sumnatran tigers, the international zoo community led by WAZA has even succesfully established a Global Species Management Plan. The seperate conservation breeding and management of these units is supported by our results and should be continued ... " (pp. 9).
4 - CONCLUSIONS
Pocock (1929) saw his proposal on tiger subspecies as a working hypothesis. Over the years, it was refined and extended. In the nineties of the last century, new methods were introduced to get to more insight. Although the attempts to get to a more accurate classification never met with universal approval, it became increasingly clear that Pocock's upgraded proposal had run its course. The question was not if it would be fundamentally changed, but when. And how.
This year, it was finally replaced by the proposal of Wilting and his collegues. Remarkable, but it wasn't done in a spectaculair way in that their findings are not that different. The difference with most other attempts is Wilting and his collegues combined different factors. More important is that the findings were interpreted in a different way. One could disagree with their conclusions, but not with the methods used. Wilting and his collegues found proof for local types, but concluded the amount of overlap between them is too pronounced to claim the title of subspecies.
One could use their results to claim the opposite and adjust the decisions regarding conservation. This, as they argued, would backfire in that most of the five remaining subspecies would be doomed because of a lack of tigers. Furthermore, a strict classification would result in the loss of many captive tigers in that they won't be used to rewild or to breed.
As to those who have a different opinion. I do not doubt that a period of, say, 20 000 years is enough to get to significant differences between local tiger populations, especially if they inhabit isolated regions. The skulls and skins I saw underline there are significant differences between different local populations. Same for body dimensions. It is, on the other hand, also known captive tigers of different subspecies readily breed. They also quickly adjust to new conditions.
Furthermore, one has to remember that the time of natural conditions affecting morphology is largely past and gone. In the period that tigers recolonized Asia from China, humans had zero influence on the natural world. Animals, therefore, adapted to natural conditions only. The results, skull-, skin- and dimensionwise, really reflected the local conditions. When humans multiplied and fire-arms spread, gene flow was severely restricted. In a very short period of time four subspecies were exterminated. As the other five are close to the edge, Wilting and his collegues developed a classification that could, conservation and managementwise, perhaps help to change the tide.
A gross oversimplification or a life-saver? I thought I saw desperation as well, but the situation is desperate. Wild tigers probably only stand a chance in isolated pockets in India, Malaysia, Thailand and Russia. Maybe pragmatism isn't a bad idea.
RE: ON THE EDGE OF EXTINCTION - A - TIGERS (Panthera tigris) - peter - 07-28-2015
(07-28-2015, 01:42 AM)'tigerluver' Wrote: Modern tiger research has forgotten about the reports of populations in Borneo and maybe even the Philippines, at least they're not a point for discussion. Looking at the Sunda shelf, I took it for granted that tigers inhabited Borneo based on the current database. But a paper questioned the consensus but also pointed out supporting evidence, and I've attached it (Meihaard 1999).
Regardless, in my opinion, tigers should have at some point been on Borneo based on the findings a tiger on Palawan, a region between Borneo and the Philippines. Piper et al. (2008) cites two fossils dating from only 12 kya. The bones (phalanx) were slightly larger than the comparitive modern Indian and island tiger fossils. Interestingly, Javan tiger phalanx are slightly bigger than the Indian specimens compared. Although, the gender of the Indian tigers are unknown, and they may simply be females. From this, I think tigers that were of the P. t. sondaica subspecies likely survived until very recently on Borneo and the Philippines. Two fossils show something slightly larger than the Javan tiger, assuming the phalanx proportions were like the Javan form's oddly large paws.
I've also attached the Palawan paper. What do you guys think of the papers analyses?
Thanks for the links. The Palawan paper was printed. I got Meyaard's article from Dr. Van Bree.
As for the questions. There's no doubt tigers inhabited most of the Sunda Shelf, meaning they would have inhabited (parts of) Borneo and suited regions in the Philippines. When they had to move south as a result of the rising sea level and settled on the three Indonesian islands where they survived until half a century ago, they could have been a bit larger than today. Not as large as their Pleistocene ancestors, but similar in size to most continental tigers. My guess is Java tigers were their closest relatives.
Sumatrans adapted, because of the different circumstances. There's no question Sumatran tigers have slightly shorter skulls, but they did show more range in size. Could have been a sign of recent colonization. Sumatrans could have been somewhat stockier than Javan tigers. The 'problem' Sumatrans shown in a recent BBC-documentary, I think, are a result of the ongoing war on Sumatra.
RE: ON THE EDGE OF EXTINCTION - A - TIGERS (Panthera tigris) - tigerluver - 07-28-2015
Has anyone found a source providing concrete evidence of tigers in Japan?