What are everyone's opinions on subspecies conservation in zoo populations - specifically, in already threatened or endangered species?
This is something that interests me, and I don't intend to go against the tide if this view is not shared, but I think that that preserving every living endangered subspecies (in this example I think particularly of tigers) in isolation from one another is an arbitrary method of management that follows the false idea that nature must be preserved exactly as it is now, today, in the time we are currently living - when really life is in a constant state of genetic flux and has been since the beginning of life on Earth. It limits genetic diversity, particularly for those subspecies with very small captive populations (Sumatran tiger) - if Sumatrans are only bred to Sumatrans there are only going to be so many unrelated pairings possible before every living cat is a relative. This sounds like a recipe for problems.
Is it really better to keep populations, such as the Sumatran, Bengal, and Amur tigers, in reproductive isolation - at the risk of at least one of those subspecies possibly becoming weaker and more inbred? Why should they not be managed as a single much more diverse population - just tigers? Assuming that the difference between them is not so much as to result in outbreeding depression (as far as I know, not documented in tigers or lions) is this mixing of genes really a loss, or can it be a gain?
I have seen mentions many times of zoo-mix lions and Bengal tigers with Amur genes and how these animals are useless for conservation and all I can think is... why is this so? They are still lions and tigers, and if ever there was a time where we were going to reintroduce either species into the wild, a generic member of either species should carry all the genes of its predecessors and populations would be selected again into new races or subspecies in a relatively short time just as the ancestral, generic lion or tiger did, right?
The ecosystem of the future won't care if the lion on the plains has distant Asiatic ancestors, or if the Indian tiger had a great-grand-grandparent from Siberia, if it only needs a large predator to control herbivore numbers. It can be argued that pure subspecies are perfectly adapted to their specific region of origin, and this is true. The Sumatran tiger is small and adapted to the humid tropics, the Amur large and suited to boreal winters. But they are adapted to a world that is rapidly changing, to habitats that may soon no longer exist. In the best case scenario, the tigers of the future will not live in the world of their ancestors. Evolution demonstrates that in changing conditions, it is the generalist that survives, not the specialist.
Furthermore, at least as much of an influence on the adaptability of the animal seems to come from its environment as its genes; even the purest Amur tiger from the average zoo environment today would fail to hunt a boar or a moose without being taught by a competent mother tiger - a Sumatran cub, if fostered to a wild Amur mother would stand a greater chance. The Siberian's fur is thicker, but the Sumatran's also thickens in a cold climate, and the reverse is true for an Amur in a tropical area. I strongly suspect that either subspecies, lying at the extremes of size as they do, could survive over almost the entire range as all of the modern and recently extinct tiger subspecies did if they were somehow properly acclimated to local climate and prey. Granted, teaching hunting and self-sufficiency is a huge hurdle with any captive carnivore, but it would not be inherently simpler to teach a Sumatran tiger to hunt Sambar than to hunt sika. There is no genetic component to managing the specific prey of a given region and all must be learned anyway.
I know that Asian elephants in the United States are managed at species level due to the low population, but I think that there are other species which have already reached low enough levels that subspecific conservation should be abandoned. I would consider tigers among them, and I would also consider lions - though this really isn't a problem anymore considering that the majority of the lions in captivity are already mixed it does seem totally incorrect to label this whole population as useless to conservation just because they are not pedigreed. I would not currently condone releasing African genes into the Gir forest population at this time because that group is already beyond the carrying capacity of its environment, though the influx of genes would certainly benefit the population which right now is heavily inbred. However, if somehow, someway, space opened up to introduce lions somewhere else in Asia I would absolutely condone introducing a more vigorous generic zoo-mix group versus trying to spread the Asiatic remnants further. A few generations in the wild would already begin producing a new uniquely adapted land race, adapted not for a habitat of the past, but whatever habitats the future offers. Humans have drastically changed the world and the areas all of these animals come from, yet we are very determined to make sure the animals stay exactly the same as they were at the exact point of time we started to classify them. This goes against how nature operates, where there are no constants, no species, simply constant and relentless genetic change.
I feel the same about the wolf coyote complex between the coyote and the gray, Eastern, and red wolf. I feel we shouldn't be preserving the red wolf, it was an animal that evolved in a previous world, a world without man and arbitrary species borders, and it will not survive in a pure form today without human influence. But it can interbreed with the gray wolf and the coyote, and in a wild setting, some of their genes would go on, and the Canis genus as a whole would persist and rediversify as it has surely many times for hundreds of thousands of years.
I don't know enough about orangutans to make a judgment. The Bornean and Sumatran are now known to be genetically distinct, but how distinct are they? They are clearly cross fertile as dozens of zoo hybrids show, but whether out-breeding depression would develop as they in turn were bred unfortunately, we don't definitively know. If F2, F3 and further hybrid crosses proved to be prone to infertility or defect, I'd say halting the hybridization when we did was indeed the right thing. But I have to wonder if, given the dire state of the orangutan genus in the wild and the overall still rather small zoo populations, if allowing the two variations to merge to a single hybrid population would have improved their chances of long-term survival. Hybrid speciation is a documented occurrence, and is currently occurring with the gray wolf and coyote in the Eastern US and Galapagos finches.
Note, I am not condoning the automatic disregard for genetic diversity - if it were feasible to preserve ten varieties of something in captivity and the habitats each came from remain in the wild to reintroduce them back to, it would be wonderful. But this isn't the case with most large, endangered animals - tigers, Asian elephants, red wolves or orangutans. Zoos have limited space, and we almost certainly do not have the means to maintain healthy isolated populations of three tiger subspecies indefinitely without compromising the health of at least one (and with most of the captive Bengal population impure, this would leave us only with a small pure population of Amur tigers - each carrying but a fraction of the former diverse genes of the species) Our Ark is finite in capacity, and the wild habitats these animals came from may not be there when the time may come to let some animals go back to it anyway.
That is my view, anyway.
This is something that interests me, and I don't intend to go against the tide if this view is not shared, but I think that that preserving every living endangered subspecies (in this example I think particularly of tigers) in isolation from one another is an arbitrary method of management that follows the false idea that nature must be preserved exactly as it is now, today, in the time we are currently living - when really life is in a constant state of genetic flux and has been since the beginning of life on Earth. It limits genetic diversity, particularly for those subspecies with very small captive populations (Sumatran tiger) - if Sumatrans are only bred to Sumatrans there are only going to be so many unrelated pairings possible before every living cat is a relative. This sounds like a recipe for problems.
Is it really better to keep populations, such as the Sumatran, Bengal, and Amur tigers, in reproductive isolation - at the risk of at least one of those subspecies possibly becoming weaker and more inbred? Why should they not be managed as a single much more diverse population - just tigers? Assuming that the difference between them is not so much as to result in outbreeding depression (as far as I know, not documented in tigers or lions) is this mixing of genes really a loss, or can it be a gain?
I have seen mentions many times of zoo-mix lions and Bengal tigers with Amur genes and how these animals are useless for conservation and all I can think is... why is this so? They are still lions and tigers, and if ever there was a time where we were going to reintroduce either species into the wild, a generic member of either species should carry all the genes of its predecessors and populations would be selected again into new races or subspecies in a relatively short time just as the ancestral, generic lion or tiger did, right?
The ecosystem of the future won't care if the lion on the plains has distant Asiatic ancestors, or if the Indian tiger had a great-grand-grandparent from Siberia, if it only needs a large predator to control herbivore numbers. It can be argued that pure subspecies are perfectly adapted to their specific region of origin, and this is true. The Sumatran tiger is small and adapted to the humid tropics, the Amur large and suited to boreal winters. But they are adapted to a world that is rapidly changing, to habitats that may soon no longer exist. In the best case scenario, the tigers of the future will not live in the world of their ancestors. Evolution demonstrates that in changing conditions, it is the generalist that survives, not the specialist.
Furthermore, at least as much of an influence on the adaptability of the animal seems to come from its environment as its genes; even the purest Amur tiger from the average zoo environment today would fail to hunt a boar or a moose without being taught by a competent mother tiger - a Sumatran cub, if fostered to a wild Amur mother would stand a greater chance. The Siberian's fur is thicker, but the Sumatran's also thickens in a cold climate, and the reverse is true for an Amur in a tropical area. I strongly suspect that either subspecies, lying at the extremes of size as they do, could survive over almost the entire range as all of the modern and recently extinct tiger subspecies did if they were somehow properly acclimated to local climate and prey. Granted, teaching hunting and self-sufficiency is a huge hurdle with any captive carnivore, but it would not be inherently simpler to teach a Sumatran tiger to hunt Sambar than to hunt sika. There is no genetic component to managing the specific prey of a given region and all must be learned anyway.
I know that Asian elephants in the United States are managed at species level due to the low population, but I think that there are other species which have already reached low enough levels that subspecific conservation should be abandoned. I would consider tigers among them, and I would also consider lions - though this really isn't a problem anymore considering that the majority of the lions in captivity are already mixed it does seem totally incorrect to label this whole population as useless to conservation just because they are not pedigreed. I would not currently condone releasing African genes into the Gir forest population at this time because that group is already beyond the carrying capacity of its environment, though the influx of genes would certainly benefit the population which right now is heavily inbred. However, if somehow, someway, space opened up to introduce lions somewhere else in Asia I would absolutely condone introducing a more vigorous generic zoo-mix group versus trying to spread the Asiatic remnants further. A few generations in the wild would already begin producing a new uniquely adapted land race, adapted not for a habitat of the past, but whatever habitats the future offers. Humans have drastically changed the world and the areas all of these animals come from, yet we are very determined to make sure the animals stay exactly the same as they were at the exact point of time we started to classify them. This goes against how nature operates, where there are no constants, no species, simply constant and relentless genetic change.
I feel the same about the wolf coyote complex between the coyote and the gray, Eastern, and red wolf. I feel we shouldn't be preserving the red wolf, it was an animal that evolved in a previous world, a world without man and arbitrary species borders, and it will not survive in a pure form today without human influence. But it can interbreed with the gray wolf and the coyote, and in a wild setting, some of their genes would go on, and the Canis genus as a whole would persist and rediversify as it has surely many times for hundreds of thousands of years.
I don't know enough about orangutans to make a judgment. The Bornean and Sumatran are now known to be genetically distinct, but how distinct are they? They are clearly cross fertile as dozens of zoo hybrids show, but whether out-breeding depression would develop as they in turn were bred unfortunately, we don't definitively know. If F2, F3 and further hybrid crosses proved to be prone to infertility or defect, I'd say halting the hybridization when we did was indeed the right thing. But I have to wonder if, given the dire state of the orangutan genus in the wild and the overall still rather small zoo populations, if allowing the two variations to merge to a single hybrid population would have improved their chances of long-term survival. Hybrid speciation is a documented occurrence, and is currently occurring with the gray wolf and coyote in the Eastern US and Galapagos finches.
Note, I am not condoning the automatic disregard for genetic diversity - if it were feasible to preserve ten varieties of something in captivity and the habitats each came from remain in the wild to reintroduce them back to, it would be wonderful. But this isn't the case with most large, endangered animals - tigers, Asian elephants, red wolves or orangutans. Zoos have limited space, and we almost certainly do not have the means to maintain healthy isolated populations of three tiger subspecies indefinitely without compromising the health of at least one (and with most of the captive Bengal population impure, this would leave us only with a small pure population of Amur tigers - each carrying but a fraction of the former diverse genes of the species) Our Ark is finite in capacity, and the wild habitats these animals came from may not be there when the time may come to let some animals go back to it anyway.
That is my view, anyway.
and the native subspecies is likely to still exist, even if the exact genetic subpopulation does not.
