Do you work with bison, or other livestock?
Generic and Hybrid Populations in Zoos
- Thread starter JVM
- Start date
Do you work with bison, or other livestock?
I suspect some of this is because, in my experience, some zoochatters don't consider these splits valid and therefore are not as concerned about "hybridization" in that view. I also think some of it is because while the giraffe and ostrich situations have been known for many years, some of these splits are too recent to expect major changes to the population. I know when it was discussed that the common chimpanzee population is fairly mixed, zoochatters seemed to collectively shrug and accept it would just be too difficult a problem to fix.
I almost wish there was a good 'history of taxonomy' document that compared each primate group's classification x years ago to the present splits.
I have a feeling this probably sounds a little sarcastic but isn't intended! I don't know any better about this stuff than the people who I'm reading from.
iloveyourzoos
Well-Known Member
I guess I'm wondering whether the zoo community is working on any policies or practices to think proactively or preemptively or holistically about the challenge of future taxonomic changes and splits, or whether we are understandably too busy (at a practical level) just trying to keep up and respond after a scientific split has happened.
So much of modern zoos' focus on both conservation and population management is built upon the current understandings and definitions of species and subspecies. (And rightly so!). But I'm wondering if there are some visionaries who see the rapid number of taxonomic changes, who predict that those changes are likely to continue or even increase, and who therefore are sounding an alarm about building our programs and institutions on metaphorical quicksand (ie. on taxonomic systems that may be vastly different 10 or 20 or 50 or 100 years from now). And/or who are proposing alternatives that might be able to outlast and survive those changes, regardless of what they may be.
[Note: I suspect that part of the answer may be that I'm vastly overestimating the scale of the problem and how often these taxonomic changes actually happen, since change always garners more publicity and more discussion than stability does. But I'd still be interested in whether any proactive planning is being done about what to do when such taxonomic changes do inevitably occur -- both for unexpected changes that may arise suddenly, as well as for species or genera where we already know or suspect that the taxonomy we're using isn't completely settled.]
So much of modern zoos' focus on both conservation and population management is built upon the current understandings and definitions of species and subspecies. (And rightly so!). But I'm wondering if there are some visionaries who see the rapid number of taxonomic changes, who predict that those changes are likely to continue or even increase, and who therefore are sounding an alarm about building our programs and institutions on metaphorical quicksand (ie. on taxonomic systems that may be vastly different 10 or 20 or 50 or 100 years from now). And/or who are proposing alternatives that might be able to outlast and survive those changes, regardless of what they may be.
[Note: I suspect that part of the answer may be that I'm vastly overestimating the scale of the problem and how often these taxonomic changes actually happen, since change always garners more publicity and more discussion than stability does. But I'd still be interested in whether any proactive planning is being done about what to do when such taxonomic changes do inevitably occur -- both for unexpected changes that may arise suddenly, as well as for species or genera where we already know or suspect that the taxonomy we're using isn't completely settled.]
I think it varies a lot across the scope of species. At this point there's generally a build-up to species splits becoming official, as testing is done and evidence is found to support (or reject) ideas. For some, zoos are working one step ahead - look at giraffes, for example. King cobras are another one. There's a big split coming, there's been papers leading up to it, and AZA has been figuring out which zoos have which kinds and what ones they want to work with moving forward. It also depends a lot on the population, too. Using giraffes again, they've been around so long and have been so interbred that trying to separate into species/subspecies was completely hopeless, except for Masai. Most king cobras are more recent imports, though, and are much more likely to be pure.
That might be the case over on your side of the puddle, but over here zoological collections have the matter firmly in hand, with a decent number of purebred breeding groups of verus and troglodytes having been discovered or created - and with pure animals of the other two subspecies also having been located in the process.
It helps that quite a few of the King Cobra in private and public hands (both in Europe and North America) originally came from the private collection of Luke Yeomans, who did quite a bit of work on the subject and kept/bred multiple of the upcoming species before his untimely passing in 2011.... so those collections which ended up with his animals had a head start in knowing what precisely they have!
That's good to know, and I'm glad to know it has been sorted over there. when the topic came up in a US thread and I looked for Europe information, it was several years out of date but suggested a similar predicament with research still unfinished. It does make a lot of sense though - it does sound like Europe has more interest in managing chimpanzees than the United States has recently.
This is an interesting discussion; we can be far too purist about maintaining subspecific purity especially for those that are clinal and where there is probably much introgression. Introducing a mix of races to the wild, and hence much genetic variation, can be advantageous. I like the example of the Peregrine Falcon in North America where several different races were introduced to replace a lost population and to allow natural selection to mould the medley of sub-species into a bird suitable for the area.
The Peregrine Falcon from the eastern states of North America became extirpated by the late 1960’s. These falcons were a distinct eastern form of the race anatum, and although anatum Peregrines still existed in the Western states these birds were separated by the prairies and were phenotypically, and presumably genetically, distinct. The eastern anatum Peregrines were larger, darker, more extensively marked and with a more rufous suffusion on the breast.
A captive breeding programme was established using birds of several different races although about 70% of these were of three North American races, the relatively small pale Tundra Peregrine tundrius, the western anatum and the large dark maritime Peale’s Peregrine pealii. A small number of other races were included including about 18% Mediterranean Peregrines brookei from Spain and a small number of the nominate form from Scotland, some South American Peregrine Falcons cassini and even a few Australian Peregrines macropus.
The logic behind the introduction of a mix of races was so that natural selection would have variety on which to operate. In time this population may revert to birds that are phenotypically inseparable from the original eastern anatum Peregrines. This will probably take 30-50 generations before there will be any analysable quantifiable changes within the population. Already (after about >10 generations) there are signs that natural selection is already showing obvious impacts, and the large dark Peale’s Peregrines have largely died out, and there are birds phenotypically close to the original eastern anatum peregrines.
This case raises many interesting questions, and it will be important to see how this population progresses. How the relative proportions of genotypes and phenotypes change over time? If there is convergence back to the original eastern anatum peregrines, as most expect, this will provide good evidence that in restoration programmes one can be liberal regarding the sanctity of races. However, others are suggesting that with such a diverse gene pool, and since Eastern United States is now such a different environment to the one in which the eastern anatum evolved then a novel regional gene pool will be created, and a new phenotype will develop that reflects relatively stable and adaptive gene frequencies.
The Peregrine Falcon from the eastern states of North America became extirpated by the late 1960’s. These falcons were a distinct eastern form of the race anatum, and although anatum Peregrines still existed in the Western states these birds were separated by the prairies and were phenotypically, and presumably genetically, distinct. The eastern anatum Peregrines were larger, darker, more extensively marked and with a more rufous suffusion on the breast.
A captive breeding programme was established using birds of several different races although about 70% of these were of three North American races, the relatively small pale Tundra Peregrine tundrius, the western anatum and the large dark maritime Peale’s Peregrine pealii. A small number of other races were included including about 18% Mediterranean Peregrines brookei from Spain and a small number of the nominate form from Scotland, some South American Peregrine Falcons cassini and even a few Australian Peregrines macropus.
The logic behind the introduction of a mix of races was so that natural selection would have variety on which to operate. In time this population may revert to birds that are phenotypically inseparable from the original eastern anatum Peregrines. This will probably take 30-50 generations before there will be any analysable quantifiable changes within the population. Already (after about >10 generations) there are signs that natural selection is already showing obvious impacts, and the large dark Peale’s Peregrines have largely died out, and there are birds phenotypically close to the original eastern anatum peregrines.
This case raises many interesting questions, and it will be important to see how this population progresses. How the relative proportions of genotypes and phenotypes change over time? If there is convergence back to the original eastern anatum peregrines, as most expect, this will provide good evidence that in restoration programmes one can be liberal regarding the sanctity of races. However, others are suggesting that with such a diverse gene pool, and since Eastern United States is now such a different environment to the one in which the eastern anatum evolved then a novel regional gene pool will be created, and a new phenotype will develop that reflects relatively stable and adaptive gene frequencies.
While this sounds like an interesting program, I think that the conservation implications of "generic" populations is likely dependent on what morphological and behavioral traits are different in the subspecies. In a case like the falcons, I suspect those results were achieved because the main trait you're describing as different is pelage, and there was high variability in this trait to enable natural selection. I'd imagine other cases of pelage being the main difference could occur in a similar fashion- for instance I doubt it'd matter if zoos released the "wrong" red panda subspecies in an area.
However, in cases that subspecies have some other, more substantial differences, I'm skeptical this approach could work. For example, tigers and leopards where cold/heat tolerance is one of the major differences between the subspecies. There are no circumstances where a Sumatran tiger would survive in Siberia, and similarly no circumstances where an Amur tiger would survive in Sumatra, so releasing the "wrong" subspecies (or an individual with a lot of the traits of the wrong subspecies) would essentially be a waste of individuals. That said, even if a generic population doesn't have any conservation value, that is not to say there isn't any education or research value to keeping them in zoos, and the majority of zoo populations are not (and likely will never be) tied to re-introduction programs anyways.
Neil raises some interesting points. In the Peregrine Falcon example the different races will show differences in temperature tolerances and ability to live in areas with different levels of precipitation. The darkness of the plumage being related to the level of precipitation. There are differences in size and also proportions. Some of the subspecies involved were quite distinctive.
The point raised that most (generic) zoo populations will never be used for reintroductions is correct.
The point raised that most (generic) zoo populations will never be used for reintroductions is correct.